Rhinoceros, often abbreviated as rhino, is a group of five extant species of knee-less, odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia(HP Pavilion dv4 battery).

Members of the rhinoceros family are characterized by their large size (they are some of of the largest remaining megafauna, with all of the species able to reach one tonne or more in weight); as well as by a herbivorous diet; a thick protective skin, 1.5–5 cm thick, formed from layers of collagen positioned in a lattice structure; relatively small brains for mammals this size (HP PAVILION DV4000 battery) (400–600 g); and a large horn. They generally eat leafy material, although their ability to ferment food in their hindgut allows them to subsist on more fibrous plant matter, if necessary. Unlike other perissodactyls, the African species of rhinoceros lack teeth at the front of their mouths, relying instead on their powerful premolar and molar teeth to grind up plant food. (HP Pavilion dv5-1000 battery)

Rhinoceros are killed by humans for their horns, which are bought and sold on the black market, and which are used by some cultures for ornamental or (pseudo-scientific) medicinal purposes. The horns are made of keratin, the same type of protein that makes up hair and fingernails.[2] Both African species and the Sumatran rhinoceros have two horns, while the Indian and Javan rhinoceros have a single horn(HP Pavilion dv6 battery).

The IUCN Red List identifies three of the species as critically endangered.

Taxonomy and naming

Comparison between living rhinoceroses species.

The word rhinoceros is derived through Latin from the Ancient Greek: ῥῑνόκερως, which is composed of ῥῑνο- (rhino-, "nose") and κέρας (keras, "horn"). The plural in English is rhinoceros or rhinoceroses. The collective noun for a group of rhinoceroses is crash or herd(HP Pavilion DV6-1210SA battery).

The five living species fall into three categories. The two African species, the white rhinoceros and the black rhinoceros, diverged during the early Pliocene (about 5 million years ago) but the Dicerotini group to which they belong originated in the middle Miocene, about 14.2 million years ago. The main difference between black and white rhinos is the shape of their mouths(HP Pavilion dv6000 battery). White rhinos have broad flat lips for grazing and black rhinos have long pointed lips for eating foliage. A popular — if unverified — theory claims that the name white rhinoceros was actually a mistake, or rather a corruption of the word weid ("wide" in Afrikaans), referring to their square lips. (HP Pavilion dv6200 battery)

White rhinoceros are divided into northern and southern subspecies. There are two living Rhinocerotini species, the Indian rhinoceros and the Javan rhinoceros, which diverged from one another about 10 million years ago. The Sumatran rhinoceros is the only surviving representative of the most primitive group, the Dicerorhinini, which emerged in the Miocene (about 20 million years ago). (HP Pavilion dv6500 battery)The extinct woolly rhinoceros of northern Europe and Asia was also a member of this tribe.

A subspecific hybrid white rhino (Ceratotherium s. simum × C. s. cottoni) was bred at the Dvůr Králové Zoo (Zoological Garden Dvur Kralove nad Labem) in the Czech Republic in 1977. Interspecific hybridisation of black and white rhinoceros has also been confirmed. (HP Pavilion dv8000 battery)

All rhinoceros species have 82 chromosomes (diploid number, 2N, per cell), except the black rhinoceros, which has 84.

The five extant species

The white rhinoceros is actually grey

The black rhinoceros has a beak shaped lip and is similar in color to the white rhinoceros

The Indian rhinoceros has a single horn

Smaller in size than the Indian rhinoceros, the Javan rhinoceros also have a single horn

The Sumatran rhinoceros is the smallest of the rhino species(HP Pavilion dv9000 battery)

White rhinoceros

Main article: White rhinoceros

There are two subspecies of white rhinos; as of 2005, South Africa has the most of the first subspecies, the southern white rhinoceros (Ceratotherium simum simum). The population of southern white rhinos is about 14,500, making them the most abundant subspecies of rhino in the world. However, the population of the second subspecies, the critically endangered northern white rhinoceros (Ceratotherium simum cottoni) (HP Pavilion dv9200 battery), is down to as few as four individuals in the wild, with the possibility of complete extinction in the wild having been noted since June 2008.[6] Six are known to be held in captivity, two of which reside in a zoo in San Diego. There are currently four born in a zoo in the Czech Republic which were transferred to a wildlife refuge in Kenya in December 2009, in an effort to have the animals reproduce and save the subspecies. (HP Pavilion dv9500 battery)

There is no conclusive explanation of the name white rhinoceros. A popular theory that "white" is a distortion of the Dutch word wijd (or its other possible spellings whyde, weit, etc., all meaning wide) is not supported by linguistic studies.[8]

The white rhino has an immense body and large head, a short neck and broad chest. This rhino can exceed 3,500 kg (7,700 lb), have a head-and-body length of 3.5–4.6 m (11–15 ft) and a shoulder height of 1.8–2 m (5.9–6.6 ft) (HP Pavilion dv9700 battery). The record-sized white rhinoceros was about 4,500 kg (10,000 lb).[9] On its snout it has two horns. The front horn is larger than the other horn and averages 90 cm (35 in) in length and can reach 150 cm (59 in). The white rhinoceros also has a prominent muscular hump that supports its relatively large head. The colour of this animal can range from yellowish brown to slate grey(HP Pavilion dv6-3000 battery). Most of its body hair is found on the ear fringes and tail bristles with the rest distributed rather sparsely over the rest of the body. White rhinos have the distinctive flat broad mouth which is used for grazing.

Black rhinoceros

Main article: Black rhinoceros

The name black rhinoceros (Diceros bicornis) was chosen to distinguish this species from the white rhinoceros (Ceratotherium simum). This can be confusing, as those two species are not really distinguishable by color(HP Pavilion dv6-3005sa battery). There are four subspecies of black rhino: South-central (Diceros bicornis minor), the most numerous, which once ranged from central Tanzania south through Zambia, Zimbabwe and Mozambique to northern and eastern South Africa; South-western (Diceros bicornis bicornis) which are better adapted to the arid and semi-arid savannas of Namibia, southern Angola(HP Pavilion dv6-3005tx battery), western Botswana and western South Africa; East African (Diceros bicornis michaeli), primarily in Tanzania; and West African (Diceros bicornis longipes) which was declared extinct in November 2011.[10] The native Tswanan name Keitloa is used to describe a South African variation of the black rhino in which the posterior horn is equal to or longer than the anterior horn. (HP Pavilion dv6-3006tx battery)

An adult black rhinoceros stands 150–175 cm (59–69 in) high at the shoulder and is 3.5–3.9 m (11–13 ft) in length.[12] An adult weighs from 850 to 1,600 kg (1,900 to 3,500 lb), exceptionally to 1,800 kg (4,000 lb), with the females being smaller than the males. Two horns on the skull are made of keratin with the larger front horn typically 50 cm long, exceptionally up to 140 cm(HP Pavilion dv6-3011tx battery). Sometimes, a third smaller horn may develop. The black rhino is much smaller than the white rhino, and has a pointed mouth, which they use to grasp leaves and twigs when feeding.

During the latter half of the 20th century their numbers were severely reduced from an estimated 70,000[13] in the late 1960s to only 2,410 in 1995.[14]

Indian rhinoceros

Main article: Indian rhinoceros

The Indian rhinoceros or the greater one-horned rhinoceros (Rhinoceros unicornis) is now found almost exclusively in Nepal and North-Eastern India(HP Pavilion dv6-3010sa battery). The rhino once inhabited many areas of Pakistan to Burma and may have even roamed in China. But because of human influence their range has shrunk and now they only exist in several protected areas of India (in Assam, West Bengal, Gujarat and a few pairs in Uttar Pradesh) and Nepal, plus a few pairs in Lal Suhanra National Park in Pakistan. It is confined to the tall grasslands and forests in the foothills of the Himalayas(HP Pavilion dv6-3015sa battery).

The Indian rhinoceros has thick, silver-brown skin which creates huge folds all over its body. Its upper legs and shoulders are covered in wart-like bumps, and it has very little body hair. Fully grown males are larger than females in the wild, weighing from 2,500–3,200 kg (5,500–7,100 lb).The Indian rhino stands at 1.75–2.0 metres (5.75–6.5 ft)(HP Pavilion dv6-3020sa battery). Female Indian rhinos weigh about 1,900 kg and are 3–4 metres long. The record-sized specimen of this rhino was approximately 3,800 kg. The Indian rhino has a single horn that reaches a length of between 20 and 100 cm. Its size is comparable to that of the white rhino in Africa.

Two-thirds of the world's Indian rhinoceroses are now confined to the Kaziranga National Park situated in the Golaghat district of Assam, India. (HP Pavilion dv6-3025sa battery)

Javan rhinoceros

Main article: Javan rhinoceros

The Javan rhinoceros (Rhinoceros sondaicus) is one of the rarest and most endangered large mammals anywhere in the world.[16] According to 2002 estimates, only about 60 remain, in Java (Indonesia) and Vietnam. Of all the rhino species, the least is known of the Javan Rhino. These animals prefer dense lowland rain forest, tall grass and reed beds that are plentiful with large floodplains and mud wallows(HP Pavilion dv6-3026tx battery). Though once widespread throughout Asia, by the 1930s the rhinoceros was nearly hunted to extinction in India, Burma, Peninsular Malaysia, and Sumatra for the supposed medical powers of its horn and blood. As of 2009, there are only 40 of them remaining in Ujung Kulon Conservation, Java, Indonesia. The last rhinoceros in Vietnam was reportedly killed in 2010. (HP Pavilion dv6-3030sa battery)

Like the closely related larger Indian rhinoceros, the Javan rhinoceros has only a single horn. Its hairless, hazy gray skin falls into folds into the shoulder, back, and rump giving it an armored-like appearance. The Javan rhino's body length reaches up to 3.1–3.2 m (10–10 ft), including its head and a height of 1.5–1.7 m (4 ft 10 in–5 ft 7 in) tall. Adults are variously reported to weigh between 900–1,400 kg[18] or 1,360–2,000 kg. (HP Pavilion dv6-3030tx battery)Male horns can reach 26 cm in length while in females they are knobs or are not present at all.[19]

Sumatran rhinoceros

Main article: Sumatran rhinoceros

The Sumatran rhinoceros (Dicerorhinus sumatrensis) is the smallest extant rhinoceros species, as well as the one with the most fur, which allows it to survive at very high altitudes in Borneo and Sumatra. Due to habitat loss and poaching, its numbers have declined and it is the most threatened rhinoceros. About 275 Sumatran rhinos are believed to remain(HP Pavilion dv6-3031sa battery).

Typically a mature Sumatran rhino stands about 130 cm (51 in) high at the shoulder, a body length of 240–315 cm (94–124 in) and weighs around 700 kg (1,500 lb), though the largest individuals have been known to weigh as much as 1,000 kilograms. Like the African species, it has two horns; the larger is the front (25–79 cm) (HP Pavilion dv6-3032sa battery), with the smaller second usually less than 10 cm long. The males have much larger horns than the females. Hair can range from dense (the densest hair in young calves) to scarce. The color of these rhinos is reddish brown. The body is short and has stubby legs. They also have a prehensile lip.

Evolution

The thick dermal armour of the Rhinoceros evolved at the same time as shearing tusks(HP Pavilion dv6-3032tx battery)

Rhinocerotoids diverged from other perissodactyls by the early Eocene. Fossils of Hyrachyus eximus found in North America date to this period. This small hornless ancestor resembled a tapir or small horse more than a rhino. Three families, sometimes grouped together as the superfamily Rhinocerotoidea, evolved in the late Eocene: Hyracodontidae, Amynodontidae and Rhinocerotidae(HP Pavilion dv6-3033sa battery).

Hyracodontidae, also known as 'running rhinos', showed adaptations for speed, and would have looked more like horses than modern rhinos. The smallest hyracodontids were dog-sized; the largest was Indricotherium, believed to be one of the largest land mammals that ever existed. The hornless Indricotherium was almost seven metres high, ten metres long(HP Pavilion dv6-3035sa battery), and weighed as much as 15 tons. Like a giraffe, it ate leaves from trees. The hyracodontids spread across Eurasia from the mid-Eocene to early Miocene.

The family Amynodontidae, also known as "aquatic rhinos", dispersed across North America and Eurasia, from the late Eocene to early Oligocene. The amynodontids were hippopotamus-like in their ecology and appearance, inhabiting rivers and lakes, and sharing many of the same adaptations to aquatic life as hippos(HP Pavilion dv6-3040sa battery).

The family of all the modern rhinoceros, the Rhinocerotidae, first appeared in the Late Eocene in Eurasia. The earliest members of Rhinocerotidae were small and numerous; at least 26 genera lived in Eurasia and North America until a wave of extinctions in the middle Oligocene wiped out most of the smaller species. Several independent lineages survived, however(HP Pavilion dv6-3042tx battery). Menoceras, a pig-sized rhinoceros had two horns side-by-side and Teleoceras of North America had short legs and a barrel chest and lived until about 5 million years ago. The last rhinos in the Americas became extinct during the Pliocene.

Modern rhinos are believed to have dispersed from Asia beginning in the Miocene. Two species survived the most recent period of glaciation and inhabited Europe as recently as 10,000 years ago(HP Pavilion dv6-3044sa battery). The woolly rhinoceros appeared in China around 1 million years ago and first arrived in Europe around 600,000 years ago and again 200,000 years ago, where alongside the woolly mammoth, they became numerous but eventually were hunted to extinction by early humans. Another species of enormous rhino, Elasmotherium, survived through the middle Pleistocene(HP Pavilion dv6-3045sa battery). Also known as the giant rhinoceros, Elasmotherium was two meters tall, five meters long and weighed around five tons, with a single enormous horn, hypsodont teeth and long legs for running.

Of the extant rhinoceros species, the Sumatran rhino is the most archaic, first emerging more than 15 million years ago. The Sumatran rhino was closely related to the woolly rhinoceros, but not to the other modern species(HP Pavilion dv6-3046sa battery). The Indian rhino and Javan rhino are closely related and from a more recent lineage of Asian rhino. The ancestors of early Indian and Javan rhino diverged 2–4 million years ago.[21]

The origin of the two living African rhinos can be traced back to the late Miocene (6 mya) species Ceratotherium neumayri. The lineages containing the living species diverged by the early Pliocene (1.5 mya), when Diceros praecox, the likely ancestor of the black rhinoceros, appears in the fossil record. (HP Pavilion dv6-3047sa battery)The black and white rhinoceros remain so closely related that they can still mate and successfully produce offspring.[5]

Predators

Monk with rhinoceros horn. Samye, Tibet, 1938.

In the wild, adult rhinoceros have few natural predators other than humans. Young rhinos can fall prey to predators such as big cats, crocodiles, wild dogs, and hyena. Although rhinos are of large size and have a reputation of being tough, they are actually very easily poached, because it visits water holes daily, the rhinoceros is easily killed while taking a drink(HP Pavilion dv6-3048sa battery). As of December 2009 poaching has been on a global increase whilst efforts to protect the rhinoceros are being considered increasingly ineffective. The worst estimate, that only 3% of poachers are successfully countered, is reported of Zimbabwe. Rhino horn is considered to be particularly effective on fevers and even "life saving" by traditional Chinese medicine practitioners(HP Pavilion dv6-3048tx battery), which in turn provides a sales market. Nepal is apparently alone in avoiding the crisis while poacher-hunters grow ever more sophisticated.[26] South African officials are calling for urgent action against rhinoceros poaching after poachers killed the last female rhinoceros in the Krugersdorp Game Reserve near Johannesburg.[27] Statistics from South African National Parks show a record 333 rhinoceros have been killed in 2010(HP Pavilion dv6-3050eo battery).

Horns

Rhinoceros horns, unlike those of other horned mammals, consist of keratin only and lack a bony core, such as bovine horns. Rhinoceros horns are used in traditional Asian medicine, and for dagger handles in Yemen and Oman. Esmond Bradley Martin has reported on the trade for dagger handles in Yemen. (HP Pavilion dv6-3050sa battery)

One repeated misconception is that rhinoceros horn in powdered form is used as an aphrodisiac in Traditional Chinese Medicine (TCM) as Cornu Rhinoceri Asiatici (犀角). It is, in fact, prescribed for fevers and convulsions.[30] Neither have been proven by evidence-based medicine. Discussions with TCM practitioners to reduce its use have met with mixed results since some TCM doctors see rhinoceros horn as a life-saving medicine of better quality than substitutes.(HP Pavilion dv6-3055sa battery) China has signed the CITES treaty however, and removed rhinoceros horn from the Chinese medicine pharmacopeia, administered by the Ministry of Health, in 1993. In 2011 in the United Kingdom, the Register of Chinese Herbal Medicine issued a formal statement condemning the use of rhinoceros horn.[32] A growing number of TCM educators have also spoken out against the practice. (HP Pavilion dv6-3056sa battery) To prevent poaching, in certain areas, rhinos have been tranquilized and their horns removed. Armed park rangers, particularly in South Africa, are also working on the front lines to combat poaching, sometimes killing poachers who are caught in the act. A recent spike in rhino killings has made conservationaists concerned about the future of rhino species(HP Pavilion dv6-3057sa battery). During 2011 448 rhino were killed for their horn in South Africa alone.[34] The horn is incredibly valuable: an average sized horn can bring in much as a quarter of a million dollars in Vietnam and many rhino range States have stockpiles of rhino horn. Still, poaching is hitting record levels due to demands from China and Vietnam.(HP Pavilion dv6-3060sa battery)

Historical representations

Albrecht Dürer created a famous woodcut of a rhinoceros in 1515, based on a written description and brief sketch by an unknown artist of an Indian rhinoceros that had arrived in Lisbon earlier that year. Dürer never saw the animal itself, and as a result, Dürer's Rhinoceros is a somewhat inaccurate depiction(HP Pavilion dv6-3065ea battery).

There are legends about rhinoceros stamping out fire in Malaysia, India, and Burma. The mythical rhinoceros has a special name in Malay, badak api, where badak means rhinoceros and api means fire. The animal would come when a fire is lit in the forest and stamp it out.[38] There are no recent confirmations of this phenomenon. However, this legend has been reinforced by the film The Gods Must Be Crazy, where an African rhinoceros is shown to be putting out two campfires. (HP Pavilion dv6-3067ea battery)

The hippopotamus (Hippopotamus amphibius), or hippo, from the ancient Greek for "river horse" (ἱπποπόταμος), is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae (the other is the Pygmy Hippopotamus.) After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest extant artiodactyl(HP Pavilion dv6-3068ea battery).

The hippopotamus is semi-aquatic, inhabiting rivers, lakes and mangrove swamps, where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day they remain cool by staying in the water or mud; reproduction and childbirth both occur in water. They emerge at dusk to graze on grass. While hippopotamuses rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land(HP Pavilion dv6-3070ea battery).

Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, their closest living relatives are cetaceans (whales, porpoises, etc.) from which they diverged about 55 million years ago.[3] The common ancestor of whales and hippos split from other even-toed ungulates around 60 million years ago.[4] The earliest known hippopotamus fossils, belonging to the genus Kenyapotamus in Africa, date to around 16 million years ago(HP Pavilion dv6-3077la battery).

The hippopotamus is recognizable by its barrel-shaped torso, enormous mouth and teeth, nearly hairless body, stubby legs and tremendous size. It is the third largest land mammal by weight (between 1½ and 3 tonnes), behind the white rhinoceros (1½ to 3½ tonnes) and the three species of elephant (3 to 9 tonnes). The hippopotamus is one of the largest quadrupeds (four legged mammals) [5] and despite its stocky shape and short legs(HP Pavilion dv6-3085ea battery), it can easily outrun a human. Hippos have been clocked at 30 km/h (19 mph) over short distances. The hippopotamus is one of the most aggressive creatures in the world and is often regarded as one of the most dangerous animals in Africa. There are an estimated 125,000 to 150,000 hippos throughout Sub-Saharan Africa; Zambia (40,000) and Tanzania (20,000–30,000) possess the largest populations. (HP Pavilion dv6-3100 battery)They are still threatened by habitat loss and poaching for their meat and ivory canine teeth. There is also a colony of non-zoo hippos in Colombia introduced by Pablo Escobar.

Etymology

Look up hippopotamus in Wiktionary, the free dictionary.

The word "hippopotamus" is derived from the ancient Greek ἱπποπόταμος, hippopotamos, from ἵππος, hippos, "horse", and ποταμός, potamos, "river", meaning "horse of the river".[6] In English, the plural is hippopotamuses, but hippopotami is also used; (HP Pavilion dv6-3100sa battery) hippos can be used as a short plural. Hippopotamuses are gregarious, living in groups of up to 30 animals; such a name is called a pod, herd, dale, or bloat.

In Africa, the hippo is known by several names including Kiboko (Swahili), Ensherre (Nkore), Tomondo (Turu), Nvubu (Luganda), Ifuru (Luhya), Emiria (Ateso), Magawit (Sebei), Kibei (Kalenjin), Olmakau (Maasai) and Jir (Somali) in the east;[8]:256 and Seekoei (Afrikaans), Mvuvu (Venda), Kubu (Lozi) and Mvubu (Xhosa, Siswati and Zulu) in the south. (HP Pavilion dv6-3110ea battery)

Taxonomy and origins

Classification

The hippopotamus is the type genus of the family Hippopotamidae. The Pygmy Hippopotamus belongs to a different genus in Hippopotamidae, either Choeropsis or Hexaprotodon. Hippopotamidae are sometimes known as Hippopotamids. Sometimes the sub-family Hippopotaminae is used. Further, some taxonomists group hippopotamuses and anthracotheres in the super-family Anthracotheroidea or Hippopotamoidea(HP Pavilion dv6-3110sa battery).

A pygmy hippopotamus (Hexaprotodon liberiensis)

Hippopotamidae are classified along with other even-toed ungulates in the order Artiodactyla. Other artiodactyls include camels, cows, deer and pigs, although hippopotamuses are not closely related to these groups.

Five subspecies of hippos have been described based on morphological differences in their skulls and geographical differences: (HP Pavilion dv6-3111sa battery)

H. a. amphibius – (the nominate subspecies) which stretched from Egypt, where they are now extinct, south up the Nile River to Tanzania and Mozambique.

H. a. kiboko – in the Horn of Africa, in Kenya and Somalia. Broader nasals and more hollowed interorbital region.

H. a. capensis – from Zambia to South Africa. Most flattened skull of the subspecies(HP Pavilion dv6-3112sa battery).

H. a. tschadensis – throughout Western Africa to, as the name suggests, Chad. Slightly shorter and wider face, with prominent orbits.

H. a. constrictus – in Angola, the southern Democratic Republic of Congo and Namibia. Named for its deeper preorbital constriction.

The suggested subspecies were never widely used or validated by field biologists; the described morphological differences were small enough that they could have resulted from simple variation in non-representative samples. (HP Pavilion dv6-3113sa battery)Genetic analyses have tested the existence of three of these putative subspecies. A study examining mitochondrial DNA from skin biopsies taken from 13 sampling locations, considered genetic diversity and structure among hippo populations across the continent. The authors found low but significant genetic differentiation among H. a. amphibius, H. a. capensis, and H. a. kiboko. Neither H.a.tschadensis nor H.a.constrictus have been tested. (HP Pavilion dv6-3114sa battery)

[edit]Evolution

Until 1909, naturalists grouped hippos with pigs, based on molar patterns. Several lines of evidence, first from blood proteins, then from molecular systematics[14] and DNA [15][16] and the fossil record, show that their closest living relatives are cetaceans—whales, dolphins and porpoises.[17][18] The common ancestor of hippos and whales branched off from Ruminantia and the rest of the even-toed ungulates(HP Pavilion dv6-3115sa battery); the cetacean and hippo lineages split soon afterwards.

The most recent theory of the origins of Hippopotamidae suggests that hippos and whales shared a common semi-aquatic ancestor that branched off from other artiodactyls around 60 million years ago.[15][17] This hypothesized ancestral group likely split into two branches around 54 million years ago.[14] One branch would evolve into cetaceans(HP Pavilion dv6-3115tx battery), possibly beginning about 52 million years ago with the proto-whale Pakicetus and other early whale ancestors collectively known as Archaeoceti, which eventually underwent aquatic adaptation into the completely aquatic cetaceans.[19]

Hippopotamus madagascariensis skeleton with a modern hippopotamus skull.

The other branch became the anthracotheres, a large family of four-legged beasts, the earliest of whom in the late Eocene would have resembled skinny hippopotamuses with comparatively small and narrow heads(HP Pavilion dv6-3116sa battery). All branches of the anthracotheres, except that which evolved into Hippopotamidae, became extinct during the Pliocene without leaving any descendants.[17]

A rough evolutionary lineage can be traced from Eocene and Oligocene species: Anthracotherium and Elomeryx to the Miocene Merycopotamus and Libycosaurus and the very latest anthracotheres in the Pliocene.[20] Merycopotamus, Libycosaurus and all hippopotamids can be considered to form a clade, with Libycosaurus being more closely related to hippos(HP Pavilion dv6-3116tx battery). Their common ancestor would have lived in the Miocene, about 20 million years ago.

Hippopotamids are therefore deeply nested within the family Anthracotheriidae. The Hippopotamidae are believed to have evolved in Africa; the oldest known hippopotamid is the genus Kenyapotamus which lived in Africa from 16 to 8 million years ago. While hippopotamid species spread across Asia and Europe(HP Pavilion dv6-3117sa battery), no hippopotamuses have ever been discovered in the Americas, although various anthracothere genera emigrated into North America during the early Oligocene. From 7.5 to 1.8 million years ago an ancestor to the modern hippopotamus, Archaeopotamus, lived in Africa and the Middle East.[21]

While the fossil record of hippos is still poorly understood, the two modern genera, Hippopotamus and Choeropsis (sometimes Hexaprotodon) (HP Pavilion dv6-3118sa battery), may have diverged as far back as 8 million years ago. Taxonomists disagree whether or not the modern Pygmy Hippopotamus is a member of Hexaprotodon —an apparently paraphyletic genus also embracing many extinct Asian hippopotamuses that is more closely related to Hippopotamus, or Choeropsis —an older and basal genus(HP Pavilion dv6-3119sa battery).

Extinct species

Three species of Malagasy Hippopotamus became extinct during the Holocene on Madagascar, one of them within the past 1,000 years. The Malagasy Hippos were smaller than the modern hippopotamus, likely through the process of insular dwarfism.[22] There is fossil evidence that many Malagasy Hippos were hunted by humans, a likely factor in their eventual extinction. (HP Pavilion dv6-3120sa battery)Isolated members of Malagasy Hippopotamus may have survived in remote pockets; in 1976, villagers described a living animal called the Kilopilopitsofy, which may have been a Malagasy Hippopotamus.[23]

Two species of Hippopotamus, the European Hippopotamus (H. antiquus) and H. gorgops ranged throughout continental Europe and the British Isles. Both species became extinct before the last glaciation. Ancestors of European Hippos found their way to many islands of the Mediterranean during the Pleistocene. (HP Pavilion dv6-3121sa battery) Both species were larger than the modern hippopotamus, averaging about 1 meter (3.3 feet) longer.

The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands including Crete (H. creutzburgi), Cyprus (H. minor), Malta (H. melitensis) and Sicily (H. pentlandi). Of these, the Cyprus Dwarf Hippopotamus, survived until the end of the Pleistocene or early Holocene(HP Pavilion dv6-3122sa battery). Evidence from an archaeological site Aetokremnos, continues to cause debate on whether or not the species was encountered, and was driven to extinction, by man.[25][24]

Description

A hippo's skull, showing the large canine teeth used for fighting

Hippopotamuses are among the largest living mammals; only elephants and some rhinoceroses and whales are heavier. They can live in the water or on land. Their specific gravity allows them to sink and walk or run along the bottom of a river(HP Pavilion dv6-3123sa battery). Hippos are considered megafauna, but unlike all other African megafauna, hippos have adapted for a semi-aquatic life in freshwater lakes and rivers.[11]:3

Because of their enormous size, hippopotamuses are difficult to weigh in the wild. Most estimates of the weight come from culling operations that were carried out in the 1960s. The average weights for adult males ranged between 1,500–1,800 kg (3,300–4,000 lb) (HP Pavilion dv6-3125sa battery). Females are smaller than their male counterparts, with average weights measuring between 1,300–1,500 kg (2,900–3,300 lb).[11]:12 Older males can get much larger, reaching at least 3,200 kg (7,100 lb) and occasionally weighing 4,500 kg (9,900 lb).[26][27] Male hippos appear to continue growing throughout their lives; females reach a maximum weight at around age 25. (HP Pavilion dv6-3127sa battery)

Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder.[29][30] The range of hippopotamus sizes overlaps with the range of the White Rhinoceros; use of different metrics makes it unclear which is the largest land animal after elephants. Even though they are bulky animals, hippopotamuses can run faster than a human on land(HP Pavilion dv6-3130sa battery). Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters. Despite being semi-aquatic and having webbed feet, an adult hippo is not a particularly good swimmer nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps from the bottom. (HP Pavilion dv6-3131sa battery)

An open mouth signals that the hippo feels threatened.

The eyes, ears, and nostrils of hippos are placed high on the roof of the skull. This allows them to be in the water with most of their body submerged in the waters and mud of tropical rivers to stay cool and prevent sunburn. Their skeletal structure is graviportal, adapted to carrying the animals' enormous weight. Hippopotamuses have small legs (relative to other megafauna) (HP Pavilion dv6-3140sa battery)because the water in which they live reduces the weight burden. Unlike most other semi-aquatic animals, the hippopotamus has very little hair.[8]:260 The skin is 6 in (15 cm) thick,[31] providing it great protection against conspecifics and predators. The animals's upper parts are purplish-gray to blue-black while the under parts and areas around the eyes and ears can be brownish-pink. (HP Pavilion dv6-3141sa battery)

The hippo's jaw is powered by a large masseter and a well developed digastric; the latter loops up behind the former to the hyoid.[8]:259 The animal has a distinctive gape, which can reach 150°.[31] On the National Geographic Channel television program, "Dangerous Encounters with Brady Barr", Dr. Brady Barr measured the bite force of an adult female hippo at 8100 N (1821 lbf) (HP Pavilion dv6-3150sa battery); Barr also attempted to measure the bite pressure of an adult male hippo, but had to abandon the attempt due to the male's aggressiveness.[32] Hippopotamus teeth sharpen themselves as they grind together. The lower canines and lower incisors are enlarged, especially in males, and grow continuously. The incisors can reach 40 cm (16 in) while the canines reach up to 50 cm (20 in). (HP Pavilion dv6-3163eo battery)

Their skin secretes a natural sunscreen substance which is red-colored. The secretion is sometimes referred to as "blood sweat," but is neither blood nor sweat. This secretion is initially colorless and turns red-orange within minutes, eventually becoming brown. Two distinct pigments have been identified in the secretions, one red (hipposudoric acid) (HP Pavilion dv6-3180ea battery) and one orange (norhipposudoric acid). The two pigments are highly acidic compounds. Both pigments inhibit the growth of disease-causing bacteria; as well, the light absorption of both pigments peaks in the ultraviolet range, creating a sunscreen effect. All hippos, even those with different diets, secrete the pigments, so it does not appear that food is the source of the pigments. Instead, the animals may synthesize the pigments from precursors such as the amino acid tyrosine. (HP Pavilion dv6-3298ea battery)

A hippo's lifespan is typically 40–50 years.[8]:277 Donna the Hippo, 60, is the oldest living hippo in captivity. She lives at the Mesker Park Zoo in Evansville, Indiana, USA.[34][35] The oldest hippo ever recorded was called Tanga; she lived in Munich, Germany, and died in 1995 at the age of 61. (HP Pavilion dv6-3299ea battery)

Distribution

Hippopotamus amphibius was widespread in North Africa and Europe during the Eemian[37] and late Pleistocene until about 30,000 years ago. The species was common in Egypt's Nile region until historic times but has since been extirpated. Pliny the Elder writes that, in his time, the best location in Egypt for capturing this animal was in the Saite nome; (HP Pavilion dv6-3300 battery) the animal could still be found along the Damietta branch after the Arab Conquest in 639. Hippos are still found in the rivers and lakes of Uganda, Sudan, Somalia, Kenya, northern Democratic Republic of the Congo and Ethiopia, west through Ghana to Gambia, and also in Southern Africa (Botswana, Republic of South Africa, Zimbabwe, Zambia). A separate population exists in Tanzania and Mozambique(HP Pavilion dv6-3300sg battery).

Conservation status

The Hippopotamus Hunt (1617), by Peter Paul Rubens

Genetic evidence suggests that common hippos in Africa experienced a marked population expansion during or after the Pleistocene Epoch, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications as hippo populations across the continent are currently threatened by loss of access to fresh water. (HP Pavilion dv6-3350ef battery) Hippos are also subject to unregulated hunting and poaching. In May 2006 the hippopotamus was identified as a vulnerable species on the IUCN Red List drawn up by the World Conservation Union (IUCN), with an estimated population of between 125,000 and 150,000 hippos, a decline of between 7% and 20% since the IUCN's 1996 study. (HP Pavilion dv6-3350sf battery)

The hippo population declined most dramatically in the Democratic Republic of the Congo.[39] The population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid 1970s.[40] The decline is attributed to the disruptions caused by the Second Congo War.[40] The poachers are believed to be former Hutu rebels(HP Pavilion dv6-3351ef battery), poorly paid Congolese soldiers, and local militia groups.[40] Reasons for poaching include the belief that hippos are harmful to society, and also for money.[41] The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track.

[edit]Invasive potential

In the late 1980s, Pablo Escobar kept four hippos in a private menagerie at his residence in Hacienda Napoles, 100 km east of Medellín, Colombia, after buying them in New Orleans(HP Pavilion dv6-3351sf battery). They were deemed too difficult to seize and move after Escobar's fall, and hence left on the untended estate. By 2007, the animals had multiplied to 16 and had taken to roaming the area for food in the nearby Magdalena River.[42] In 2009, two adults and one calf escaped the herd, and after attacking humans and killing cattle, one of the adults (called "Pepe") (HP Pavilion dv6-3355ef battery)was killed by hunters under authorization of the local authorities.[43][44] It is unknown what kind of effects the presence of hippos might have on the ecosystem in Colombia. According to experts interviewed by W Radio Colombia, the animals could survive in the Colombian jungles. It is believed that the lack of control from the Colombian government, which is not used to dealing with this species, could result in human fatalities(HP Pavilion dv6-3355sf battery).

Behavior

A bull hippo out of water during daylight

Hippos spend most of their days wallowing in the water or the mud, with the other members of their pod. The water serves to keep their body temperature down, and to keep their skin from drying out. With the exception of eating, most of hippopotamuses' lives —from childbirth, fighting with other hippos, to reproduction— occur in the water(HP Pavilion dv6-3362ef battery).

Hippos leave the water at dusk and travel inland, sometimes up to 8 kilometers (5 mi), to graze on short grass, their main source of food. They spend four to five hours grazing and can consume 68 kilograms (150 lb) of grass each night.[45] Like almost any herbivore, they will consume many other plants if presented with them(HP Pavilion dv6-3362sf battery), but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants.[46] Hippos have (rarely) been filmed eating carrion, usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.[47] The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is likely caused by aberrant behavior or nutritional stress. HP Pavilion dv6-6000 battery 

The diet of hippos consists mostly of terrestrial grasses, even though they spend most of their time in the water. Most of their defecation occurs in the water, creating allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function.[46] Because of their size and their habit of taking the same paths to feedHP Pavilion dv6-6000eg battery, hippos can have a significant impact on the land they walk across, both by keeping the land clear of vegetation and depressing the ground. Over prolonged periods hippos can divert the paths of swamps and channels.[48]

Adult hippos move at speeds up to 8 km/h (5 mph) in water. Adult hippos typically resurface to breathe every three to five minutes. The young have to breathe every two to three minutes. HP Pavilion dv6-6001ea batteryThe process of surfacing and breathing is automatic, and even a hippo sleeping underwater will rise and breathe without waking. A hippo closes its nostrils when it submerges.

As with fish and turtles on a coral reef, hippo occasionally visit cleaning stations and signal by wide-open mouth their readiness for being cleaned of parasites by certain species of fish. This situation is an example of mutualism in which the hippo benefits from the cleansing while the fish receive food. HP Pavilion dv6-6001eg battery

[edit]Social life

A hippopotamus pod

Studying the interaction of male and female hippopotamuses has long been complicated by the fact that hippos are not sexually dimorphic and thus females and young males are almost indistinguishable in the field.[50] Although hippos like to lie close to each other, they do not seem to form social bonds except between mothers and daughters, and are not social animals. The reason they huddle close together is unknown. HP Pavilion dv6-6001sg battery

Hippopotamuses are territorial only in water, where a bull presides over a small stretch of river, on average 250 meters in length, and containing ten females. The largest pods can contain over 100 hippos.[11]:50 Other bachelors are allowed in a bull's stretch, as long as they behave submissively toward the bull. The territories of hippos exist to establish mating rights. Within the pods, the hippos tend to segregate by genderHP Pavilion dv6-6002eg battery. Bachelors will lounge near other bachelors, females with other females, and the bull on his own. When hippos emerge from the water to graze, they do so individually.[11]:4

Hippopotamuses appear to communicate verbally, through grunts and bellows, and it is thought that they may practice echolocation, but the purpose of these vocalizations is currently unknown. Hippos have the unique ability to hold their head partially above the water and send out a cry that travels through both water and air; hippos above and under water will respond. HP Pavilion dv6-6002sg battery

Reproduction

Hippos are born underwater.

Female hippos reach sexual maturity at five to six years of age and have a gestation period of 8 months. A study of endocrine systems revealed that female hippopotamuses may begin puberty as early as 3 or 4 years of age.[52] Males reach maturity at around 7.5 years.

A study of hippopotamus reproductive behavior in Uganda showed that peak conceptions occurred during the end of the wet season in the summerHP Pavilion dv6-6003eg battery, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's estrous cycle; as with most large mammals, male hippopotamus spermatozoa is active year round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season.[11]:60–61 After becoming pregnant, a female hippopotamus will typically not begin ovulation again for 17 months. HP Pavilion dv6-6004sa battery

Mating occurs in the water with the female submerged for most of the encounter,[11]:63 her head emerging periodically to draw breath. Hippos are one of the few mammals that give birth under water, along with Cetaceans and Sirenians (manatees and dugongs). Baby hippos are born underwater at a weight between 25 and 45 kg (60–110 lb) and an average length of around 127 cm (50 in) HP Pavilion dv6-6005ea battery and must swim to the surface to take their first breath. A mother typically gives birth to only one hippo, although twins also occur. The young often rest on their mothers' backs when in water that is too deep for them, and they swim underwater to suckle. They also will suckle on land when the mother leaves the water. Weaning starts between six and eight months after birth and most calves are fully weaned after a yearHP Pavilion dv6-6005eg battery.

Like many other large mammals, hippos are described as K-strategists, in this case typically producing just one large, well-developed infant every couple of years (rather than large numbers of small, poorly developed young several times per year as is common among small mammals such as rodents) HP Pavilion dv6-6005sg battery.

Aggression

Male hippos fighting

Hippopotamuses are by nature very aggressive animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions and spotted hyenas are known to prey on young hippos.[54] Hippos are very aggressive towards humansHP Pavilion dv6-6006ea battery, whom they commonly attack whether in boats or on land with no apparent provocation.[55] They are widely considered to be one of the most dangerous large animals in Africa.[56][57]

To mark territory, hippos spin their tails while defecating to distribute their excrement over a greater area.[58] Likely for the same reason, hippos are retromingent – that is, they urinate backwards. HP Pavilion dv6-6007sg battery

When in combat, male hippos use their incisors to parry each others attacks, and their lower canines to inflict damage.[8] Hippos rarely kill each other, even in territorial challenges. Usually a territorial bull and a challenging bachelor will stop fighting when it is clear that one hippo is stronger. When hippos become overpopulated, or when a habitat starts to shrinkHP Pavilion dv6-6007tx battery, bulls will sometimes attempt to kill infants, but this behavior is not common under normal conditions.[53] Some incidents of hippo cannibalism have been documented, but it is believed to be the behavior of distressed or sick hippos, and not healthy behavior.[11]:82–83

Hippos and humans

A faience sculpture, from the New Kingdom of Egypt, 18th/19th dynasty, c. 1500–1300 BC, when hippos were still widespread along the NileHP Pavilion dv6-6008eg battery

Obaysch lounging at the London Zoo in 1852

The earliest evidence of human interaction with hippos comes from butchery cut marks upon hippo bones at Bouri Formation dated around 160,000 years ago.[60] Later rock paintings and engravings showing hippos being hunted have been found in the mountains of the central Sahara dated 4,000–5,000 years ago near Djanet in the Tassili n'Ajjer MountainsHP Pavilion dv6-6008sa battery. Hippos were also well-known to the ancient Egyptians, where the hippo was recognized as a ferocious denizen of the Nile.

The Hippopotamus was also known to the Greeks and Romans. The Greek historian Herodotus described the hippopotamus in The Histories (written circa 440 BC) and the Roman Historian Pliny the Elder wrote about the hippopotamus in his encyclopedia Naturalis Historia (written circa 77 AD). HP Pavilion dv6-6008tx batteryHippopotamus was one of the many exotic animals brought to fight gladiators in Rome by the emperor Philip I the Arab to commemorate Rome's 1000 years anniversary in 248 AD. Silver coins with hippo's image were minted that year.

Zulu warriors preferred to be as brave as a hippopotamus, since even lions were not considered as brave. "In 1888, Captain Baden-Powell was part of a column searching for the Zulu chief DinizuluHP Pavilion dv6-6011tu battery, who was leading the Usutu people in revolt against the British colonists. The column was joined by John Dunn, a white Zulu chief, who led an impi (army) of 2000 Zulu warriors to join the British." [62]

The words of the Zulu anthem sounded like this:

"Een-gonyama Gonyama! "Invooboo! Yah-bo! Yah-bo! Invooboo!"

"John Dunn was at the head of his impi. [Baden Powell] asked him to translate the Zulu anthem his men had been singing. Dunn laughed and replied: "He is a lion. Yes, he is better than a lion—he is a hippopotamus." HP Pavilion dv6-6012tu battery

[edit]Hippos in zoos

Hippopotamuses have long been popular zoo animals. The first zoo hippo in modern history was Obaysch who arrived at the London Zoo on May 25, 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the Hippopotamus Polka.[64] Hippos have remained popular zoo animals since Obaysch, and generally breed well in captivityHP Pavilion dv6-6013cl battery. Their birth rates are lower than in the wild, but this is attributed to zoos' not wanting to breed as many hippos as possible, since hippos are large and relatively expensive animals to maintain.[11]:129[64]

Like many zoo animals, hippos were traditionally displayed in concrete exhibits. In the case of hippos, they usually had a pool of water and patch of grass. In the 1980s, zoo designers increasingly designed exhibits that reflected the animals' native habitatsHP Pavilion dv6-6013tu battery. The best known of these, the Toledo Zoo Hippoquarium, features a 360,000 gallon pool for hippos.[65] In 1987, researchers were able to tape, for the first time, an underwater birth (as in the wild) at the Toledo Zoo. The exhibit was so popular that the hippos became the logo of the Toledo Zoo.[66]

Cultural depictions

The cover of the Hippopotamus Polka. The unlikely portrayal of dancing hippos was echoed in Disney's FantasiaHP Pavilion dv6-6022eg battery.

A red hippo represented the Ancient Egyptian god Set; the thigh is the 'phallic leg of set' symbolic of virility. Set's consort Tawaret was also seen as part hippo.[67] The hippopotamus-headed Tawaret was a goddess of protection in pregnancy and childbirth, because ancient Egyptians recognized the protective nature of a female hippopotamus toward her young. HP Pavilion dv6-6023tx battery The Behemoth from the Book of Job, 40:15–24 is also thought to be based on a hippo.[69] The Ijo people wore masks of aquatic animals like the hippo when practicing their water spirit cults.[70]

Hippos have been the subjects of various African folktales. According to a Bushmen story; when the Creator assigned each animal their place in nature, the hippos wanted to live in the water, but were refused out of fear that they might eat all the fishHP Pavilion dv6-6024tx battery. After begging and pleading, the hippos were finally allowed to live in the water on the conditions that they would eat grass instead of fish and would fling their dung so he can inspect it for fish bones. [71] In a Ndebele tale, the hippo originally had long, beautiful hair but was set on fire by a jealous hare and had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water. HP Pavilion dv6-6025tx battery

Ever since Obaysch inspired the Hippopotamus Polka, hippos have been popular animals in Western culture for their rotund appearance that many consider comical.[64] Stories of hippos like Huberta who became a celebrity in South Africa in the 1930s for trekking across the country;[72] or the tale of Owen and Mzee, a hippo and tortoise who developed an intimate bond; have amused people who have bought hippo books, merchandiseHP Pavilion dv6-6026tx battery, and many a stuffed hippo toy.[73][74] Hippos were mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953.[75] They also feature in the songs "The Hippopotamus" and "Hippo Encore" by Flanders and Swann, with the famous refrain Mud, Mud, Glorious Mud. They even inspired a popular board game, Hungry Hungry Hippos. HP Pavilion dv6-6027tx battery

Hippos have also been popular cartoon characters, where their rotund frame is used for humorous effect. The Disney film Fantasia featured a ballerina hippopotamus dancing to the opera, La Gioconda.[39] Other cartoon hippos have included Hanna-Barbera's Peter Potamus, the book and TV series George and Martha, Flavio and Marita on the AnimaniacsHP Pavilion dv6-6029tx battery, Pat of the French duo Pat et Stanley, The Backyardigan's Tasha, and Gloria and Moto-Moto from the Madagascar franchise. A Sesame Street cartoon from the early 1970s features a hippo who lives in the country and likes it quiet, while being disturbed when the mouse who likes it loud moves in with her.

The hippopotamus characters "Happy Hippos" were created in 1988 by the French designer Andre Roche [78] based in MunichHP Pavilion dv6-6042sf battery, to be hidden in the "Kinder Surprise egg" of the Italian chocolate company Ferrero SpA. These characters were not placid like real hippos but rather cute and lively, and had such a success that they reappeared several times in different products of this company in the following years, increasing their popularity worldwide each timeHP Pavilion dv6-6051sf battery. The Nintendo Company published in the years 2001 and 2007 Game Boy adventures of them. In the game of chess, the hippopotamus lends its name to the Hippopotamus Defense, an opening system, which is generally considered weak.The River Horse is a popular outdoor sculpture at George Washington University, Washington, D.CHP Pavilion dv6-6051xx battery.

Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world. There are eight different genera in the family classified as rabbits, including the European rabbit (Oryctolagus cuniculus), cottontail rabbits (genus Sylvilagus; 13 species), and the Amami rabbit (Pentalagus furnessi, an endangered species on Amami Ōshima, Japan) (Dell 1691P battery). There are many other species of rabbit, and these, along with pikas and hares, make up the order Lagomorpha. The male is called a buck and the female is a doe; a young rabbit is a kitten or kit.

Habitat and range

Outdoor entrance to a rabbit burrow

Rabbit habitats include meadows, woods, forests, grasslands, deserts and wetlands.[1] Rabbits live in groups, and the best known species, the European rabbit, lives in underground burrows, or rabbit holes. A group of burrows is called a warren(Dell 310-6321 battery).

More than half the world's rabbit population resides in North America. They are also native to southwestern Europe, Southeast Asia, Sumatra, some islands of Japan, and in parts of Africa and South America. They are not naturally found in most of Eurasia, where a number of species of hares are present. Rabbits first entered South America relatively recently(Dell 312-0068 battery), as part of the Great American Interchange. Much of the continent has just one species of rabbit, the tapeti, while most of South America's southern cone is without rabbits.

The European rabbit has been introduced to many places around the world.

Morphology and ecology

The rabbit's long ears, which can be more than 10 cm (4 in) long, are probably an adaptation for detecting predators. They have large, powerful hind legs(Dell 312-0078 battery). The two front paws have 5 toes, the extra called the dewclaw. The hind feet have 4 toes.[3] They are plantigrade animals while at rest; however, they move around on their toes while running, assuming a more digitigrade form. Wild rabbits do not differ much in their body proportions or stance, with full(Dell 312-0079 battery), egg-shaped bodies. Their size can range anywhere from 20 cm (8 in) in length and 0.4 kg in weight to 50 cm (20 in) and more than 2 kg. The fur is most commonly long and soft, with colors such as shades of brown, gray, and buff. The tail is a little plume of brownish fur (white on top for cottontails).

Because the rabbit's epiglottis is engaged over the soft palate except when swallowing, the rabbit is an obligate nasal breather(Dell 312-0305 battery). Rabbits have two sets of incisor teeth, one behind the other. This way they can be distinguished from rodents, with which they are often confused.[4] Carl Linnaeus originally grouped rabbits and rodents under the class Glires; later, they were separated as the predominant opinion was that many of their similarities were a result of convergent evolution(Dell 312-0326 battery). However, recent DNA analysis and the discovery of a common ancestor has supported the view that they share a common lineage, and thus rabbits and rodents are now often referred to together as members of the superclass Glires.

Rabbits are hindgut digesters. This means that most of their digestion takes place in their large intestine and cecum(Dell 312-0518 battery). In rabbits the cecum is about 10 times bigger than the stomach and it along with the large intestine makes up roughly 40% of the rabbit's digestive tract.[6] The unique musculature of the cecum allows the intestinal tract of the rabbit to separate fibrous material from more digestible material; the fibrous material is passed as feces, while the more nutritious material is encased in a mucous lining as a cecotrope(Dell 312-0566 battery). Cecotropes, sometimes called "night feces", are high in minerals, vitamins and proteins that are necessary to the rabbit's health. Rabbits eat these to meet their nutritional requirements; the mucous coating allows the nutrients to pass through the acidic stomach for digestion in the intestines. This process allows rabbits to extract the necessary nutrients from their food(Dell 312-0585 battery).

Rabbits are prey animals and are therefore constantly aware of their surroundings. For instances, in Mediterranean Europe, rabbits are the main prey of red foxes, badgers, and Iberian lynxes.[8] If confronted by a potential threat, a rabbit may freeze and observe then warn others in the warren with powerful thumps on the ground. Rabbits have a remarkably wide field of vision(Dell 312-0831 battery), and a good deal of it is devoted to overhead scanning. They survive predation by burrowing, hopping away in a zig- zag motion, and, if captured, delivering powerful kicks with their hind legs. Their strong teeth allow them to eat and to bite in order to escape a struggle.

Sleep

Further information: Sleep (non-human)

The average sleep time of a captive rabbit is said to be 8.4 hours.

Reproduction

A litter of rabbit kits (baby rabbits)

A nest containing baby rabbits

Rabbits have a very rapid reproductive rate. The breeding season for most rabbits lasts 9 months, from February to October(Dell BAT30WL battery). In Australia and New Zealand breeding season is late July to late January. Normal gestation is about 30 days. The average size of the litter varies but is usually between 4 and 12 babies, with larger breeds having larger litters. A kit (baby rabbit) can be weaned at about 4 to 5 weeks of age. This means in one season a single female rabbit can produce as many as 800 children, grandchildren, and great-grandchildren(Dell D6400 battery). A doe is ready to breed at about 6 months of age, and a buck at about 7 months. Courtship and mating are very brief, lasting only 30 to 40 seconds. Courtship behavior involves licking, sniffing, and following the doe. Spraying urine is also a common sexual behavior. Female rabbits are reflex ovulators. The female rabbit also may or may not lose clumps of hair during the gestation period(Dell HF674 battery).

Ovulation begins 10 hours after mating. After mating, the female makes a nest or burrow, and lines the nest with fur from her dewlap, flanks and belly. This behavior also exposes the nipples enabling her to better nurse the kits. Kits are altricial, which means they are born blind, naked, and helpless. Passive immunity (immunity acquired by transfer of antibodies or sensitized lymphocytes from another animal) is acquired by kits prior to birth via placental transfer(Dell N3010 battery).

Due to the nutritious nature of rabbit milk kits only need to be nursed for a few minutes once or twice a day.[12] At 10 to 11 days after birth the baby rabbits' eyes open and they start eating on their own at around 14 days old. Although born naked, they form a soft baby coat of hair within a few days. At the age of 5 to 6 weeks the soft baby coat is replaced with a pre-adult coat(Dell Inspiron N4010 battery). At about 6 to 8 months of age (the age that rabbits are fully grown) this intermediate coat is replaced by the final adult coat, which is shed twice a year thereafter.

The expected rabbit lifespan is about 9–12 years; the world's longest-lived was 18 years.[15]

Diet and eating habits

Rabbits are herbivores that feed by grazing on grass, forbs, and leafy weeds. In consequence, their diet contains large amounts of cellulose, which is hard to digest. Rabbits solve this problem by passing two distinct types of feces(Dell INSPIRON 1100 battery): hard droppings and soft black viscous pellets, the latter of which are immediately eaten. Rabbits reingest their own droppings (rather than chewing the cud as do cows and many other herbivores) to digest their food further and extract sufficient nutrients.[16]

Rabbits graze heavily and rapidly for roughly the first half hour of a grazing period (usually in the late afternoon), followed by about half an hour of more selective feeding(Dell Inspiron 1200 battery). In this time, the rabbit will also excrete many hard fecal pellets, being waste pellets that will not be reingested. If the environment is relatively non-threatening, the rabbit will remain outdoors for many hours, grazing at intervals. While out of the burrow, the rabbit will occasionally reingest its soft, partially digested pellets; this is rarely observed, since the pellets are reingested as they are produced(Dell Inspiron 1420 battery). Reingestion is most common within the burrow between 8 o'clock in the morning and 5 o'clock in the evening, being carried out intermittently within that period.

Hard pellets are made up of hay-like fragments of plant cuticle and stalk, being the final waste product after redigestion of soft pellets. These are only released outside the burrow and are not reingested. Soft pellets are usually produced several hours after grazing, after the hard pellets have all been excreted. They are made up of micro-organisms and undigested plant cell walls(Dell Inspiron 1464 battery).

The chewed plant material collects in the large cecum, a secondary chamber between the large and small intestine containing large quantities of symbiotic bacteria that help with the digestion of cellulose and also produce certain B vitamins. The pellets are about 56% bacteria by dry weight, largely accounting for the pellets being 24.4% protein on average(Dell Inspiron 1564 battery). These pellets remain intact for up to six hours in the stomach; the bacteria within continue to digest the plant carbohydrates. The soft feces form here and contain up to five times the vitamins of hard feces. After being excreted, they are eaten whole by the rabbit and redigested in a special part of the stomach. This double-digestion process enables rabbits to use nutrients that they may have missed during the first passage through the gut(Dell Inspiron 1764 battery), as well as the nutrients formed by the microbial activity and thus ensures that maximum nutrition is derived from the food they eat.[2] This process serves the same purpose within the rabbit as rumination does in cattle and sheep.[17]

Rabbits are incapable of vomiting.[18]

Rabbit diseases

For a more comprehensive list, see Category:Rabbit diseases.

Some rabbits may have rabies.

Differences from hares

Main article: Hare

The most obvious difference between rabbits and hares is how their kits are born. Rabbits are altricial, having young that are born blind and hairless. In contrast, hares are born with hair and are able to see (precocial) (Dell Inspiron 1520 battery). All rabbits except cottontail rabbits live underground in burrows or warrens, while hares live in simple nests above the ground (as do cottontail rabbits), and usually do not live in groups. Hares are generally larger than rabbits, with longer ears, larger and longer hind legs and have black markings on their fur. Hares have not been domesticated, while European rabbits are both raised for meat and kept as pets(Dell Inspiron 1521 battery).

As pets

See also: House rabbit and Domestic rabbit

European Rabbit (Oryctolagus cuniculus)

Domestic rabbits can be kept as pets in a back yard hutch or indoors in a cage or house trained to have free roam. Rabbits kept indoors are often referred to as house rabbits. House rabbits typically have an indoor pen or cage and a rabbit-safe place to run and exercise, such as an exercise pen, living room or family room(Dell inspiron 1525 battery). Rabbits can be trained to use a litter box and some can learn to come when called. Domestic rabbits that do not live indoors can also serve as companions for their owners, typically living in a protected hutch outdoors. Some pet rabbits live in outside hutches during the day for the benefit of fresh air and natural daylight and are brought inside at night(Dell inspiron 1526 battery).

Whether indoor or outdoor, pet rabbits' pens are often equipped with enrichment activities such as shelves, tunnels, balls, and other toys. Pet rabbits are often provided additional space in which to get exercise, simulating the open space a rabbit would traverse in the wild. Exercise pens or lawn pens are often used to provide a safe place for rabbits to run(Dell Inspiron 1720 battery).

A pet rabbit's diet typically consists of unlimited timothy-grass or other hay, a small amount of pellets, and a fair quantity of fresh vegetables and need unrestricted access to fresh clean water. Rabbits are social animals. Rabbits as pets can find their companionship with a variety of creatures, including humans, other rabbits, birds, chinchillas, guinea pigs(Dell Inspiron 2000 battery), and sometimes even cats and dogs (however they require supervision when with dogs and cats, as they might be preyed upon or attacked by these animals). Rabbits can make good pets for younger children when proper parental supervision is provided. As prey animals, rabbits are alert, timid creatures that startle fairly easily. They have fragile bones, especially in their backs, that require support on the belly and bottom when picked up(Dell INSPIRON 2600 battery). Older children and teenagers usually have the maturity required to care for a rabbit.

As food and clothing

See also: Domestic rabbit

Rabbit meat sold commercially

Tanned rabbit pelt; rabbit pelt is prized for its softness.

An Australian 'Rabbiter' circa 1900

An old wooden cart, piled with rabbit skins, in New South Wales, Australia

Leporids such as European rabbits and hares are a food meat in Europe, South America, North America, some parts of the Middle East.

Rabbit is still sold in UK butchers and markets, and some supermarkets sell frozen rabbit meat. Additionally, some have begun selling fresh rabbit meat alongside other types of game. At farmers markets and the famous Borough Market in London(Dell INSPIRON 3800 battery), rabbits will be displayed dead and hanging unbutchered in the traditional style next to braces of pheasant and other small game. Rabbit meat was once commonly sold in Sydney, Australia, the sellers of which giving the name to the rugby league team the South Sydney Rabbitohs, but quickly became unpopular after the disease myxomatosis was introduced in an attempt to wipe out the feral rabbit population (see also Rabbits in Australia) (Dell INSPIRON 4000 battery). Rabbit meat is also commonly used in Moroccan cuisine, where it is cooked in a tajine with "raisins and grilled almonds added a few minutes before serving".[20]. Rabbit meat is unpopular in the Asia-Pacific.

When used for food, rabbits are both hunted and bred for meat. Snares or guns are usually employed when catching wild rabbits for food. In many regions, rabbits are also bred for meat, a practice called cuniculture(Dell Inspiron 5000 battery). Rabbits can then be killed by hitting the back of their heads, a practice from which the term rabbit punch is derived. Rabbit meat is a source of high quality protein.[21] It can be used in most ways chicken meat is used. In fact, well-known chef Mark Bittman says that domesticated rabbit tastes like chicken because both are blank palettes upon which any desired flavors can be layered. (Dell INSPIRON 500M battery)Rabbit meat is leaner than beef, pork, and chicken meat. Rabbit products are generally labeled in three ways, the first being Fryer. This is a young rabbit between 4.5 and 5 pounds and up to 9 weeks in age.[23] This type of meat is tender and fine grained. The next product is a Roaster; they are usually over 5 pounds and up to 8 months in age. The flesh is firm and coarse grained and less tender than a fryer(Dell INSPIRON 5100 battery). Then there are giblets which include the liver and heart. One of the most common types of rabbit to be bred for meat is New Zealand white rabbit.

There are several health issues associated with the use of rabbits for meat, one of which is tularemia or rabbit fever.[24] Another is so-called rabbit starvation, due most likely to deficiency of essential fatty acids in rabbit meat. Rabbits are a common food item of large pythons, such as Burmese pythons and reticulated pythons, both in the wild and in captivity(Dell INSPIRON 510M battery).

Rabbit pelts are sometimes used for clothing and accessories, such as scarves or hats. Angora rabbits are bred for their long, fine hair, which can be sheared and harvested like sheep wool. Rabbits are very good producers of manure; additionally, their urine, being high in nitrogen, makes lemon trees very productive. Their milk may also be of great medicinal or nutritional benefit due to its high protein content(Dell INSPIRON 6000 battery).

Environmental problems

See also: Rabbits in Australia

Rabbits have been a source of environmental problems when introduced into the wild by humans. As a result of their appetites, and the rate at which they breed, feral rabbit depredation can be problematic for agriculture. Gassing, barriers (fences), shooting, snaring, and ferreting have been used to control rabbit populations, but the most effective measures are diseases such as myxomatosis (myxo or mixi, colloquially) (Dell INSPIRON 600M battery) and calicivirus. In Europe, where rabbits are farmed on a large scale, they are protected against myxomatosis and calicivirus with a genetically modified virus. The virus was developed in Spain, and is beneficial to rabbit farmers. If it were to make its way into wild populations in areas such as Australia, it could create a population boom, as those diseases are the most serious threats to rabbit survival(Dell Inspiron 6400 battery). Rabbits in Australia and New Zealand are considered to be such a pest that land owners are legally obliged to control them.

When introduced into a new area, rabbits can overpopulate rapidly, becoming a nuisance, as on this university campus

European Rabbit in Shropshire, England, infected with myxomatosis, a disease caused by the Myxoma virus

In culture and literature

See also: List of fictional hares and rabbits

Rabbits are often used as a symbol of fertility or rebirth, and have long been associated with spring and Easter as the Easter Bunny. The species' role as a prey animal also lends itself as a symbol of innocence, another Easter connotation(Dell INSPIRON 7000 battery).

Additionally, rabbits are often used as symbols of playful sexuality, which also relates to the human perception of innocence, as well as its reputation as a prolific breeder.

Further information: Playboy Bunny

Folklore and mythology

The rabbit often appears in folklore as the trickster archetype, as he uses his cunning to outwit his enemies.

In Aztec mythology, a pantheon of four hundred rabbit gods known as Centzon Totochtin, led by Ometotchtli or Two Rabbit, represented fertility, parties, and drunkenness(Dell INSPIRON 700M battery).

In Central Africa, "Kalulu" the rabbit is widely known as a tricky character, getting the better of bargains.[citation needed]

In Chinese literature, rabbits accompany Chang'e on the Moon. Also associated with the Chinese New Year (or Lunar New Year), rabbits are also one of the twelve celestial animals in the Chinese Zodiac for the Chinese calendar. It is interesting to note that the Vietnamese lunar new year replaced the rabbit with a cat in their calendar, as rabbits did not inhabit Vietnam(Dell Inspiron 710m battery).

A rabbit's foot is carried as an amulet believed to bring good luck. This is found in many parts of the world, and with the earliest use being in Europe around 600 B.C.[28]

In Japanese tradition, rabbits live on the Moon where they make mochi, the popular snack of mashed sticky rice. This comes from interpreting the pattern of dark patches on the moon as a rabbit standing on tiptoes on the left pounding on an usu, a Japanese mortar (Dell INSPIRON 8200 battery).

In Jewish folklore, rabbits (shfanim שפנים) are associated with cowardice, a usage still current in contemporary Israeli spoken Hebrew (similar to English colloquial use of "chicken" to denote cowardice).

In Korean mythology, like in Japanese, presents rabbits living on the moon making rice cakes (Tteok in Korean) (Dell INSPIRON 8600 battery).

In Native American Ojibwe mythology, Nanabozho, or Great Rabbit, is an important deity related to the creation of the world.

A Vietnamese mythological story portrays the rabbit of innocence and youthfulness. The Gods of the myth are shown to be hunting and killing rabbits to show off their power.

On the Isle of Portland in Dorset, UK, the rabbit is said to be unlucky and speaking its name can cause upset with older residents(Dell INSPIRON 9100 battery). This is thought to date back to early times in the quarrying industry, where piles of extracted stone (not fit for sale) were built into tall rough walls (to save space) directly behind the working quarry face; the rabbit's natural tendency to burrow would weaken these "walls" and cause collapse, often resulting in injuries or even death(Dell INSPIRON 9200 battery). The name rabbit is often substituted with words such as “long ears” or “underground mutton”, so as not to have to say the actual word and bring bad luck to oneself. It is said that a public house (on the island) can be cleared of people by calling out the word rabbit and while this was very true in the past, it has gradually become more fable than fact over the past 50 years. See also Three hares(Dell INSPIRON 9300 battery).

Other fictional rabbits

Main article: List of fictional hares and rabbits

The rabbit as trickster appears in American popular culture; for example the Br'er Rabbit character from African-American folktales and Disney animation; and the Warner Bros. cartoon character Bugs Bunny.

Anthropomorphized rabbits have appeared in a host of works of film, literature, and technology, notably the White Rabbit and the March Hare in Lewis Carroll's Alice's Adventures in Wonderland(Dell Inspiron 9400 battery); in the popular novels Watership Down, by Richard Adams (which has also been made into a movie) and Rabbit Hill by Robert Lawson, as well as in Beatrix Potter's Peter Rabbit stories.

Urban legends

Main article: Rabbit test

It was commonly believed that pregnancy tests were based on the idea that a rabbit would die if injected with a pregnant woman's urine. This is not true. However, in the 1920s it was discovered that if the urine contained the hCG, a hormone found in the bodies of pregnant women(Dell Inspiron E1505 battery), the rabbit would display ovarian changes. The rabbit would then be killed to have its ovaries inspected, but the death of the rabbit was not the indicator of the results. Later revisions of the test allowed technicians to inspect the ovaries without killing the animal. A similar test involved injecting Xenopus frogs to make them lay eggs, but animal tests for pregnancy have been made obsolete by faster, cheaper, and simpler modern methods(Dell Inspiron E1705 battery).

Parrots, also known as psittacines ( /ˈsɪtəsaɪnz/), are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes,[4] found in most tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoidea ('true' parrots), the Cacatuoidea (cockatoos) and the Strigopoidea (New Zealand parrots). (Dell Inspiron Mini 9 battery) Parrots have a generally pantropical distribution with several species inhabiting temperate regions in the Southern Hemisphere as well. The greatest diversity of parrots is found in South America and Australasia.

Characteristic features of parrots include a strong, curved bill, an upright stance, strong legs, and clawed zygodactyl feet. Many parrots are vividly coloured, and some are multi-coloured(Dell Latitude D400 battery). The plumage of cockatoos ranges from mostly white to mostly black, with a mobile crest of feathers on the tops of their heads. Most parrots exhibit little or no sexual dimorphism. They form the most variably sized bird order in terms of length.

The most important components of most parrots' diets are seeds, nuts, fruit, buds and other plant material. A few species sometimes eat animals and carrion, while the lories and lorikeets are specialised for feeding on floral nectar and soft fruits(Dell STUDIO 1450 battery). Almost all parrots nest in tree hollows (or nest boxes in captivity), and lay white eggs from which hatch altricial (helpless) young.

Parrots, along with ravens, crows, jays and magpies, are among the most intelligent birds, and the ability of some species to imitate human voices enhances their popularity as pets. Trapping wild parrots for the pet trade, as well as hunting, habitat loss and competition from invasive species(Dell Vostro 1400 battery), has diminished wild populations, with parrots being subjected to more exploitation than any other group of birds.[6] Measures taken to conserve the habitats of some high-profile charismatic species have also protected many of the less charismatic species living in the same ecosystems(Dell Vostro 1500 battery).

Taxonomy

Origins and evolution

Blue-and-yellow Macaw eating a walnut held by a foot

Psittaciform diversity in South America and Australasia suggests that the order may have evolved in Gondwanaland, centred in Australasia.[8] The scarcity of parrots in the fossil record, however, presents difficulties in supporting the hypothesis.

A single 15 mm (0.6 in) fragment from a large lower bill (UCMP 143274), found in deposits from the Lance Creek Formation in Niobrara County, Wyoming(Dell XPS GEN 2 battery), had been thought to be the oldest parrot fossil and is presumed to have originated from the Late Cretaceous period, which makes it about 70 Ma (million years ago).[9] Other studies suggest that this fossil is not from a bird, but from a caenagnathid theropod or a non-avian dinosaur with a birdlike beak(Dell XPS M1210 battery).

It is now generally assumed that the Psittaciformes, or their common ancestors with several related bird orders, were present somewhere in the world around the Cretaceous–Paleogene extinction event (K-Pg extinction), some 65 Ma If so, they probably had not evolved their morphological autapomorphies yet, but were generalised arboreal birds(Dell XPS M1330 battery), roughly similar (though not necessarily closely related) to today's potoos or frogmouths (see also Palaeopsittacus below). Though these birds (Cypselomorphae) are a phylogenetically challenging group, they seem at least closer to the parrot ancestors than, for example, the modern aquatic birds (Aequornithes). The combined evidence supported the hypothesis of Psittaciformes being "near passerines"(Dell XPS 1340 battery), i.e. the mostly land-living birds that emerged in close proximity to the K-Pg extinction. Indeed, analysis of transposable element insertions observed in the genomes of passerines and parrots, but not in the genomes of other birds, provides strong evidence that parrots are the sister group of passerines, forming a clade Psittacopasserae, to the exclusion of the next closest group, the falcons. (Dell XPS M1530 battery)

Europe is the origin of the first presumed parrot fossils, which date from about 50 Ma. The climate there and then was tropical, consistent with the Paleocene-Eocene Thermal Maximum. Initially, a neoavian named Mopsitta tanta, uncovered in Denmark's Early Eocene Fur Formation and dated to 54 Ma, was assigned to the Psittaciformes(Dell XPS M170 battery); it was described from a single humerus.[13] However, the rather nondescript bone is not unequivocally psittaciform, and more recently it was pointed out that it may rather belong to a newly-discovered ibis of the genus Rhynchaeites, whose fossil legs were found in the same deposits.

The feathers of a Yellow-headed Amazon. The blue component of the green colouration is due to light scattering while the yellow is due to pigment(Dell XPS M1710 battery).

Fossils assignable to Psittaciformes (though not yet the present-day parrots) date from slightly later in the Eocene, starting around 50 Ma. Several fairly complete skeletons of parrot-like birds have been found in England and Germany.[14] Some uncertainty remains, but on the whole it seems more likely that these are not direct ancestors of the modern parrots(Dell XPS M1730 battery), but related lineages which evolved in the Northern Hemisphere and have since died out. These are probably not "missing links" between ancestral and modern parrots, but rather psittaciform lineages that evolved parallel to true parrots and cockatoos and had their own peculiar autapomorphies:

Psittacopes (Early/Middle Eocene of Geiseltal, Germany)—basal?

Serudaptus—pseudasturid or psittacid?

Pseudasturidae (Halcyornithidae may be correct name)

Pseudasturides – formerly Pseudastur

Vastanavidae(Dell XPS M2010 battery)

Vastanavis (Early Eocene of Vastan, India)

Quercypsittidae

Quercypsitta (Late Eocene)

The earliest records of modern parrots date to about 23–20 Ma and are also from Europe. Subsequently, the fossil record—again mainly from Europe—consists of bones clearly recognisable as belonging to parrots of modern type. The Southern Hemisphere does not have nearly as rich a fossil record for the period of interest as the Northern(Dell Latitude E5400 battery), and contains no known parrot-like remains earlier than the early to middle Miocene, around 20 Ma. At this point, however, is found the first unambiguous parrot fossil (as opposed to a parrot-like one), an upper jaw which is indistinguishable from that of modern cockatoos. A few modern genera are tentatively dated to a Miocene origin, but their unequivocal record stretches back only some 5 million years (see genus articles for more) (Dell Latitude E5500 battery).

Fossil skull of a presumed parrot relative from the Eocene Green River Formation in Wyoming.

The named fossil genera of parrots are probably all in the Psittacidae or close to its ancestry:

Archaeopsittacus (Late Oligocene/Early Miocene)

Xenopsitta (Early Miocene of Czechia)

Psittacidae gen. et spp. indet. (Bathans Early/Middle Miocene of Otago, New Zealand)—several species

Bavaripsitta (Middle Miocene of Steinberg, Germany)

Psittacidae gen. et sp. indet. (Middle Miocene of France)—erroneously placed in Pararallus dispar, includes "Psittacus" lartetianus(Dell Latitude E6400 battery)

Some Paleogene fossils are not unequivocally accepted to be of psittaciforms:

Palaeopsittacus (Early – Middle Eocene of NW Europe)—caprimulgiform (podargid?) or quercypsittid?

"Precursor" (Early Eocene)—part of this apparent chimera seems to be of a pseudasturid or psittacid

Pulchrapollia (Early Eocene)—includes "Primobucco" olsoni—psittaciform (pseudasturid or psittacid) (Dell Latitude E6500 battery)?

Molecular studies suggest that parrots evolved approximately 59 Ma (range 66–51 Ma) in Gondwanaland.[15] The three major clades of Neotropical parrots originated about 50 Ma (range 57–41 Ma).

[edit]Phylogeny

Phylogenetic relationship between the three parrot families based on the available literature

The Psittaciformes comprise three main lineages: Strigopoidea, Psittacoidea and Cacatuoidea(Dell Inspiron Mini 12 battery).

The Strigopoidea were considered part of the Psittacoidea, but recent studies place this group of New Zealand species at the base of the parrot tree next to the remaining members of the Psittacoidea as well as all members of the Cacatuoidea.

The Cacatuoidea are quite distinct, having a movable head crest, a different arrangement of the carotid arteries, a gall bladder, differences in the skull bones, and lack the Dyck texture feathers which(Dell XPS M140 battery), in the Psittacidae, scatters light in such a way as to produce the vibrant colours of so many parrots. Colourful feathers with high levels of psittacofulvin resist the feather-degrading bacterium Bacillus licheniformis better than white ones.[18]

Lorikeets were previously regarded as a third family, Loriidae,[19] but are now considered a tribe (Loriini) within the subfamily Lorinae. The two other tribes in the subfamily are the closely related fig parrots (two genera in the tribe Cyclopsittini) and Budgerigar (tribe Melopsittacini) (Dell XPS 13 battery).

Systematics

The following classification is based on the most recent proposal, which in turn is based on all the relevant recent findings.

Other lists

A list of all parrots sortable by common or binomial name, about 350 species.

Taxonomic list of Cacatuidae species, 21 species in 7 genera

Taxonomic list of true parrots which provides the sequence of Psittacidae genera and species following a traditional two-subfamily approach, as in the taxobox above, about 330 species(Dell XPS 16 battery).

List of Strigopidae

List of macaws

List of Amazon parrots

List of Aratinga parakeets

Morphology

Glossy Black Cockatoo showing the parrot's strong bill, clawed feet, and sideways positioned eyes

Extant species range in size from the Buff-faced Pygmy Parrot, at under 10 g (0.4 oz) in weight and 8 cm (3.1 in) in length, to the Hyacinth Macaw, at 1 m (3.3 ft) in length, and the Kakapo, at 4.0 kg (8.8 lb) in weight. Among the superfamilies(Dell XPS 1640 battery), the three extant Strigopoidea species are all large parrots, and the cockatoos tend to be large birds as well. The Psittacoidea parrots are far more variable, ranging the full spectrum of sizes shown by the family.

The most obvious physical characteristic is the strong, curved, broad bill. The upper mandible is prominent, curves downward, and comes to a point. It is not fused to the skull, which allows it to move independently(Dell XPS 1645 battery), and contributes to the tremendous biting pressure the birds are able to exert. The lower mandible is shorter, with a sharp, upward-facing cutting edge, which moves against the flat portion of the upper mandible in an anvil-like fashion. There are touch receptors along the inner edges of the kerantinised bill, which are collectively known as the 'bill tip organ', allowing for highly dextrous manipulations. Seed-eating parrots have a strong tongue (Dell XPS 1647 battery) (containing similar touch receptors to those in the bill tip organ), which helps to manipulate seeds or position nuts in the bill so that the mandibles can apply an appropriate cracking force. The head is large, with eyes positioned high and laterally in the skull, so the visual field of parrots are unlike any other birds. Without turning its head, a parrot can see from just below its bill tip, all above its head, and to quite far behind its head(Dell Latitude 131L battery). Parrots also have quite a wide frontal binocular field for a bird, although this is nowhere near as large as primate binocular visual fields.[24]

Parrots have strong zygodactyl feet with sharp, elongated claws, which are used for climbing and swinging. Most species are capable of using their feet to manipulate food and other objects with a high degree of dexterity, in a similar manner to a human using his hands. A study conducted with Australian parrots has demonstrated that they exhibit "handedness"(Dell Latitude C400 battery)—that is a distinct preference with regards to the foot used to pick up food, with adult parrots being almost exclusively "left-footed" or "right footed", and with the prevalence of each preference within the population varying from species to species.[25]

Cockatoo species have a mobile crest of feathers on the top of their heads which can be raised for display, and retracted. No other parrots can do so, but the Pacific lorikeets in the genera Vini and Phigys are able to ruffle the feathers of the crown and nape and the Red-fan Parrot (Dell Latitude C500 battery) (or Hawk-headed Parrot) has a prominent feather neck frill which can be raised and lowered at will. The predominant colour of plumage in parrots is green, though most species have some red or another colour in small quantities. Cockatoos are the main exception to this, having lost the green and blue plumage colours in their evolutionary history they are now predominately black or white with some red(Dell Latitude C510 battery), pink or yellow. Strong sexual dimorphism in plumage is not typical among parrots, with some notable exceptions, the most striking being the Eclectus Parrot.

Distribution and habitat

Most parrot species are tropical but a few species, like this Austral Parakeet, range deeply into temperate zones

Parrots are found on all tropical and subtropical continents including Australia and Oceania, South Asia, Southeast Asia, Central America, South America and Africa(Dell Latitude C540 battery). Some Caribbean and Pacific islands are home to endemic species. By far the greatest number of parrot species come from Australasia and South America. The lories and lorikeets range from Sulawesi and the Philippines in the north to Australia and across the Pacific as far as French Polynesia, with the greatest diversity being found in and around New Guinea. The subfamily Arinae encompasses all the Neotropical parrots(Dell Latitude C600 battery), including the Amazons, macaws and conures, and ranges from northern Mexico and the Bahamas to Tierra del Fuego in the southern tip of South America. The pygmy parrots, tribe Micropsittini, form a small genus restricted to New Guinea. The superfamily Strigopoidea contains three living species of aberrant parrots from New Zealand. The broad-tailed parrots, subfamily Platycercinae(Dell Latitude C610 battery), are restricted to Australia, New Zealand and the Pacific islands as far eastwards as Fiji. The true parrot superfamily, Psittacoidea, includes a range of species from Australia and New Guinea to South Asia and Africa. The centre of cockatoo biodiversity is Australia and New Guinea, although some species reach the Solomon Islands (and one formerly occurred in New Caledonia),[26] Wallacea and the Philippines(Dell Latitude C640 battery).

Several parrots inhabit the cool, temperate regions of South America and New Zealand. One, the Carolina Parakeet, lived in temperate North America, but was hunted to extinction in the early 20th century. Many parrots have been introduced to areas with temperate climates, and have established stable populations in parts of the United States (including New York City),[27] the United Kingdom,[28] Belgium[29] and Spain(Dell Latitude C800 battery).

Few parrots are wholly sedentary or fully migratory. Most fall somewhere between the two extremes, making poorly understood regional movements, with some adopting an entirely nomadic lifestyle.

Behaviour

There are numerous challenges in studying wild parrots, as they are difficult to catch and once caught they are difficult to mark. Most wild bird studies rely on banding or wing tagging, but parrots will chew off such attachments. (Dell Latitude C810 battery) Parrots also tend to range widely and consequently there are many gaps in knowledge of their behaviour. Some parrots have a strong, direct flight. Most species spend much of their time perched or climbing in tree canopies. They often use their bills for climbing by gripping or hooking on branches and other supports. On the ground parrots often walk with a rolling gait(Dell Latitude C840 battery).

Diet

A Yellow-tailed Black Cockatoo using its strong bill to search for grubs

The diet of parrots consists of seeds, fruit, nectar, pollen, buds, and sometimes arthropods and other animal prey. The most important of these for most true parrots and cockatoos are seeds; the evolution of the large and powerful bill can be explained primarily as an adaptation to opening and consuming seeds(Dell Latitude CPI battery). All true parrots except the Pesquet's Parrot employ the same method to obtain the seed from the husk; the seed is held between the mandibles and the lower mandible crushes the husk, whereupon the seed is rotated in the bill and the remaining husk is removed.[32] A foot is sometimes used to help holding large seeds in place. Parrots are seed predators rather than seed dispersers(Dell Latitude CPX battery); and in many cases where species are recorded as consuming fruit they are only eating the fruit to get at the seed. As seeds often have poisons to protect them, parrots are careful to remove seed coats and other fruit parts which are chemically well defended, prior to ingestion. Many species in the Americas, Africa, and Papua New Guinea consume clay which both releases minerals and absorbs toxic compounds from the gut. (Dell Latitude D410 battery)

Parrots at a clay lick in Ecuador.

The lories and lorikeets, hanging parrots and Swift Parrot are primarily nectar and pollen consumers, and have tongues with brush tips to collect this source of food, as well as some specialised gut adaptations to accommodate this diet.[34] Many other species also consume nectar as well when it becomes available(Dell Latitude D420 battery).

In addition to feeding on seeds and flowers, some parrot species will prey on animals, especially invertebrate larvae. Golden-winged Parakeets prey on water snails, and famously the Keas of New Zealand will kill juvenile petrels and even attack and indirectly kill adult sheep.[35] Another New Zealand parrot, the Antipodes Island Parakeet, enters the burrows of nesting Grey-backed Storm Petrels and kills the incubating adults. (Dell Latitude D430 battery) Some cockatoos and the Kākā will excavate branches and wood to obtain grubs; the bulk of the Yellow-tailed Black Cockatoo's diet is made up of insects.[37]

Breeding

Although there are a few exceptions, parrots are monogamous breeders which nest in cavities and hold no territories other than their nesting sites. The pair bonds of the parrots and cockatoos are strong and a pair will remain close even during the non-breeding season(Dell Latitude D500 battery), even if they join larger flocks. As with many birds, pair bond formation is preceded by courtship displays; these are relatively simple in the case of cockatoos. In Psittacidae parrots common breeding displays, usually undertaken by the male, include slow deliberate steps known as a "parade" or "stately walk" and the "eye-blaze", where the pupil of the eye constricts to reveal the edge of the iris. (Dell Latitude D505 battery) Allopreening is used by the pair to help maintain the bond. Cooperative breeding, where birds other than the breeding pair help the pair raise the young and is common in some bird families, is extremely rare in parrots, and has only unambiguously been demonstrated in the Golden Parakeet (which may also exhibit polyamorous, or group breeding, behaviour with multiple females contributing to the clutch). (Dell Latitude D510 battery)

The vast majority of parrots are, like this Blue-winged Parrotlet, cavity nesters.

Only the Monk Parakeet and five species of Agapornis lovebird build nests in trees,[40] and three Australian and New Zealand ground parrots nest on the ground. All other parrots and cockatoos nest in cavities, either tree hollows or cavities dug into cliffs, banks or the ground. The use of holes in cliffs is more common in the Americas. Many species will use termite nests(Dell Latitude D520 battery), possibly to reduce the conspicuousness of the nesting site or to create a favourable microclimate.[41] In most cases both parents will participate in the nest excavation. The length of the burrow varies with species, but is usually between 0.5–2 m (1.6–6.6 ft) in length. The nests of cockatoos are often lined with sticks, wood chips and other plant material. In the larger species of parrot and cockatoo the availability of nesting hollows may be limited(Dell Latitude D600 battery), leading to intense competition for them both within the species and between species, as well as with other bird families. The intensity of this competition can limit breeding success in some cases.[42][43] Some species are colonial, with the Burrowing Parrot nesting in colonies up to 70,000 strong.[44] Coloniality is not as common in parrots as might be expected, possibly because most species adopt old cavities rather than excavate their own. (Dell Latitude D610 battery)

The eggs of parrots are white. In most species the female undertakes all the incubation, although incubation is shared in cockatoos, the Blue Lorikeet, and the Vernal Hanging Parrot. The female remains in the nest for almost all of the incubation period and is fed both by the male and during short breaks. Incubation varies from 17 to 35 days(Dell Latitude D620 battery), with larger species having longer incubation periods. The newly born young are altricial, either lacking feathers or with sparse white down. The young spend anything from three weeks to four months in the nest, depending on species, and may receive parental care for several months thereafter. (Dell Latitude D630 battery)

As typical of K-selected species, the macaws and other larger parrot species have low reproductive rates. They require several years to reach maturity, produce one or very few young per year, and do not necessarily breed every year.

Intelligence and learning

Sun Conure demonstrating parrots' puzzle-solving skills

Studies with captive birds have given insight into which birds are the most intelligent. While parrots are able to mimic human speech, studies with the African Grey Parrot have shown that some are able to associate words with their meanings and form simple sentences (Dell Latitude D800 battery) (see Alex and N'kisi). Along with crows, ravens, and jays (family Corvidae), parrots are considered the most intelligent of birds. The brain-to body size ratio of psittacines and corvines is actually comparable to that of higher primates.[47] One argument against the supposed intelligent capabilities of bird species is that birds have a relatively small cerebral cortex, which is the part of the brain considered to be the main area of intelligence in other animals(Dell Latitude D810 battery). However, birds use a different part of the brain, the medio-rostral neostriatum / hyperstriatum ventrale, as the seat of their intelligence. Not surprisingly, research has shown that these species tend to have the largest hyperstriata, and Dr Harvey J. Karten, a neuroscientist at the University of California, San Diego, who studied bird physiology, has discovered that the lower part of the avian brain is functionally similar to that in humans(Dell Latitude D820 battery). Not only have parrots demonstrated intelligence through scientific testing of their language-using ability, but some species of parrot such as the Kea are also highly skilled at using tools and solving puzzles.[48]

Learning in early life is apparently important to all parrots, and much of that learning is social learning. Social interactions are often practised with siblings, and in several species creches are formed with several broods(Dell Latitude D830 battery), and these as well are important for learning social skills. Foraging behaviour is generally learnt from parents, and can be a very protracted affair. Supra-generalists and specialists are generally independent of their parents much quicker than partly specialised species which may have to learn skills over a long period of time as various resources become seasonally available(Dell Latitude 2100 battery). Play forms a large part of learning in parrots; it can be solitary, and related to motor skills, or social. Species may engage in play fights or wild flights to practice predator evasion. An absence of stimuli can retard the development of young birds, as demonstrated by a group of Vasa Parrots kept in tiny cages with domesticated chickens from the age of 3 months; at 9 months these birds still behaved in the same way as 3 month olds, but had adopted some chicken behaviour. (Dell Latitude 2110 battery) In a similar fashion captive birds in zoo collections or pets can, if deprived of stimuli, develop stereotyped behaviours and harmful behaviours like self plucking. Aviculturists working with parrots have identified the need for environmental enrichment to keep parrots stimulated.

Sound imitation and speech

Main article: Talking bird

See also: Animal language

Video of an Orange-winged Amazon saying "Hello" having been prompted by some people

Many parrots can imitate human speech or other sounds. A study by Irene Pepperberg suggested a high learning ability in an African Grey Parrot named Alex(Dell Latitude E4300 battery). Alex was trained to use words to identify objects, describe them, count them, and even answer complex questions such as "How many red squares?" with over 80% accuracy. N'kisi, another African grey, has been shown to have a vocabulary of approximately a thousand words, and has displayed an ability to invent as well as use words in context and in the correct tense(Dell Vostro 1310 battery).

Parrots do not have vocal cords, so sound is accomplished by expelling air across the mouth of the bifurcated trachea. Different sounds are produced by changing the depth and shape of trachea. African Grey Parrots of all subspecies are known for their superior ability to imitate sounds and human speech. This ability has made them prized as pets from ancient time to the present(Dell Vostro 1320 battery). In the Masnavi, a writing by Rumi of Persia, AD 1250, the author talks about an ancient method for training parrots to speak.

Although most parrot species are able to imitate, some of the Amazon parrots are generally regarded as the next-best imitators and speakers of the parrot world. The question of why birds imitate remains open, but those that do often score very high on tests designed to measure problem solving ability. Wild African Grey Parrots have been observed imitating other birds. (Dell Vostro 1510 battery)Most other wild parrots have not been observed imitating other species.

[edit]Cooperation

The journal Animal Cognition stated that some birds preferred to work alone, while others like to work together as with African Grey Parrots. With two parrots, they know the order of tasks or when they should do something together at once, but they have trouble to exchanging roles. With three parrots, one parrot usually prefers to cooperate with one of the other two, but all of them are cooperating to solve the task. (Dell Vostro 1520 battery)

Relationship with humans

Video of a Blue-fronted Amazon mimicking a human laughing

Humans and parrots have a complicated relationship. Economically they can be beneficial to communities as sources of income from the pet trade and are highly marketable tourism draws and symbols. But some species are also economically important pests, particularly some cockatoo species in Australia(Dell Vostro 2510 battery). Some parrots have also benefited from human changes to the environment in some instances, and have expanded their ranges alongside agricultural activity, but many species have declined as well.

There exist a number of careers and professions devoted to parrots. Zoos and aquariums employ keepers to care for and shape the behaviour of parrots. Some veterinarians who specialise in avian medicine will treat parrots exclusively(Dell Vostro 1014 battery). Biologists study parrot populations in the wild and help to conserve wild populations. Aviculturalists breed and sell parrots for the pet trade.

Tens of millions of parrots have been removed from the wild, and parrots have been traded in greater numbers and for far longer than any other group of wild animals.[51] Many parrot species are still threatened by this trade as well as habitat loss, predation by introduced species, and hunting for food or feathers. Some parrot species are agricultural pests, (Dell Inspiron 1410 battery) eating fruits, grains, and other crops, but parrots can also benefit economies through birdwatching based ecotourism.[53]

Pets

Pet Cuban Amazons in Cuba

Further information: Companion parrot

Parrots are popular as pets due to their sociable and affectionate nature, intelligence, bright colours, and ability to imitate human voices. The domesticated Budgerigar, a small parrot, is the most popular of all pet bird species. In 1992 the newspaper USA Today published that there were 11 million pet birds in the United States alone,[54] many of them parrots(Dell Vostro 1014N battery). Europeans kept birds matching the description of the Rose-ringed Parakeet (or called the ring-necked parrot), documented particularly in a first century account by Pliny the Elder.[55] As they have been prized for thousands of years for their beauty and ability to talk, they have also often been misunderstood. For example, author Wolfgang de Grahl discusses in his 1987 book The Grey Parrot that some importers allowed parrots to drink only coffee while they were being (Dell Vostro 1015 battery)shipped by boat considering pure water to be detrimental and believing that their actions would increase survival rates during shipping. (Nowadays it is commonly accepted that the caffeine in coffee is toxic to birds.)

Pet parrots may be kept in a cage or aviary; though generally, tame parrots should be allowed out regularly on a stand or gym. Depending on locality, parrots may be either wild caught or be captive bred, though in most areas without native parrots(Dell Inspiron 1088 battery), pet parrots are captive bred. Parrot species that are commonly kept as pets include conures, macaws, Amazons, cockatoos, African Greys, lovebirds, cockatiels, Budgerigars, Eclectus, Caiques, parakeets, Pionus and Poicephalus. Species vary in their temperament, noise level, talking ability, cuddliness with people, and care needs, although how a parrot has been raised usually greatly affects its personality(Dell Vostro A840 battery).

Parrots can make excellent companion animals, and can form close, affectionate bonds with their owners. However they invariably require an enormous amount of attention, care and intellectual stimulation to thrive, akin to that required by a three-year-old child, which many people find themselves unable to provide in the long term. (Dell Vostro A860 battery)Parrots that are bred for pets may be hand fed or otherwise accustomed to interacting with people from a young age to help ensure they will be tame and trusting. However, parrots are not low maintenance pets; they require feeding, grooming, veterinary care, training, environmental enrichment through the provision of toys, exercise, and social interaction (with other parrots or humans) for good health(Dell Inspiron Mini 1012 battery).

Some large parrot species, including large cockatoos, amazons, and macaws, have very long lifespans, with 80 years being reported and record ages of over one hundred.[citation needed] Small parrots, such as lovebirds, hanging parrots, and budgies have shorter life spans of up to 15–20 years. Some parrot species can be quite loud, and many of the larger parrots can be destructive and require a very large cage(SONY PCG-5G2L battery), and a regular supply of new toys, branches, or other items to chew up. The intelligence of parrots means they are quick to learn tricks and other behaviours—both good and bad—that will get them what they want, such as attention or treats.

The popularity, longevity, and intelligence of many of the larger kinds of pet parrot has led to many birds needing to be re-homed during the course of their long lifespans(SONY PCG-5G3L battery). A common problem is that large parrots which are cuddly and gentle as juveniles will mature into intelligent, complex, often demanding adults that can outlive their owners. Due to these problems, and the fact that homeless parrots are not euthanised like dogs and cats, parrot adoption centres and sanctuaries are becoming more common(SONY PCG-F305 battery).

Zoos

Scarlet Macaw riding a tricycle at a show in Spain

Parrot species are found in most zoos, and a few zoos participate in breeding and conservation programs. Some zoos have organized displays of trained parrots and other birds doing tricks.

Trade

Main article: International parrot trade

10,000 Hyacinth Macaws were taken from the wild for the pet trade in the 1980s.[57]

The popularity of parrots as pets has led to a thriving—and often illegal—trade in the birds, and some species are now threatened with extinction(SONY PCG-5J1L battery). A combination of trapping of wild birds and damage to parrot habitats makes survival difficult or even impossible for some species of parrot. Importation of wild caught parrots into the US and Europe is illegal.

The trade continues unabated in some countries. A report published in January 2007 presents a clear picture of the wild-caught parrot trade in Mexico(SONY PCG-5J2L battery), stating: "The majority of parrots captured in Mexico stay in the country for the domestic trade. A small percentage of this capture, 4% to 14%, is smuggled into the USA."[58]

The scale of the problem can be seen in the Tony Silva case of 1996, in which a parrot expert and former director at Tenerife's Loro Parque (Europe's largest parrot park) was jailed in the United States for 82 months and fined $100,000 for smuggling Hyacinth Macaws. (SONY PCG-5K2L battery) (Such birds command a very high price). The case led to calls for greater protection and control over trade in the birds. Different nations have different methods of handling internal and international trade. Australia has banned the export of its native birds since 1960. The United States protects its only native parrot through its Endangered Species Act, and protects other nations' birds through its Wild Bird Conservation Act(SONY PCG-5L1L battery). Following years of campaigning by hundreds of NGOs and outbreaks of avian flu, in July 2007, the European Union halted the importation of all wild birds with a permanent ban on their import. Prior to an earlier temporary ban started in late October 2005, the EU was importing approximately two million live birds a year, about 90% of the international market(SONY PCG-6S2L battery): hundreds of thousands of these were parrots. There are no national laws protecting feral parrot populations in the U.S. Mexico has a licensing system for capturing and selling native birds (though the laws are not well enforced).

Culture

Moche Parrot. 200 A.D. Larco Museum Collection Lima, Peru

Parrots have featured in human writings, story, art, humor, religion and music for thousands of years. From the Roman poet Ovid's "The Dead Parrot"(Latin) (SONY PCG-6S3L battery), (English) to Monty Python's Dead Parrot Sketch millennia later, parrots have existed in the consciousness of many cultures. Recent books about parrots in human culture include Parrot Culture.[60]

In ancient times and current, parrot feathers have been used in ceremonies, and for decoration. The "idea" of the parrot has been used to represent the human condition in medieval literature such as the bestiary. They also have a long history as pets(SONY PCG-6V1L battery).

In Polynesian legend as current in the Marquesas Islands, the hero Laka/Aka is mentioned as having undertaken a long and dangerous voyage to Aotona in what are now the Cook Islands, to obtain the highly prized feathers of a red parrot as gifts for his son and daughter. On the voyage a hundred out of his 140 rowers died of hunger on their way(SONY PCG-6W1L battery), but the survivors reached Aotona and captured enough parrots to fill 140 bags with their feathers.[61] By at least some versions, the feathers were plucked off living parrots without killing them.[62]

Currently parrots feature in many media. There are magazines devoted to parrots as pets, and to the conservation of parrots.[63] Fictional films include Paulie and Rio, and documentaries include The Wild Parrots of Telegraph Hill(SONY PCG-7111L battery).

Parrots have also been considered sacred. The Moche people of ancient Peru worshipped birds and often depicted parrots in their art.[64]

Parrots are used as symbols of nations and nationalism. A parrot is found on the flag of Dominica. The St. Vincent parrot is the national bird of St. Vincent and the Grenadines, a Caribbean nation.

Parrots are popular in Buddhist scripture and there are many writings about them. For example, Amitābha once changed itself into a parrot to aid in converting people(SONY PCG-71511M battery). Another old story tells how after a forest caught fire, the parrot was so concerned it carried water to try and put out the flames. The ruler of heaven was so moved upon seeing the parrot's act, that he sent rain to put out the fire. In Chinese Buddhist iconography, a parrot is sometimes depicted hovering on the upper right side Guan Yin clasping a pearl or prayer beads in its beak(SONY PCG-6W3L battery).

Sayings about parrots colour the modern English language. The verb "parroting" can be found in the dictionary, and means "to repeat by rote." There are also clichés such as the British expression "sick as a parrot"; although this refers to extreme disappointment rather than illness, it may originate from the disease of psittacosis which can be passed to humans. (SONY PCG-7113L battery) The first occurrence of a related expression is in Aphra Behn's 1681 play The False Count.[67]

Feral populations

Main article: Feral parrots

Feral Red-masked Parakeets in San Francisco. The population is the subject of the book and film The Wild Parrots of Telegraph Hill.

Escaped parrots of several species have become established in the wild outside their natural ranges and in some cases outside the natural range of parrots. Among the earliest instances were pet Red Shining-parrots from Fiji which established a population on the islands of southern Tonga(SONY PCG-7133L battery). These introductions were prehistoric and Red-shining Parrots were recorded in Tonga by Captain Cook in the 1770s.[26] Escapees first began breeding in cities in California, Texas and Florida in the 1950s (with unproven earlier claims dating back to the 1920s in Texas and Florida).[30] They have proved surprisingly hardy in adapting to conditions in Europe and North America(SONY PCG-7Z1L battery). They sometimes even multiply to the point of becoming a nuisance or pest, and a threat to local ecosystems, and control measures have been used on some feral populations.[68]

Threats and conservation

A mounted specimen of the Carolina Parakeet, which was hunted to extinction

Community-based conservation has helped arrest the decline of the endangered Ouvea Parakeet

Many parrot species are in decline, and several are extinct. Of the 350 or so living species, 130 are listed as near threatened or worse by the IUCN of which 16 are currently considered Critically Endangered. (SONY PCG-7Z2L battery)  There are several reasons for the decline of so many species, the principal threats being habitat loss and degradation, hunting and, for certain species, the wild-bird trade. Parrots are persecuted because, in some areas, they are (or have been) hunted for food and feathers, and as agricultural pests. For a time, Argentina offered a bounty on Monk Parakeets (an agricultural pest), resulting in hundreds of thousands of birds being killed, though apparently this did not greatly affect the overall population. (SONY PCG-8Y1L battery)

Capture for the pet trade is a threat to many of the rarer or slower to breed parrots. Habitat loss or degradation, most often for agriculture, is a threat to many species. Parrots, being cavity nesters, are vulnerable to the loss of nesting sites and to competition with introduced species for those sites. The loss of old trees is a particular problem in some areas(SONY PCG-8Y2L battery), particularly in Australia where trees suitable for nesting need to be centuries old. Many parrots occur only on islands and are vulnerable to introduced species such as rats and cats, as they lack the appropriate anti-predator behaviours needed to deal with mammalian predators. Controlling such predators can help in maintaining or increasing the numbers of endangered species.[71] Insular species, which have small populations in restricted habitat, are also vulnerable to unpredictable events such as hurricanes and volcanic eruptions(SONY PCG-8Z2L battery).

There are many active conservation groups whose goal is the conservation of wild parrot populations. One of the largest is the World Parrot Trust,[72] an international organisation. The group gives assistance to worthwhile projects as well as producing a magazine[73] and raising funds through donations and memberships, often from pet parrot owners(SONY PCG-8Z1L battery). They state they have helped conservation work in 22 countries. On a smaller scale local parrot clubs will raise money to donate to a conservation cause. Zoo and wildlife centres usually provide public education, to change habits that cause damage to wild populations. Recent conservation measures to conserve the habitats of some of the high-profile charismatic parrot species has also protected many of the less charismatic species living in the ecosystem. (SONY PCG-7112L battery)A popular attraction that many zoos employ is a feeding station for lories and lorikeets, where visitors feed small parrots with cups of liquid food. This is usually done in association with educational signs and lectures.

Several projects aimed specifically at parrot conservation have met with success. Translocation of vulnerable Kakapo, followed by intensive management and supplementary feeding, has increased the population from 50 individuals to 123. (SONY PCG-6W2L battery) In New Caledonia the Ouvea Parakeet was threatened by trapping for the pet trade and loss of habitat. Community based conservation, which eliminated the threat of poaching, has allowed the population to increase from around 600 birds in 1993 to over 2000 birds in 2009.[75]

At present the IUCN recognises 19 species of parrot as extinct since 1600 (the date used to denote modern extinctions). This does not include species like the New Caledonian Lorikeet which has not been officially seen for 100 years yet is still listed as critically endangered(SONY PCG-5K1L battery).

Trade, export and import of all wild-caught parrots is regulated and only permitted under special licensed circumstances in countries party to CITES, the Convention on the International Trade in Endangered Species, that came into force in 1975 to regulate the international trade of all endangered wild caught animal and plant species(SONY VGP-BPS11 battery). In 1975, 24 parrot species were included on Appendix I of CITES, thus prohibiting commercial international trade in these birds. Since that initial listing, continuing threats from international trade led CITES to add an additional 32 parrot varieties to Appendix I.[77] All the other parrot species are protected on Appendix II of CITES. In addition, individual countries may have laws to regulate trade in certain species(SONY VGP-BPL11 battery).

Whale (origin Old English hwæl) is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti (toothed whales). This suborder also includes the sperm whale, killer whale, pilot whale, and beluga whaleSONY PCG-8113M battery. The other Cetacean suborder Mysticeti (baleen whales) are filter feeders that eat small organisms caught by straining seawater through a comblike structure found in the mouth called baleen. This suborder includes the blue whale, the humpback whale, the bowhead whale and the minke whale. All Cetacea have forelimbs modified as fins, a tail with horizontal flukes, and nasal openings (blowholes) on top of the headSONY PCG-8112M battery .

Whales range in size from the blue whale, the largest animal known ever to have existed[3] at 30 m (98 ft) and 180 tonnes (180 long tons; 200 short tons), to various pygmy species, such as the pygmy sperm whale at 3.5 m (11 ft).

Whales collectively inhabit all the world's oceans and number in the millions, with annual population growth rate estimates for various species ranging from 3% to 13%.[4] For centuries, whales have been hunted for meat and as a source of raw materialsSONY PCG-7134M battery. By the middle of the 20th century, however, industrial whaling had left many species seriously endangered, leading to the end of whaling in all but a few countries.

Taxonomy

See also: List of whale species

Cetaceans are divided into two suborders:

The largest suborder, Mysticeti (baleen whales) are characterized by baleen, a sieve-like structure in the upper jaw made of keratin, which it uses to filter plankton from the water.

Odontoceti (toothed whales) bear sharp teeth for hunting. Odontoceti also include dolphins and porpoisesSONY PCG-7131M battery .

Both cetaceans and artiodactyl are now classified under the super-order Cetartiodactyla which includes both whales and hippopotamuses. Whales are the hippopotamus's closest living relatives.[5]

Evolution

Ambulocetus natans – a primitive cetacean

See also: Evolution of cetaceans

All cetaceans, including whales, dolphins and porpoises, are descendants of land-living mammals of the Artiodactyl order (even-toed ungulates). Both are related to the Indohyus (an extinct semi-aquatic deer-like ungulate) from which they split around 54 million years ago. SONY PCG-7122M battery  These primitive cetaceans probably first took to the sea about 50 million years ago and became fully aquatic about 5–10 million years later.[8]

Anatomy

Like all mammals, whales breathe air, are warm-blooded, nurse their young with milk from mammary glands, and have body hair.[9] Beneath the skin lies a layer of fat called blubber, which stores energy and insulates the body. Whales have a spinal column, a vestigial pelvic bone, and a four-chambered heartSONY PCG-7121M battery. The neck vertebrae are typically fused, trading flexibility for stability during swimming.

Blowhole(s)

Features of a blue whale

Whales breathe via blowholes; baleen whales have two and toothed whales have one. These are located on the top of the head, allowing the animal to remain mostly submerged whilst breathing. Breathing involves expelling excess water from the blowhole, forming an upward spout, followed by inhaling air into the lungs. Spout shapes differ among species and can help with identificationSONY PCG-7113M battery .

Appendages

The body shape is fusiform and the modified forelimbs, or fins, are paddle-shaped. The end of the tail is composed of two flukes, which propel the animal by vertical movement, as opposed to the horizontal movement of a fish tail. Although whales do not possess fully developed hind limbs, some (such as sperm whales and baleen whales) possess discrete rudimentary appendagesSONY PCG-7112M battery , which may even have feet and digits. Most species have a dorsal fin.

Dentition

Toothed whales, such as the sperm whale, possess teeth with cementum cells overlying dentine cells. Unlike human teeth, which are composed mostly of enamel on the portion of the tooth outside of the gum, whale teeth have cementum outside the gum. Only in larger whales, where the cementum has been worn away on the tip of the tooth, does enamel show. SONY PCG-8Z3M battery

Instead of teeth, Baleen whales have a row of plates on the upper side of their jaws that resemble the "teeth" of a comb.

Ears

The whale ear has specific adaptations to the marine environment. In humans, the middle ear works as an impedance matcher between the outside air’s low impedance and the cochlear fluid’s high impedance. In aquatic mammals such as whales, however, there is no great difference between the outer and inner environmentsSONY PCG-8Z2M battery. Instead of sound passing through the outer ear to the middle ear, whales receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear.[11] The whale ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater. SONY PCG-8Z1M battery

Life history and behavior

Reproduction

Males are called 'bulls', females, 'cows' and newborns, 'calves'. Most species do not maintain fixed partnerships and females have several mates each season.

The female delivers usually a single calf tail-first to minimize the risk of drowning. Whale cows nurse by actively squirting milk, so fatty that it has the consistency of toothpaste, into the mouths of their young.[13] Nursing continues for more than a year in many speciesSONY PCG-8Y3M battery, and is associated with a strong bond between mother and calf. Reproductive maturity occurs typically at seven to ten years. This mode of reproduction produces few offspring, but increases survival probability.

Socialization

Whales are known to teach, learn, cooperate, scheme, and even grieve.[15] The neocortex of many species of whale is home to elongated spindle neurons thatSONY PCG-8Y2M battery, prior to 2007, were known only in hominids. In humans these cells are involved in social conduct, emotions, judgment, and theory of mind. Whale spindle neurons are found in areas of the brain homologous to where they are found in humans, suggesting that they perform a similar function. SONY PCG-7Z1M battery

Sleep

A humpback whale breaching.

Unlike most animals, whales are conscious breathers. All mammals sleep, but whales cannot afford to become unconscious for long because they may drown. It is thought that only one hemisphere of the whale's brain sleeps at a time, so they rest but are never completely asleep. SONY PCG-6W2M battery

Surfacing behavior

Main article: Whale surfacing behaviour

Many whales exhibit behaviors such as breaching and tail slapping that expose large parts of their bodies to the air.

Lifespan

Whale lifespans vary among species and are not well characterized. Whaling left few older individuals to observe directly. R.M. Nowak of Johns Hopkins University estimated that humpback whales may live as long as 77 years.SONY PCG-5J5M battery  In 2007, a 19th century lance fragment was found in a bowhead whale off Alaska, suggesting the individual could be between 115 and 130 years old.[21] Aspartic acid racemization in the whale eye, combined with a harpoon fragment, indicated an age of 211 years for another male, which, if true would make bowheads the longest-lived extant mammal speciesSONY PCG-5K2M battery . The accuracy of this technique has been questioned because racemization did not correlate well with other dating methods.[24]

Vocalization

Humpback Whale "Song"

Recording of Humpback Whales singing and Clicking.

Problems listening to this file? See media help.

Some species, such as the humpback whale, communicate using melodic sounds, known as whale song. These sounds can be extremely loud, depending on the species. Sperm whales have only been heard making clicks, while toothed whales (Odontoceti) SONY PCG-5K1M battery use echolocation that can generate about 20,000 watts of sound (+73 dBm or +43 dBw[25]) and be heard for many miles. Whale vocalization is likely to serve many purposes, including echolocation, mating, and identification.[citation needed]

Ecology

Whales are generally classed as predators, but their food ranges from microscopic plankton to very large animalsSONY PCG-5J4M battery.

Toothed whales eat fish and squid which they hunt by use of echolocation. Killer whales sometimes eat other marine mammals, including whales.

Baleen whales such as humpbacks and blues, when feeding in higher latitudes (such as the Southern Ocean), eat mostly krill. They imbibe enormous amounts of seawater which they expel through their baleen platesSONY PCG-5J1M battery . The water is then expelled and the krill is retained on the plates and then swallowed.[13] Whales do not drink seawater but indirectly extract water from their food by metabolizing fat.

Whale pump

A study in 2010 has attributed to whales a positive influence on the productivity of ocean fisheries, in what has been termed a "whale pump." Whales carry nutrients such as nitrogen from the depths back to the surfaceSONY PCG-5G2M battery. This functions as an upward biological pump, reversing the assumption of some scientists that whales accelerate the loss of nutrients to the bottom. They note that this nitrogen input in the Gulf of Maine is "more than the input of all rivers combined," some 23,000 metric tons each year."

Relation to humans

Whaling

Main article: Whaling

Dutch whalers near Spitsbergen. Abraham Storck, 1690

World map of International Whaling Commission (IWC) members/non-members(member countries in blue) Sony VAIO PCG-8131M battery

World population graph of Blue Whales (Balaenoptera musculus)

Some species of large whales are listed as endangered by multinational organizations such as CITES along with governments and advocacy groups primarily due to whaling's impacts. They have been hunted commercially for whale oil, meat, baleen and ambergris (a perfume ingredient from the intestine of sperm whales) since the 17th century. Sony VAIO PCG-8152M battery At its peak in 1846, the American whaling industry employed more than 70,000 people and 736 vessels.[29] More than 2 million were taken in the 20th century,[30] and by the middle of the century, many populations were severely depleted.

The International Whaling Commission banned commercial whaling in 1986.[31] The ban is not absolute, however, and some whaling continues under the auspices of scientific researchSony VAIO PCG-31311M battery (sometimes not proved[32]) or aboriginal rights; current whaling nations are Norway, Iceland and Japan and the aboriginal communities of Siberia, Alaska and northern Canada.

Bycatch

Several species of small whales are caught as bycatch in fisheries for other species. In the Eastern Tropical Pacific tuna fishery, thousands of dolphins drowned in purse-seine nets, until preventive measures were introduced. Gear and deployment modifications, and eco-labelling (dolphin-safe or dolphin-friendly brands of tuna), have contributed to a reduction in dolphin mortality by tuna vesselsSony VAIO PCG-31111M battery.

Naval sonar

See also: Marine Mammals and Sonar

Environmentalists speculate that advanced naval sonar endangers some cetaceans, including whales. In 2003 British and Spanish scientists suggested in Nature that the effects of sonar trigger whale beachings and to signs that such whales have experienced decompression sickness.[33] Responses in Nature the following year discounted the explanation. Sony VAIO PCG-8112M battery

Mass beachings occur in many species, mostly beaked whales that use echolocation for deep diving. The frequency and size of beachings around the world, recorded over the last 1,000 years in religious tracts and more recently in scientific surveys, have been used to estimate the population of various whale species by assuming that the proportion of the total whale population beaching in any one year is constantSony VAIO PCG-7186M battery. Beached whales can give other clues about population conditions, especially health problems. For example, bleeding around ears, internal lesions, and nitrogen bubbles in organ tissue suggest decompression sickness.[15]

Following public concern, the U.S. Defense department was ordered by the 9th Circuit Court to strictly limit use of its Low Frequency Active Sonar during peacetimeSony VAIO PCG-7171M battery. Attempts by the UK-based Whale and Dolphin Conservation Society to obtain a public inquiry into the possible dangers of the Royal Navy's equivalent (the "2087" sonar launched in December 2004) failed as of 2008. The European Parliament has requested that EU members refrain from using the powerful sonar system until an environmental impact study has been carried outSony VAIO PCG-9Z1M battery.

Other environmental disturbances

See also: Cetacean bycatch

Other human activities have been suggested by marine biologists to adversely impact whale populations, such as collisions with ships and propellers, poisoning by waste contaminants and the unregulated use of fishing gear that catches anything that swims into it.[citation needed]

In mythology

Whale weather-vane atop the Nantucket Historical Association Whaling Museum displaying a Sperm WhaleSony VAIO PCG-5S1M battery.

Whales were little understood for most of human history as they spend up to 90% of their lives underwater, only surfacing briefly to breathe.[35] They also include the largest animals on the planet. Many cultures, even those that have hunted them, hold them in awe and feature them in their mythologiesSony VAIO PCG-5P1M battery.

In China, Yu-kiang, a whale with the hands and feet of a man was said to rule the ocean.[36]

In the Tyrol region of Austria it was said that if a sunbeam were to fall on a maiden entering womanhood, she would be carried away in the belly of a whale.[36]

Paikea, the youngest and favourite son of the chief Uenuku from the island of Mangaia in the present day Cook Islands in New Zealand was said by the Kati Kuri people of Kaikoura to have come from the Pacific Islands on the back of a whale many centuries before. Sony VAIO PCG-5N2M battery The novel and movie Whale Rider follow the trials of a girl named Paikia, who lives in such a culture.

The whale features in Inuit creation myths. When ‘Big Raven', a deity in human form, found a stranded whale, he was told by the Great Spirit where to find special mushrooms that would give him the strength to drag the whale back to the sea and thus return order to the world.[38]

The Tlingit people of northern Canada said that the Orcas were created when the hunter Natsihlane carved eight fish from yellow cedar, Sony VAIO PCG-3C2M battery sang his most powerful spirit song and commanded the fish to leap into the water.[38]

In Icelandic legend a man threw a stone at a fin whale and hit the blowhole, causing the whale to burst. The man was told not to go to sea for twenty years but in the nineteenth year he went fishing and a whale came and killed him. Sony VAIO PCG-8161M battery

In East African legend King Sulemani asked God that He might permit him to feed all the beings on earth. A whale came and ate until there was no corn left and then told Sulemani that he was still hungry and that there were 70,000 more in his tribe. Sulemani then prayed to God for forgiveness and thanked the creature for teaching him a lesson in humility.Sony VAIO PCG-8141M battery

Some cultures associate divinity with whales, such as among Ghanaians and Vietnamese, who occasionally hold funerals for beached whales, a throwback to Vietnam's ancient sea-based Austro-asiatic culture. The whale is a revered creature to Vietnamese fishermen. They are respectfully addressed as "Lord". If one finds a stranded whale corpse, one is in charge of holding the funeral for the "Lord" as if it was one's own parentSony VAIO PCG-3J1M battery.

The story of Jonah being swallowed by a whale also is told in the Qur'an.[43]

Whales in the Bible

The Bible, 1611 Authorized Version, expressly mentions whales four times:

Genesis 1:21 And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. Sony VAIO PCG-3H1M battery

Job 7:12 Am I a sea, or a whale, that thou settest a watch over me?

Ezekiel 32:2 Son of man, take up a lamentation for Pharaoh king of Egypt, and say unto him, Thou art like a young lion of the nations, and thou art as a whale in the seas: and thou camest forth with thy rivers, and troubledst the waters with thy feet, and fouledst their rivers.

Matthew 12:40 For as Jonas was three days and three nights in the whale’s belly; so shall the Son of man be three days and three nights in the heart of the earthSony VAIO PCG-3F1M battery.

The translators in that latter verse above thereby identified the "great fish" of the book of Jonah as a whale. It is apparent that Jeremiah recognized that some great fish are mammals. The English word "monster", (used in the ordinary sense of a "huge animal",) is used in the Bible in Jeremiah's Lamentations to refer to whales
Sony VAIO PCG-3C1M battery:

Lamentations 4:3 Even the sea monsters draw out the breast, they give suck to their young ones: the daughter of my people is become cruel, like the ostriches in the wilderness.

Dolphins are marine mammals closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's dolphin), up to 9.5 m (30 ft) and 10 tonnesSony VAIO PCG-9Z2L battery (9.8 long tons; 11 short tons) (the orca or killer whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, eating mostly fish and squid. The family Delphinidae is the largest in the Cetacean order, and evolved relatively recently, about ten million years ago, during the Miocene. Dolphins are among the most intelligent animals, and their often friendly appearance and seemingly playful attitude have made them very popular in human cultureSony VAIO PCG-9Z1L battery.

Etymology

The name is originally from Greek δελφίς (delphís), "dolphin",[1] which was related to the Greek δελφύς (delphus), "womb".[2] The animal's name can therefore be interpreted as meaning "a 'fish' with a womb".[3] The name was transmitted via the Latin delphinus[4] (the romanization of the later Greek δελφῖνος – delphinos[5]), which in Medieval Latin became dolfinus and in Old French daulphinSony VAIO PCG-9131L battery, which reintroduced the ph into the word. The term mereswine (that is, "sea pig") has also historically been used.[6]

The word is used in a few different ways. It can mean:

any member of the family Delphinidae (oceanic dolphins),

any member of the family Delphinidae or the superfamily Platanistoidea (oceanic and river dolphins),

any member of the suborder Odontoceti (toothed whales; these include the above families and some others) Sony VAIO PCG-8161L battery,

and is used casually as a synonym for bottlenose dolphin, the most common and familiar species of dolphin.

This article uses the second definition and does not describe porpoises (suborder Odontoceti, family Phocoenidae). Orcas and some closely related species belong to the Delphinidae family and therefore qualify as dolphins, even though they are called whales in common languageSony VAIO PCG-8152L battery.

A group of dolphins is called a "school" or a "pod". Male dolphins are called "bulls", females "cows" and young dolphins are called "calves".[7]

Hybridization

In 1933, three strange dolphins beached off the Irish coast; they appeared to be hybrids between Risso's and bottlenose dolphins.[9] This mating was later repeated in captivity, producing a hybrid calf. In captivity, a bottlenose and a rough-toothed dolphin produced hybrid offspring.[10] A common-bottlenose hybrid lives at SeaWorld California. Sony VAIO PCG-8141L battery Other dolphin hybrids live in captivity around the world or have been reported in the wild, such as a bottlenose-Atlantic spotted hybrid.[12] The best known hybrid is the wolphin, a false killer whale-bottlenose dolphin hybrid. The wolphin is a fertile hybrid. Two wolphins currently live at the Sea Life Park in Hawaii; the first was born in 1985 from a male false killer whale and a female bottlenose. Wolphins have also been observed in the wild.Sony VAIO PCG-8131L battery

Evolution and anatomy

The anatomy of a dolphin, showing its skeleton, major organs, tail, and body shape

Pacific white-sided dolphin skeleton (missing pelvic bones), on exhibit at The Museum of Osteology, Oklahoma City, Oklahoma

Evolution

See also: Evolution of cetaceans

Dolphins, along with whales and porpoises, are descendants of terrestrial mammals, most likely of the Artiodactyl order. The ancestors of the modern-day dolphins entered the water roughly 50 million years ago, in the Eocene epochSony VAIO PCG-81312L battery.

Hind limb buds are apparent on an embryo of a spotted dolphin in the fifth week of development as small bumps (hind limb buds) near the base of the tail. The pin is approximately 2.5 cm (1.0 in) long.

Modern dolphin skeletons have two small, rod-shaped pelvic bones thought to be vestigial hind limbs. In October 2006, an unusual bottlenose dolphin was captured in Japan; it had small fins on each side of its genital slitSony VAIO PCG-81214L battery, which scientists believe to be a more pronounced development of these vestigial hind limbs.[14]

Anatomy

Dolphins have a streamlined fusiform body, adapted for fast swimming. The tail fin, called the fluke, is used for propulsion, while the pectoral fins together with the entire tail section provide directional control. The dorsal fin, in those species that have one, provides stability while swimming. Though it varies by speciesSony VAIO PCG-81115L battery, basic coloration patterns are shades of grey, usually with a lighter underside, often with lines and patches of different hue and contrast.

The head contains the melon, a round organ used for echolocation. In many species, elongated jaws form a distinct beak; species such as the bottlenose have a curved mouth which looks like a fixed smile. Some species have up to 250 teeth. Dolphins breathe through a blowhole on top of their head. The trachea is anterior to the brainSony VAIO PCG-81114L battery. The dolphin brain is large and highly complex, and is different in structure from that of most land mammals.

Unlike most mammals, dolphins do not have hair, except for a few hairs around the tip of their rostrum which they lose shortly before or after birth.[15] The only exception to this is the Boto river dolphin, which has persistent small hairs on the rostrum. Sony VAIO PCG-81113L battery

Dolphins' reproductive organs are located on the underside of the body. Males have two slits, one concealing the penis and one further behind for the anus. The female has one genital slit, housing the vagina and the anus. Two mammary slits are positioned on either side of the female's genital slitSony VAIO PCG-7142L battery.

Though the exact methods used to achieve this are not known, dolphins can tolerate and recover from extreme injuries, such as shark bites. The healing process is rapid and even very deep wounds do not cause dolphins to hemorrhage to death. Furthermore, even gaping wounds restore in such a way that the animal's body shape is restored, and infection of such large wounds seems rare. Sony VAIO PCG-7141L battery

A study at the U.S. National Marine Mammal Foundation revealed that dolphins, like humans, develop a natural form of type 2 diabetes, which may lead to a better understanding of the disease and new treatments for both humans and dolphins.[18]

Senses

Most dolphins have acute eyesight, both in and out of the water, and they can hear frequencies ten times or more above the upper limit of adult human hearingSony VAIO PCG-71111L battery.[19] Though they have a small ear opening on each side of their head, it is believed hearing underwater is also, if not exclusively, done with the lower jaw, which conducts sound to the middle ear via a fat-filled cavity in the lower jaw bone. Hearing is also used for echolocation, which all dolphins have. Dolphin teeth are believed to function as antennae to receive incoming sound and to pinpoint the exact location of an object. Sony VAIO PCG-61411L batteryBeyond locating an object, echolocation also provides the animal with an idea on the object's shape and size, though how exactly this works is not yet understood.[21] The Indus Dolphin is effectively blind. This may be because not much light penetrates the waters of the Indus river (due to suspended sediments), making eyes futile. Sony VAIO PCG-61112L battery

The dolphin's sense of touch is also well-developed, with free nerve endings densely packed in the skin, especially around the snout, pectoral fins and genital area. However, dolphins lack an olfactory nerve and lobes, and thus are believed to have no sense of smell.[23] They do have a sense of taste and show preferences for certain kinds of fishSony VAIO PCG-61111L battery. Since dolphins spend most of their time below the surface, tasting the water could function like smelling, in that substances in the water can signal the presence of objects that are not in the dolphin’s mouth.

Though most dolphins do not have hair, they do have hair follicles that may perform some sensory function.[24] The small hairs on the rostrum of the Boto river dolphin are believed to function as a tactile sense possibly to compensate for the Boto's poor eyesight. Sony VAIO PCG-5T4L battery

Behavior

A pod of Indo-Pacific bottlenose dolphins in the Red Sea.

See also: Whale surfacing behaviour

Dolphins are often regarded as one of Earth's most intelligent animals, though it is hard to say just how intelligent. Comparing species' relative intelligence is complicated by differences in sensory apparatus, response modes, and nature of cognition. Furthermore, the difficulty and expense of experimental work with large aquatic animals has so far prevented some tests and limited sample size and rigor in othersSony VAIO PCG-5T3L battery. Compared to many other species, however, dolphin behavior has been studied extensively, both in captivity and in the wild. See cetacean intelligence for more details.

Social behavior

Dolphins surfing at Snapper Rocks, Queensland, Australia

Dolphins are social, living in pods of up to a dozen individuals. In places with a high abundance of food, pods can merge temporarily, forming a superpod; such groupings may exceed 1,000 dolphins. Individuals communicate using a variety of clicks, whistles-like sounds and other vocalizationsSony VAIO PCG-5T2L battery. Membership in pods is not rigid; interchange is common. However, dolphins can establish strong social bonds; they will stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if needed.[26] This altruism does not appear to be limited to their own species however. The dolphin Moko in New Zealand has been observed guiding a female Pygmy Sperm Whale together with her calf out of shallow water where they had stranded several timesSony VAIO PCG-5S3L battery.[27] They have also been seen protecting swimmers from sharks by swimming circles around the swimmers[28][29] or charging the sharks to make them go away.[30]

Dolphins also display culture, something long believed to be unique to humans (and possibly other primate species). In May 2005, a discovery in Australia found Indo-Pacific bottlenose dolphins (Tursiops aduncus) teaching their young to use tools. They cover their snouts with sponges to protect them while foragingSony VAIO PCG-5S2L battery. This knowledge is mostly transferred by mothers to daughters, unlike simian primates, where knowledge is generally passed on to both sexes. Using sponges as mouth protection is a learned behavior.[31] Another learned behavior was discovered among river dolphins in Brazil, where some male dolphins use weeds and sticks as part of a sexual display.Sony VAIO PCG-5S1L battery

Dolphins engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. Male dolphins engage in such acts of aggression apparently for the same reasons as humans: disputes between companions and competition for females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile as a result of losing a fightSony VAIO PCG-5R2L battery.

Male bottlenose dolphins have been known to engage in infanticide. Dolphins have also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same diet as dolphins, and are therefore not competitors for food supplies. Sony VAIO PCG-5R1L battery

Reproduction and sexuality

See also: Bottlenose dolphin#Reproduction

Dolphin copulation happens belly to belly; though many species engage in lengthy foreplay, the actual act is usually brief, but may be repeated several times within a short timespan. The gestation period varies with species; for the small Tucuxi dolphin, this period is around 11 to 12 months, while for the orca, the gestation period is around 17 monthsSony VAIO PCG-5P4L battery. Typically dolphins give birth to a single calf, which is, unlike most other mammals, born tail first in most cases.[34] They usually become sexually active at a young age, even before reaching sexual maturity. The age of sexual maturity varies by species and gender.

Dolphins are known to have sex for reasons other than reproduction[citation needed], sometimes also engaging in homosexual behaviorSony VAIO PCG-5P2L battery. Various species sometimes engage in sexual behavior including copulation with other dolphin species. Sexual encounters may be violent, with male dolphins sometimes showing aggressive behavior towards both females and other males.[35] Occasionally, dolphins behave sexually towards other animals, including humans. Sony VAIO PCG-5N4L battery

Feeding

Various methods of feeding exist among and within species, some apparently exclusive to a single population. Fish and squid are the main food, but the false killer whale and the orca also feed on other marine mammals.

One common feeding method is herding, where a pod squeezes a school of fish into a small volume, known as a bait ballSony VAIO PCG-5N2L battery. Individual members then take turns plowing through the ball, feeding on the stunned fish. Coralling is a method where dolphins chase fish into shallow water to catch them more easily. In South Carolina, the Atlantic bottlenose dolphin takes this further with "strand feeding", driving prey onto mud banks for easy access.[37] In some places, orcas come to the beach to capture sea lionsSony VAIO PCG-51513L battery. Some species also whack fish with their flukes, stunning them and sometimes knocking them out of the water.

Reports of cooperative human-dolphin fishing date back to the ancient Roman author and natural philosopher Pliny the Elder.[38] A modern human-dolphin partnership currently operates in Laguna, Santa Catarina, BrazilSony VAIO PCG-51511L battery. Here, dolphins drive fish towards fishermen waiting along the shore and signal the men to cast their nets. The dolphins’ reward is the fish that escape the nets.

Vocalizations

Spectrogram of dolphin vocalizations. Whistles, whines, and clicks are visible as upside down V's, horizontal striations, and vertical lines, respectively.

Dolphins are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: frequency modulated whistles, burst-pulsed sounds and clicksSony VAIO PCG-51412L battery. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to the way human vocal cords function,[41] and through burst-pulsed sounds, though the nature and extent of that ability is not known. The clicks are directional and are for echolocation, often occurring in a short series called a click train. The click rate increases when approaching an object of interestSony VAIO PCG-51411L battery. Dolphin echolocation clicks are amongst the loudest sounds made by marine animals.[42]

In 2011 researchers in the United States and Great Britain, using a CymaScope — an instrument which produces visible patterns from sound — have found that part of dolphin communication consists of receiving and transmitting sound pictures. It is almost certain that to some extent this ability is shared by the entire dolphin familySony VAIO PCG-51312L battery.

Jumping and playing

Pacific white-sided dolphins porpoising

Dolphins occasionally leap above the water surface, and sometimes perform acrobatic figures (for example, the spinner dolphin). Scientists are not certain about the purpose(s) of the acrobatics. Possibilities include locating schools of fish by looking at above-water signs like feeding birds, communicating with other dolphins, dislodging parasites or simple amusementSony VAIO PCG-51311L battery.

Play is an important part of dolphin culture. Dolphins play with seaweed and play-fight with other dolphins. At times they harass other local creatures, like seabirds and turtles. Dolphins enjoy riding waves and frequently surf coastal swells and the bow waves of boats, at times “leaping” between the dual bow waves of a moving catamaranSony VAIO PCG-51211L battery. Occasionally, they playfully interact with swimmers. Captive dolphins have been observed in aquariums engaging in complex play behavior which involves the creation and manipulation of bubble rings.

Sleeping

Further information: Sleep (non-human)

Sleeping dolphin in captivity: a tail kick reflex keeps the dolphin's blowhole above the water

GenerallySony VAIO PCG-41112L battery, dolphins sleep with only one brain hemisphere in slow-wave sleep at a time, thus maintaining enough consciousness to breathe and to watch for possible predators and other threats. Earlier sleep stages can occur simultaneously in both hemispheres. In captivity, dolphins seemingly enter a fully asleep state where both eyes are closed and there is no response to mild external stimuliSony VAIO PCG-3A4L battery. In this case, respiration is automatic; a tail kick reflex keeps the blowhole above the water if necessary. Anesthetized dolphins initially show a tail kick reflex.[51] Though a similar state has been observed with wild sperm whales, it is not known if dolphins in the wild reach this state.[52] The Indus river dolphin has a sleep method that is different from that of other dolphin speciesSony VAIO PCG-3A3L battery. Living in water with strong currents and potentially dangerous floating debris, it must swim continuously to avoid injury. As a result, this species sleeps in very short bursts which last between 4 and 60 seconds.[53]

Threats

Natural threats

Except for humans (discussed below), dolphins have few natural enemies. Some species or specific populations have none, making them apex predators. For most of the smaller species of dolphins, only a few of the larger sharks, such as the bull sharkSony VAIO PCG-3A2L battery, dusky shark, tiger shark and great white shark, are a potential risk, especially for calves. Some of the larger dolphinic species, especially orcas (killer whales), may also prey on smaller dolphins, but this seems rare. Dolphins also suffer from a wide variety of diseases and parasites.

Human threats

See also: Dolphin drive hunting and Cetacean bycatch

Dead Atlantic white-sided dolphins in Hvalba on the Faroe Islands, killed in a drive huntSony VAIO PCG-3A1L battery

Some dolphin species face an uncertain future, especially some river dolphin species such as the Amazon river dolphin, and the Ganges and Yangtze river dolphin, which are critically or seriously endangered. A 2006 survey found no individuals of the Yangtze river dolphin, which now appears to be functionally extinct. Sony VAIO PCG-394L battery

Pesticides, heavy metals, plastics, and other industrial and agricultural pollutants that do not disintegrate rapidly in the environment concentrate in predators such as dolphins.[55] Injuries or deaths due to collisions with boats, especially their propellers, are also common.

Various fishing methods, most notably purse seine fishing for tuna and the use of drift and gill nets, unintentionally kill many dolphinsSony VAIO PCG-393L battery. Accidental by-catch in gill nets and incidental captures in antipredator nets that protect marine fish farms are common and pose a risk for mainly local dolphin populations. In some parts of the world, such as Taiji in Japan and the Faroe Islands, dolphins are traditionally considered as food, and are killed in harpoon or drive hunts.[59] Dolphin meat is high in mercury, and may thus pose a health danger to humans when consumedSony VAIO PCG-391L battery.

Dolphin safe labels attempt to reassure consumers fish and other marine products have been caught in a dolphin-friendly way. The original deal with "Dolphin safe" labels was brokered in the 1980s between marine activists and the major tuna companies, and involved decreasing incidental dolphin kills by up to 50% by changing the type of nets being used to catch the tunaSony VAIO PCG-384L battery. It should be noted that the dolphins are netted only while fishermen are in pursuit of smaller tuna. Albacore are not netted this way, making albacore the only truly dolphin-safe tuna.

Loud underwater noises, such as those resulting from naval sonar use, live firing exercises, or certain offshore construction projects, such as wind farms, may be harmful to dolphins, increasing stress, damaging hearing, and causing decompression sickness by forcing them to surface too quickly to escape the noiseSony VAIO PCG-382L battery.

Relationships with humans

Mythology

Fresco of Dolphins, ca. 1600 BC, from Knossos, Crete.

See also: Dolphins in mythology

Dolphins have long played a role in human culture. Dolphins are common in Greek mythology and there are many coins from ancient Greece which feature a man or boy or deity riding on the back of a dolphin. The Ancient Greeks welcomed dolphins; spotting dolphins riding in a ship’s wake was considered a good omen.[64] In Hindu mythology, the Ganges River Dolphin is associated with Ganga, the deity of the Ganges riverSony VAIO PCG-381L battery.

Popular culture

Luke Halpin with one of the dolphin performers in the 1963 film, Flipper.

In more recent times, the 1963 film Flipper and the subsequent 1964 television series popularized dolphins in Western society. The series, created by Ivan Tors, portrayed a dolphin as a kind of seagoing version of Lassie, the collie made popular in the 1950s TV series. Flipper was a Bottlenose Dolphin who understood commands and always behaved heroicallySony VAIO PCG-7185L battery. Flipper was remade as a film in 1996.

The 1973 movie The Day of the Dolphin portrays kidnapped dolphins performing a naval military assassination using explosives. This was also explored in the similarly named The Simpsons Treehouse of Horror episode, "Night of the Dolphin", where Lisa frees a dolphin at an aquarium exhibit and unwittingly initiates their plan to overthrow the land-dwellers and live in their placeSony VAIO PCG-7184L battery. The 1990s science fiction television series seaQuest DSV featured a bottle-nose named Darwin who could communicate using a vocoder, a fictional invention which translated clicks and whistles to English and back.

The 1995 movie Johnny Mnemonic portrays an ex-military dolphin named Jones who tries to find a password for Johnny by decrypting data in the latter's headSony VAIO PCG-7183L battery.

Killer whales have also been portrayed in film, though to a lesser extent than bottlenosed dolphins. The 1977 horror movie Orca portrayed killer whales as intelligent and capable of pair-bonding and aggressive behavior. In the movie, a male killer whale takes revenge on fishermen after they kill his mate. The 1993 movie Free Willy made a star of the Orca playing Willy, KeikoSony VAIO PCG-7182L battery.

Dolphinaria

See also: Dolphinarium

The renewed popularity of dolphins in the 1960s resulted in the appearance of many dolphinaria around the world, making dolphins accessible to the public. Criticism and animal welfare laws forced many to close, although hundreds still exist around the world. In the United States, the best known are the SeaWorld marine mammal parksSony VAIO PCG-7181L battery.

Welfare

Organizations such as the Mote Marine Laboratory rescue and rehabilitate sick, wounded, stranded or orphaned dolphins, while others, such as the Whale and Dolphin Conservation Society and Hong Kong Dolphin Conservation Society, work on dolphin conservation and welfare. India has declared the Dolphin as its national aquatic animal in an attempt to protect the endangered Ganges River DolphinSony VAIO PCG-7174L battery. The Vikramshila Gangetic Dolphin Sanctuary has been created in the Ganges river for the protection of the animals.

Various scientists who have researched Dolphin behaviour have proposed that their unusually high intelligence compared to other animals means that dolphins should be seen as non-human persons that should have their own specific rights, and that it is morally unacceptable to keep them captive for entertainment purposesSony VAIO PCG-7173L battery, or to kill them; either intentionally for consumption or as by-catch.

Attack on humans

Tilikum at SeaWorld. In 2010 he attacked and killed his trainer Dawn Brancheau, in his third fatal incident.

Although dolphins generally interact well with humans, some attacks have occurred, most of them resulting in small injuries.[67] The attacks can occur both in the wild and captivity.

Orcas, the largest species of dolphin, have been involved in fatal attacks on humans in captivitySony VAIO PCG-7172L battery. The record-holder of documented orca fatal attacks is a male named Tilikum, that belongs to SeaWorld and has played a role in the death of three people in three different incidents (1991, 1999 and 2010).[68] There are documented incidents in the wild too, but none of them fatal.

Fatal attacks from other species are less common, but there is a registered occurrence in the coast of Brazil in 1994, when a man died after being attacked by a bottlenose dolphin named TiãoSony VAIO PCG-7171L battery. It should be noted that Tião had suffered harassment by human visitors, including attempts to stick ice cream sticks down his blowhole.[72] Non-fatal incidents occur more frequently, both in wild and captivity.

While dolphin attacks occur far less frequently than attacks by other sea animals, such as sharks, some scientists are worried about the careless programs of human-dolphin interaction. Dr. Andrew J. Read, a biologist at the Duke University Marine Laboratory who studies dolphin attacksSony VAIO PCG-7162L battery, points out that dolphins are large and wild predators, so people should be more careful when they interact with them.[67]

Therapy

Dolphins are an increasingly popular choice of animal-assisted therapy for psychological problems and developmental disabilities. For example, a 2005 study found dolphins an effective treatment for mild to moderate depression. Sony VAIO PCG-7161L battery However, this study was criticized on several grounds. For example, it is not known whether dolphins are more effective than common pets.[74] Reviews of this and other published dolphin-assisted therapy (DAT) studies have found important methodological flaws and have concluded that there is no compelling scientific evidence that DAT is a legitimate therapy or that it affords more than fleeting mood improvement. Sony VAIO PCG-7154L battery

Military

A military dolphin

See also: Military dolphin

A number of militaries have employed dolphins for various purposes from finding mines to rescuing lost or trapped humans. The military use of dolphins, however, drew scrutiny during the Vietnam War when rumors circulated that the United States Navy was training dolphins to kill Vietnamese divers. Sony VAIO PCG-7153L battery The United States Navy denies that at any point dolphins were trained for combat. Dolphins are still being trained by the United States Navy on other tasks as part of the U.S. Navy Marine Mammal Program. The Russian military is believed to have closed its marine mammal program in the early 1990s. In 2000 the press reported that dolphins trained to kill by the Soviet Navy had been sold to Iran. Sony VAIO PCG-7152L battery

Literature

Dolphins are also common in contemporary literature, especially science fiction novels. Dolphins play a military role in William Gibson's short story Johnny Mnemonic, in which cyborg dolphins find submarines and decode encrypted information. Dolphins play a role as sentient patrollers of the sea enhanced with a deeper empathy toward humans in Anne McCaffrey's The Dragonriders of Pern seriesSony VAIO PCG-7151L battery. In the Known Space universe of author Larry Niven, dolphins play a significant role as fully recognised "legal entities". More humorous is Douglas Adams’ The Hitchhiker's Guide to the Galaxy series of picaresque novels, in which dolphins are the second most intelligent creatures on Earth (after mice, followed by humans) and try in vain to warn humans of Earth’s impending destruction
Sony VAIO PCG-7148L battery. Their story is told in So Long, and Thanks for All the Fish. Much more serious is their major role in David Brin's Uplift series. A talking Dolphin named "Howard" helps Hagbard Celine and his submarine crew fight the evil Illuminati in Robert Shea and Robert Anton Wilson's Illuminatus TrilogySony VPCW21M2E/WI battery.

Dolphins appear frequently in non-science fiction literature. In the book The Music of Dolphins by author Karen Hesse, dolphins raise a girl from the age of four until the coast guard eventually discovers her. Fantasy author Ken Grimwood wrote dolphins into his 1995 novel Into the Deep about a marine biologist struggling to crack the code of dolphin intelligence, including chapters written from a dolphinian viewpointSony VPCW21C7E battery.

Art

Dolphins are a popular artistic motif, dating back to ancient times. Examples include the Triton Fountain by Bernini and depictions of dolphins in the ruined Minoan palace at Knossos and on Minoan pottery.

Plate of dolphin sashimi.

Dolphin meat is consumed in a small number of countries world-wide, which include Japan[78] and Peru (where it is referred to as chancho marino, or "sea pork").[79] While Japan may be the best-known and most controversial example, only a very small minority of the population has ever sampled itSony VPCW12S1E/WZ battery.

Dolphin meat is dense and such a dark shade of red as to appear black. Fat is located in a layer of blubber between the meat and the skin. When dolphin meat is eaten in Japan, it is often cut into thin strips and eaten raw as sashimi, garnished with onion and either horseradish or grated garlic, much as with sashimi of whale or horse meat (basashi)Sony VPCW12S1E/W battery. When cooked, dolphin meat is cut into bite-size cubes and then batter-fried or simmered in a miso sauce with vegetables. Cooked dolphin meat has a flavor very similar to beef liver.

A crocodile is any species belonging to the family Crocodylidae (sometimes classified instead as the subfamily Crocodylinae). The term can also be used more loosely to include all extant members of the order Crocodilia: i.e. the true crocodiles, the alligators and caimans (family Alligatoridae) and the gharials (family Gavialidae) Sony VAIO PCG-8131M battery, as well as the Crocodylomorpha, which include prehistoric crocodile relatives and ancestors.

Member species of the family Crocodylidae are large aquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. Crocodiles tend to congregate in freshwater habitats such as rivers, lakes, wetlands and sometimes in brackish waterSony VAIO PCG-8152M battery. They feed mostly on vertebrates - fish, reptiles, and mammals, and sometimes on invertebrates - molluscs and crustaceans, depending on species. They first appeared during the Eocene epoch, about 55 million years ago.

Etymology

The word "crocodile" comes from the Ancient Greek κροκόδιλος (crocodilos), "lizard," used in the phrase ho krokódilos ho potamós, "the lizard of the (Nile) river".

There are several variant Greek forms of the word attested, including the later form κροκόδειλος (crocodeilos) Sony VAIO PCG-31311M batteryfound cited in many English reference works.[3] In the Koine Greek of Roman times, crocodilos and crocodeilos would have been pronounced identically, and either or both may be the source of the Latinized form crocodīlus used by the ancient Romans.

Crocodilos or crocodeilos is a compound of krokè ("pebbles"), and drilos/dreilos ("worm"). It is ascribed to Herodotus, supposedly to describe the basking habits of the Egyptian crocodile.[4] However the word drilos is only attested as a colloquial term for "penis".Sony VAIO PCG-31111M battery The meaning of krokè is explained as describing the skin texture of lizards (or crocodiles) in most sources,[citation needed] but is alternately claimed to refer to a supposed habit of (lizards or crocodiles) basking on pebbly ground.

The form crocodrillus is attested in Medieval Latin.[4] It is not clear whether this is a medieval corruption or derives from alternate Greco-Latin forms (late Greek corcodrillos and corcodrillion are attested) Sony VAIO PCG-8112M battery.

A (further) corrupted form cocodrille is found in Old French and was borrowed into Middle English as cocodril(le). The Modern English form crocodile was adapted directly from the Classical Latin crocodīlus in the 16th century, replacing the earlier form.

The use of -y- in the scientific name Crocodylus (and forms derived from it) is a corruption introduced by Laurenti (1768) Sony VAIO PCG-7186M battery.

Description

Crocodiles are similar to alligators and caimans; for their common biology and differences between them, see Crocodilia.

Crocodiles, like dinosaurs, have the abdominal ribs modified into gastralia.

Crocodiles are among the more biologically complex reptiles despite their prehistoric look. Unlike other reptiles, a crocodile has a cerebral cortex, a four-chambered heart,and the functional equivalent of a diaphragmSony VAIO PCG-7171M battery, by incorporating muscles used for aquatic locomotion into respiration (e.g. m. diaphragmaticus);[6] Its external morphology, on the other hand, is a sign of its aquatic and predatory lifestyle.

A crocodile’s physical traits allow it to be a successful predator. Its streamlined body enables it to swim swiftly. It also tucks its feet to the side while swimming, which makes it faster by decreasing water resistance. Its webbed feet, though not used to propel the animal through the waterSony VAIO PCG-9Z1M battery, allow it to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallower water where the animal sometimes moves around by walking.

Crocodiles have a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water. The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence. Like other archosaursSony VAIO PCG-5S1M battery, crocodilians are diapsid, although their post-temporal fenestrae are reduced. The walls of the braincase are bony, but lack supratemporal and postfrontal bones.[7] Their tongues are not free, but held in place by a membrane which limits movement; as a result, crocodiles are unable to stick out their tongues. Sony VAIO PCG-5P1M battery

Crocodilian scales have pores believed to be sensory in function, analogous to the lateral line in fishes. They are particularly seen on their upper and lower jaws. Another possibility is they are secretory, as they produce an oily substance that appears to flush mud off.[7]

Crocodiles are very fast over short distances, even out of water. Since they feed by grabbing and holding onto their preySony VAIO PCG-5N2M battery, they have evolved sharp teeth for tearing and holding onto flesh, and powerful muscles to close the jaws and hold them shut. These jaws can bite down with immense force, by far the strongest bite of any animal. The pressure of the crocodile's bite is more than 5,000 pounds per square inch (30,000 kPa),[9] compared to just 335 pounds per square inch (2,300 kPa) for a RottweilerSony VAIO PCG-3C2M battery, 400 pounds per square inch (2,800 kPa) for a large great white shark, 800 pounds per square inch (6,000 kPa) to 1,000 pounds per square inch (7,000 kPa) for a hyena, or 2,000 pounds per square inch (10,000 kPa) for a large alligator[citation needed]. The jaws are opened, however, by a very weak set of muscles. Crocodiles can thus be subdued for study or transport by taping their jaws or holding their jaws shut with large rubber bands cut from automobile inner tubesSony VAIO PCG-8161M battery. They have limited lateral (side-to-side) neck movement.

Biology and behavior

Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they have a very slow metabolism, so they can survive long periods without food. Despite their appearance of being slow, crocodiles are top predators in their environment, and various species have been observed attacking and killing sharks. Sony VAIO PCG-8141M battery

Herodotus claimed Nile crocodiles had a symbiotic relationship with certain birds, such as the Egyptian plover, which enter the crocodile's mouth and pick leeches feeding on the crocodile's blood; with no evidence of this interaction actually occurring in any crocodile species, it is most likely mythical or allegorical fiction. Sony VAIO PCG-3J1M battery

Many large crocodilians swallow stones (called gastroliths or stomach stones) which may act as ballast to balance their bodies or assist in crushing food,[7] similar to grit in birds.

Salt glands are present in the tongues of most crocodylids and they have a pore opening on the surface of the tongue. They appear to be similar to those in marine turtles; they seem to be absent in Alligatoridae. Sony VAIO PCG-3H1M battery

Crocodilians can produce sounds during distress and in aggressive displays. They can also hear well, but their tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.[7]

A crocodile farm in Mexico

Crocodiles eat fish, birds, mammals and occasionally smaller crocodiles.

Crocodiles are protected in many parts of the world, but they also are farmed commercially. Their hides are tanned and used to make leather goods such as shoes and handbagsSony VAIO PCG-3F1M battery; crocodile meat is also considered a delicacy. The most commonly farmed species are the saltwater and Nile crocodiles, while a hybrid of the saltwater and the rare Siamese crocodile is also bred in Asian farms. Farming has resulted in an increase in the saltwater crocodile population in Australia, as eggs are usually harvested from the wild, so landowners have an incentive to conserve their habitat
Sony VAIO PCG-3C1M battery.

Distribution of crocodiles

Crocodiles are more closely related to birds and dinosaurs than to most animals classified as reptiles, the three being included in the group Archosauria ('ruling reptiles'). See Crocodilia for more information.

Crocodile embryos do not have sex chromosomes, and unlike humans, sex is not determined genetically. Sex is determined by temperature, with males produced at around 31.6 °C (89 °F), and females produced at slightly lower and higher temperaturesSony VAIO PCG-9Z2L battery. The average incubation period is around 80 days, and also is dependent on temperature.[12]

Crocodiles may possess a form of homing instinct. Three rogue saltwater crocodiles were relocated 400 kilometres by helicopter in northern Australia, but had returned to their original locations within three weeks, based on data obtained from tracking devices attached to the reptiles. Sony VAIO PCG-9Z1L battery

The land speed record for a crocodile is 17 km/h (11 mph) measured in a galloping Australian freshwater crocodile.[14] Maximum speed varies from species to species. Certain species can indeed gallop, including Cuban crocodiles, New Guinea crocodiles, African dwarf crocodiles, and even small Nile crocodilesSony VAIO PCG-9131L battery. The fastest means by which most species can move is a kind of "belly run", where the body moves in a snake-like fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of 10 or 11 km/h (around 7 mph) when they "belly run", and often faster if slipping down muddy riverbanks. Another form of locomotion is the "high walk", where the body is raised clear of the groundSony VAIO PCG-8161L battery.

Siamese crocodile sleeping with its mouth open to pant

Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may even pant like a dog.[15]

The BBC TV[16] reported thee Nile crocodile which has lurked a long time underwater to catch prey, has built up a large oxygen debt. When it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide from its muscles directly to its stomachSony VAIO PCG-8152L battery; the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone.

Size

A large saltwater crocodile in captivity in Australia

Size greatly varies between species, from the dwarf crocodile to the saltwater crocodile. Species of Palaeosuchus and Osteolaemus grow to an adult size of just 1 metre (3.3 ft) to 1.5 metres (4.9 ft) Sony VAIO PCG-8141L battery. Larger species can reach over 4.85 metres (15.9 ft) long and weigh well over 1,200 kilograms (2,600 lb). Crocodilians show pronounced sexual dimorphism, with males growing much larger and more rapidly than females.[7] Despite their large adult sizes, crocodiles start their lives at around 20 centimetres (7.9 in) long. The largest species of crocodile is the saltwater crocodile, found in eastern India, northern Australia, throughout South-east Asia, and in the surrounding watersSony VAIO PCG-8131L battery.

Two larger certifiable records are both of 6.2 metres (20 ft) crocodiles. The first was shot in the Mary River in the Northern Territory of Australia in 1974 by poachers, and measured by wildlife rangers.[citation needed] The second crocodile was killed in 1983 in the Fly River, Papua New Guinea. In the case of the second crocodile it was actually the skin that was measured by zoologist Jerome MontagueSony VAIO PCG-81312L battery, and as skins are known to underestimate the size of the actual animal, it is possible this crocodile was at least another 10 cm longer.[citation needed]

The largest crocodile ever held in captivity is an estuarine–Siamese hybrid named Yai (Thai: ใหญ่, meaning big) (born 10 June 1972) at the famous Samutprakarn Crocodile Farm and Zoo, Thailand. This animal measures 6 m (19.69 ft) (19 ft 8 in) in length and weighs 1114.27 kg. Sony VAIO PCG-81214L battery

Meanwhile, the longest crocodile captured alive is Lolong which was measured at 6.096 metres (20 ft 3 in) by a National Geographic team in Agusan del Sur Province, Philippines.[18]

Wildlife experts, however, argue the largest crocodile so far found in the Bhitarkanika was almost 23 feet (7.0 m) long, which could be traced from the skull preserved by the Kanika royal familySony VAIO PCG-81115L battery. The crocodile was shot near Dhamara in 1926 and later its skull was preserved by the then Kanika king. Crocodile experts estimated the animal was between 20 feet (6.1 m) and 23 feet (7.0 m) long, as the size of the skull was measured one-ninth of the total length of the body.

Age

Measuring crocodile age is unreliable, although several techniques are used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth--Sony VAIO PCG-81114L batteryeach ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons.[19] Bearing these inaccuracies in mind, the oldest crocodilians appear to be the largest species. C. porosus is estimated to live around 70 years on average, with limited evidence of some individuals exceeding 100 years. One of the oldest crocodiles recorded died in a zoo in RussiaSony VAIO PCG-81113L battery. A male freshwater crocodile at the Australia Zoo is estimated to be 130 years old. He was rescued from the wild by Bob Irwin and Steve Irwin after being shot twice by hunters. As a result of the shootings, this crocodile (known affectionately as "Mr. Freshy") has lost his right eye. Sony VAIO PCG-7142L battery

Skin

Crocodiles have smooth skin on their bellies and sides, while their dorsal surfaces are armoured with large osteoderms. The armoured skin has scales and is thick and rugged, providing some protection. They are still able to absorb heat through this armour, as a network of small capillaries allow blood through the scales to absorb heatSony VAIO PCG-7141L battery.

Taxonomy of the Crocodylidae

Crocodiles and humans

Danger to humans

Main article: Crocodile attacks

Crocodile warning sign, Trinity Beach, Queensland, Australia

The larger species of crocodiles are very dangerous to humans, mainly not from their ability to run after a person, but their ability to strike before the person can react. The saltwater crocodile and Nile crocodile are the most dangerous, killing hundreds of people each year in parts of Southeast Asia and Africa. The mugger crocodile, American crocodile, American alligator and black caiman are also dangerous to humansSony VAIO PCG-71111L battery.

Crocodile products

Main article: Crocodile farm

Crocodile leather wallets from a Bangkok crocodile farm

Chiang Mai crocodile leather belt

Crocodile leather can be made into goods such as wallets, briefcases, purses, handbags, belts, hats, and shoes.

Crocodile meat is consumed in some countries, such as Australia, Ethiopia, Thailand, South Africa and also Cuba (in pickled form); it can also be found in specialty restaurants in some parts of the United StatesSony VAIO PCG-61411L battery. The meat is white and its nutritional composition compares favourably with that of other meats.[citation needed] It tends to have a slightly higher cholesterol level than other meats. Crocodile meat has a delicate flavour; some describe it as a cross between chicken and crab.[citation needed] Cuts of meat include backstrap and tail filletSony VAIO PCG-61112L battery.

Sharks are a group of fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii), and are the sister group to the rays. However, the term "shark" has also been used for extinct members of the suborder Elasmobranchii outside the SelachimorphaSony VAIO PCG-61111L battery, such as Cladoselache and Xenacanthus. Under this broader definition, the earliest known sharks date from more than 420 million years ago.[1]

Since that time, sharks have diversified into over 400 species. They range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species of only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus)Sony VAIO PCG-5T4L battery, the largest fish in the world, which reaches approximately 12 metres (39 ft). Despite its size, the whale shark feeds only on plankton, squid, and small fish by filter feeding. Sharks are found in all seas and are common down to depths of 2,000 metres (6,600 ft). They generally do not live in freshwater although there are a few known exceptionsSony VAIO PCG-5T3L battery, such as the bull shark and the river shark that can survive in both seawater and freshwater.[2] They breathe through five to seven gill slits. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They also have several sets of replaceable teeth. Sony VAIO PCG-5T2L battery

Well-known species such as the great white shark, tiger shark, blue shark, mako shark, and the hammerhead shark are apex predators—organisms at the top of their underwater food chain. Their predatory skill fascinates and frightens humans, even though their survival is threatened by human-related activitiesSony VAIO PCG-5S3L battery.

Etymology

Until the 16th century,[4] sharks were known to mariners as "sea dogs".[5] The etymology of the word "shark" is uncertain. One theory is that it derives from the Yucatec Maya word xok, pronounced 'shok'.[6] Evidence for this etymology comes from the OED, which notes the name "shark" first came into use after Sir John Hawkins' sailors exhibited one in London in 1569 and used the word "sharke" to refer to the large sharks of the Caribbean SeaSony VAIO PCG-5S2L battery.

An alternate etymology states that the original sense of the word was that of "predator, one who preys on others" from the German Schorck, a variant of Schurke "villain, scoundrel" (cf. card shark, loan shark, etc.), which was later applied to the fish due to its predatory behaviour. Sony VAIO PCG-5S1L battery

Anatomy

Teeth

Main article: Shark teeth

The teeth of tiger sharks are oblique and serrated to saw through flesh

Shark teeth are embedded in the gums rather than directly affixed to the jaw, and are constantly replaced throughout life. Multiple rows of replacement teeth grow in a groove on the inside of the jaw and steadily move forward in comparison to a conveyor belt; some sharks lose 30,000 or more teeth in their lifetimeSony VAIO PCG-5R2L battery. The rate of tooth replacement varies from once every 8 to 10 days to several months. In most species, teeth are replaced one at a time as opposed to the simultaneous replacement of an entire row, which is observed in the cookiecutter shark.[8]

Tooth shape depends on the shark's diet: those that feed on mollusks and crustaceans have dense and flattened teeth used for crushing, those that feed on fish have needle-like teeth for grippingSony VAIO PCG-5R1L battery, and those that feed on larger prey such as mammals have pointed lower teeth for gripping and triangular upper teeth with serrated edges for cutting. The teeth of plankton-feeders such as the basking shark are small and non-functional.[9]

Skeleton

Shark skeletons are very different from those of bony fish and terrestrial vertebrates. Sharks and other cartilaginous fish (skates and rays) have skeletons made of cartilage and connective tissue. Cartilage is flexible and durableSony VAIO PCG-5P4L battery, yet is about half the normal density of bone. This reduces the skeleton’s weight, saving energy.[10] Because sharks do not have rib cages, they can easily be crushed under their own weight on land.[11]

Jaw

Jaws of sharks, like those of rays and skates, are not attached to the cranium. The jaw's surface (in comparison to the shark's vertebrae and gill arches) needs extra support due to its heavy exposure to physical stress and its need for strengthSony VAIO PCG-5P2L battery. It has a layer of tiny hexagonal plates called "tesserae", which are crystal blocks of calcium salts arranged as a mosaic.[12] This gives these areas much of the same strength found in the bony tissue found in other animals.

Generally sharks have only one layer of tesserae, but the jaws of large specimens, such as the bull shark, tiger shark, and the great white shark, have two to three layers or more, depending on body size. The jaws of a large great white shark may have up to five layers. Sony VAIO PCG-5N4L battery In the rostrum (snout), the cartilage can be spongy and flexible to absorb the power of impacts.

Fins

Fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling the horny keratin in hair and feathers.[13] Most sharks have eight fins. Sharks can only drift away from objects directly in front of them because their fins do not allow them to move in the tail-first direction. Sony VAIO PCG-5N2L battery

Dermal denticles

Main article: Dermal denticle

Unlike bony fish, sharks have a complex dermal corset made of flexible collagenous fibers and arranged as a helical network surrounding their body. This works as an outer skeleton, providing attachment for their swimming muscles and thus saving energy.[14] Their dermal teeth give them hydrodynamic advantages as they reduce turbulence when swimming. Sony VAIO PCG-51513L battery

Tails

Tails provide thrust, making speed and acceleration dependent on tail shape. Caudal fin shapes vary considerably between shark species, due to their evolution in separate environments. Sharks possess a heterocercal caudal fin in which the dorsal portion is usually noticeably larger than the ventral portionSony VAIO PCG-51511L battery. This is because the shark's vertebral column extends into that dorsal portion, providing a greater surface area for muscle attachment. This allows more efficient locomotion among these negatively buoyant cartilaginous fish. By contrast, most bony fish possess a homocercal caudal fin.[15]

Tiger sharks have a large upper lobe, which allows for slow cruising and sudden bursts of speed. The tiger shark must be able to twist and turn in the water easily when hunting to support its varied diet, whereas the porbeagle sharkSony VAIO PCG-51412L battery, which hunts schooling fish such as mackerel and herring, has a large lower lobe to help it keep pace with its fast-swimming prey.[16] Other tail adaptations help sharks catch prey more directly, such as the thresher shark's usage of its powerful, elongated upper lobe to stun fish and squidSony VAIO PCG-51411L battery.

Physiology

Buoyancy

Unlike bony fish, sharks do not have gas-filled swim bladders for buoyancy. Instead, sharks rely on a large liver filled with oil that contains squalene, and their cartilage, which is about half the normal density of bone.[14] Their liver constitutes up to 30% of their total body mass.[17] The liver's effectiveness is limited, so sharks employ dynamic lift to maintain depth when not swimmingSony VAIO PCG-51312L battery. Sand tiger sharks store air in their stomachs, using it as a form of swim bladder. Most sharks need to constantly swim in order to breathe and cannot sleep very long without sinking (if at all). However, certain species, like the nurse shark, are capable of pumping water across their gills, allowing them to rest on the ocean bottom. Sony VAIO PCG-51311L battery

Some sharks, if inverted or stroked on the nose, enter a natural state of tonic immobility. Researchers use this condition to handle sharks safely.[19]

Respiration

Like other fish, sharks extract oxygen from seawater as it passes over their gills. Unlike other fish, shark gill slits are not covered, but lie in a row behind the head. A modified slit called a spiracle lies just behind the eyeSony VAIO PCG-51211L battery, which assists the shark with taking in water during respiration and plays a major role in bottom–dwelling sharks. Spiracles are reduced or missing in active pelagic sharks.[9] While the shark is moving, water passes through the mouth and over the gills in a process known as "ram ventilation". While at rest, most sharks pump water over their gills to ensure a constant supply of oxygenated waterSony VAIO PCG-41112L battery. A small number of species have lost the ability to pump water through their gills and must swim without rest. These species are obligate ram ventilators and would presumably asphyxiate if unable to move. Obligate ram ventilation is also true of some pelagic bony fish species. Sony VAIO PCG-3A4L battery

The respiration and circulation process begins when deoxygenated blood travels to the shark's two-chambered heart. Here the shark pumps blood to its gills via the ventral aorta artery where it branches into afferent brachial arteries. Reoxygenation takes place in the gills and the reoxygenated blood flows into the efferent brachial arteriesSony VAIO PCG-3A3L battery, which come together to form the dorsal aorta. The blood flows from the dorsal aorta throughout the body. The deoxygenated blood from the body then flows through the posterior cardinal veins and enters the posterior cardinal sinuses. From there blood enters the heart ventricle and the cycle repeats. Sony VAIO PCG-3A2L battery

Thermoregulation

Most sharks are "cold-blooded" or, more precisely, poikilothermic, meaning that their internal body temperature matches that of their ambient environment. Members of the family Lamnidae (such as the shortfin mako shark and the great white shark) are homeothermic and maintain a higher body temperature than the surrounding waterSony VAIO PCG-3A1L battery. In these sharks, a strip of aerobic red muscle located near the center of the body generates the heat, which the body retains via a countercurrent exchange mechanism by a system of blood vessels called the rete mirabile ("miraculous net"). The common thresher shark has a similar mechanism for maintaining an elevated body temperature, which is thought to have evolved independently[not in citation given]. Sony VAIO PCG-394L battery

Osmoregulation

In contrast to bony fish, with the exception of the coelacanth,[23] the blood and other tissue of sharks and Chondrichthyes is generally isotonic to their marine environments because of the high concentration of urea and trimethylamine N-oxide (TMAO), allowing them to be in osmotic balance with the seawater. This adaptation prevents most sharks from surviving in freshwaterSony VAIO PCG-393L battery, and they are therefore confined to marine environments. A few exceptions exist, such as the bull shark, which has developed a way to change its kidney function to excrete large amounts of urea.[17] When a shark dies, the urea is broken down to ammonia by bacteria, causing the dead body to gradually smell strongly of ammoniaSony VAIO PCG-391L battery.

Digestion

Digestion can take a long time. The food moves from the mouth to a J-shaped stomach, where it is stored and initial digestion occurs.[26] Unwanted items may never get past the stomach, and instead the shark either vomits or turns its stomachs inside out and ejects unwanted items from its mouthSony VAIO PCG-384L battery.

One of the biggest differences between the digestive systems of sharks and mammals is that sharks have much shorter intestines. This short length is achieved by the spiral valve with multiple turns within a single short section instead of a long tube-like intestine. The valve provides a long surface area, requiring food to circulate inside the short gut until fully digested, when remaining waste products pass into the cloaca. Sony VAIO PCG-383L battery

Senses

Smell

The shape of the hammerhead shark's head may enhance olfaction by spacing the nostrils further apart.

Sharks have keen olfactory senses, located in the short duct (which is not fused, unlike bony fish) between the anterior and posterior nasal openings, with some species able to detect as little as one part per million of blood in seawater.Sony VAIO PCG-382L battery

Sharks have the ability to determine the direction of a given scent based on the timing of scent detection in each nostril.[28] This is similar to the method mammals use to determine direction of sound.

They are more attracted to the chemicals found in the intestines of many species, and as a result often linger near or in sewage outfalls. Some species, such as nurse sharks, have external barbels that greatly increase their ability to sense preySony VAIO PCG-381L battery.

Sight

Shark eyes are similar to the eyes of other vertebrates, including similar lenses, corneas and retinas, though their eyesight is well adapted to the marine environment with the help of a tissue called tapetum lucidum. This means that sharks can contract and dilate their pupils, like humans, something no teleost fish can doSony VAIO PCG-7185L battery. This tissue is behind the retina and reflects light back to it, thereby increasing visibility in the dark waters. The effectiveness of the tissue varies, with some sharks having stronger nocturnal adaptations. Sharks have eyelids, but they do not blink because the surrounding water cleans their eyes. To protect their eyes some species have nictitating membranesSony VAIO PCG-7184L battery. This membrane covers the eyes while hunting and when the shark is being attacked. However, some species, including the great white shark (Carcharodon carcharias), do not have this membrane, but instead roll their eyes backwards to protect them when striking prey. The importance of sight in shark hunting behavior is debatedSony VAIO PCG-7183L battery. Some believe that electro- and chemoreception are more significant, while others point to the nictating membrane as evidence that sight is important. Presumably, the shark would not protect its eyes were they unimportant. The use of sight probably varies with species and water conditions. The shark's field of vision can swap between monocular and stereoscopic at any time. Sony VAIO PCG-7182L battery A micro-spectrophotometry study of 17 species of shark found 10 had only rod photoreceptors and no cone cells in their retinas giving them good night vision while making them colorblind. The remaining seven species had in addition to rods a single type of cone photoreceptor sensitive to green and, seeing only in shades of grey and green, are believed to be effectively colorblindSony VAIO PCG-7181L battery. The study indicates that an object's contrast against the background, rather than colour, may be more important for object detection.

Hearing

Although it is hard to test sharks' hearing, they may have a sharp sense of hearing and can possibly hear prey many miles away.[33] A small opening on each side of their heads (not the spiracle) leads directly into the inner ear through a thin channelSony VAIO PCG-7174L battery. The lateral line shows a similar arrangement, and is open to the environment via a series of openings called lateral line pores. This is a reminder of the common origin of these two vibration- and sound-detecting organs that are grouped together as the acoustico-lateralis system. In bony fish and tetrapods the external opening into the inner ear has been lostSony VAIO PCG-7173L battery.

Electroreception

Main article: Electroreception

Electromagnetic field receptors (ampullae of Lorenzini) and motion detecting canals in the head of a shark

The ampullae of Lorenzini are the electroreceptor organs. They number in the hundreds to thousands. Sharks use the ampullae of Lorenzini to detect the electromagnetic fields that all living things produce.[34] This helps sharks (particularly the hammerhead shark) find preySony VAIO PCG-7172L battery. The shark has the greatest electrical sensitivity of any animal. Sharks find prey hidden in sand by detecting the electric fields they produce. Ocean currents moving in the magnetic field of the Earth also generate electric fields that sharks can use for orientation and possibly navigation.[35]

Lateral line

Main article: Lateral line

This system is found in most fish, including sharks. It detects motion or vibrations in water. The shark can sense frequencies in the range of 25 to 50 HzSony VAIO PCG-7171L battery.

Life history

The claspers of male spotted wobbegong

Shark lifespans vary by species. Most live 20 to 30 years. The spiny dogfish has the longest lifespan at more than 100 years.[37] Whale sharks (Rhincodon typus) may also live over 100 years.[38]

Reproduction

Unlike most bony fish, sharks are K-selected reproducers, meaning that they produce a small number of well-developed young as opposed to a large number of poorly developed young. Fecundity in sharks ranges from 2 to over 100 young per reproductive cycle. Sony VAIO PCG-7162L battery Sharks mature slowly relative to many other fish. For example, lemon sharks reach sexual maturity at around age 13–15.

Sexual

Sharks practice internal fertilization. The posterior part of a male shark's pelvic fins are modified into a pair of intromittent organs called claspers, analogous to a mammalian penis, of which one is used to deliver sperm into the female. Sony VAIO PCG-7161L battery

Mating has rarely been observed in sharks. The smaller catsharks often mate with the male curling around the female. In less flexible species the two sharks swim parallel to each other while the male inserts a clasper into the female's oviduct. Females in many of the larger species have bite marks that appear to be a result of a male grasping them to maintain position during mating. The bite marks may also come from courtship behaviorSony VAIO PCG-7154L battery: the male may bite the female to show his interest. In some species, females have evolved thicker skin to withstand these bites.

Asexual

There are two documented cases in which a female shark who has not been in contact with a male has conceived a pup on her own through parthenogenesis. The details of this process are not well understood, but genetic fingerprinting showed that the pups had no paternal genetic contribution, ruling out sperm storageSony VAIO PCG-7153L battery. The extent of this behavior in the wild is unknown, as is whether other species have this capability. Mammals are now the only major vertebrate group in which asexual reproduction has not been observed.

Scientists assert that asexual reproduction in the wild is rare, and probably a last-ditch effort to reproduce when a mate is not presentSony VAIO PCG-7152L battery. Asexual reproduction diminishes genetic diversity, which helps build defenses against threats to the species. Species that rely solely on it risk extinction. Asexual reproduction may have contributed to the blue shark's decline off the Irish coast.[44]

Brooding

Sharks display three ways to bear their young, varying by species, oviparity, viviparity and ovoviviparity. Sony VAIO PCG-7151L battery

The spiral egg case of a Port Jackson shark

Ovoviviparity

Most sharks are ovoviviparous, meaning that the eggs hatch in the oviduct within the mother's body and that the egg's yolk and fluids secreted by glands in the walls of the oviduct nourishes the embryos. The young continue to be nourished by the remnants of the yolk and the oviduct's fluids. As in viviparity, the young are born alive and fully functional
Sony VAIO PCG-7148L battery. Lamniforme sharks practice oophagy, where the first embryos to hatch eat the remaining eggs. Grey nurse shark pups intrauterine cannibalistically take this a step further and consume other developing embryos. The survival strategy for ovoviviparous species is to brood the young to a comparatively large size before birth. The whale shark is now classified as ovoviviparous rather than oviparousSony VPCW21M2E/WI battery, because extrauterine eggs are now thought to have been aborted. Most ovoviviparous sharks give birth in sheltered areas, including bays, river mouths and shallow reefs. They choose such areas for protection from predators (mainly other sharks) and the abundance of food. Dogfish have the longest known gestation period of any shark, at 18 to 24 monthsSony VPCW21C7E battery. Basking sharks and frilled sharks appear to have even longer gestation periods, but accurate data are lacking.[45]

Oviparity

Some species are oviparous like most other fish, laying their eggs in the water. In most oviparous shark species, an egg case with the consistency of leather protects the developing embryo(s). These cases may be corkscrewed into crevices for protection. Once empty, the egg case is known as the mermaid's purse, and can wash up on shore. Oviparous sharks include the horn shark, catshark, Port Jackson shark, and swellsharkSony VPCW12S1E/WZ battery.

Viviparity

Finally some sharks maintain a placental link to the developing young, this method is called viviparity. This is more analogous to mammalian gestation than that of other fishes. The young are born alive and fully functional. Hammerheads, the requiem sharks (such as the bull and blue sharks), and smoothhounds are viviparousSony VPCW12S1E/W battery.

Behavior

The classic view describes a solitary hunter, ranging the oceans in search of food. However, this applies to only a few species. Most live far more sedentary, benthic lives. Even solitary sharks meet for breeding or at rich hunting grounds, which may lead them to cover thousands of miles in a year.[47] Shark migration patterns may be even more complex than in birds, with many sharks covering entire ocean basinsSony VPCW12S1E/T battery.

Sharks can be highly social, remaining in large schools. Sometimes more than 100 scalloped hammerheads congregate around seamounts and islands, e.g., in the Gulf of California.[17] Cross-species social hierarchies exist. For example, oceanic whitetip sharks dominate silky sharks of comparable size during feeding. Sony VPCW12S1E/P battery

When approached too closely some sharks perform a threat display. This usually consists of exaggerated swimming movements, and can vary in intensity according to the threat level.[48]

Speed

In general, sharks swim ("cruise") at an average speed of 8 kilometres per hour (5.0 mph) but when feeding or attacking, the average shark can reach speeds upwards of 19 kilometres per hour (12 mph) Sony VPCW11S1E/W battery. The shortfin mako shark, the fastest shark and one of the fastest fish, can burst at speeds up to 50 kilometres per hour (31 mph).[49] The great white shark is also capable of speed bursts. These exceptions may be due to the warm-blooded, or homeothermic, nature of these sharks' physiology.

Intelligence

Sharks possess brain-to-body mass ratios that are similar to mammals and birds,[50] and have exhibited apparent curiosity and behavior resembling play in the wildSony VPCW11S1E/T battery.

Sleep

Some sharks can lie on the bottom while actively pumping water over their gills, but their eyes remain open and actively follow divers.[53] When a shark is resting, it does not use its nares, but rather its spiracles. If a shark tried to use its nares while resting on the ocean floor, it would "inhale" sand rather than waterSony VPCW11S1E/P battery. Many scientists believe this is one of the reasons sharks have spiracles. The spiny dogfish's spinal cord, rather than its brain, coordinates swimming, so spiny dogfish can continue to swim while sleeping.[53] It is also possible that sharks sleep in a manner similar to dolphins,[53] one cerebral hemisphere at a time, thus maintaining some consciousness and cerebral activity at all timesSony VPCYA1S1E/B battery.

Ecology

Feeding

This section is about shark feeding. For the sport of shark feeding, see Shark baiting.

Like many sharks, the great white shark is an apex predator in its environment.

Most sharks are carnivorous.[54] Basking sharks, whale sharks, and megamouth sharks sharks have independently evolved different strategies for filter feeding plankton: basking sharks practice ram feeding, whale sharks use suction to take in plankton and small fishesSony VPCYA1V9E/B battery, and megamouth sharks make suction feeding more efficient by using the luminescent tissue inside of their mouths to attract prey in the deep ocean. This type of feeding requires gill rakers—long, slender filaments that form a very efficient sieve—analogous to the baleen plates of the great whales. The shark traps the plankton in these filaments and swallows from time to time in huge mouthfulsSony VPCY21S1E/SI battery. Teeth in these species are comparatively small because they are not needed for feeding.[54]

Other highly specialized feeders include cookiecutter sharks, which feed on flesh sliced out of other larger fish and marine mammals. Cookiecutter teeth are enormous compared to the animal's size. The lower teeth are particularly sharp. Although they have never been observed feedingSony VPCY21S1E/L battery, they are believed to latch onto their prey and use their thick lips to make a seal, twisting their bodies to rip off flesh.[17]

Some seabed–dwelling species are highly effective ambush predators. Angel sharks and wobbegongs use camouflage to lie in wait and suck prey into their mouths.[55] Many benthic sharks feed solely on crustaceans which they crush with their flat molariform teethSony VPCY21S1E/G battery.

Other sharks feed on squid or fish, which they swallow whole. The viper dogfish has teeth it can point outwards to strike and capture prey that it then swallows intact. The great white and other large predators either swallow small prey whole or take huge bites out of large animals. Thresher sharks use their long tails to stun shoaling fishes, and sawsharks either stir prey from the seabed or slash at swimming prey with their tooth-studded rostraSony VPCY11S1E/S battery.

Many sharks, including the whitetip reef shark are cooperative feeders and hunt in packs to herd and capture elusive prey. These social sharks are often migratory, traveling huge distances around ocean basins in large schools. These migrations may be partly necessary to find new food sources. Sony VPCY11S1E battery

Range and habitat

Sharks are found in all seas. They generally do not live in fresh water, with a few exceptions such as the bull shark and the river shark which can swim both in seawater and freshwater.[57] Sharks are common down to depths of 2,000 metres (7,000 ft), and some live even deeper, but they are almost entirely absent below 3,000 metres (10,000 ft). The deepest confirmed report of a shark is a Portuguese dogfish at 3,700 metres (12,100 ft) Sony VPCZ11X9E/B battery.

Relationship with humans

Attacks

A sign warning about the presence of sharks in Salt Rock, South Africa

Snorkeler swims near blacktip reef shark. In rare circumstances involving poor visibility, blacktips may bite a human, mistaking it for prey. Under normal conditions they are harmless and shy.

Main article: Shark attack

In 2006 the International Shark Attack File (ISAF) undertook an investigation into 96 alleged shark attacksSony VPCY11S1E battery, confirming 62 of them as unprovoked attacks and 16 as provoked attacks. The average number of fatalities worldwide per year between 2001 and 2006 from unprovoked shark attacks is 4.3.[59]

Contrary to popular belief, only a few sharks are dangerous to humans. Out of more than 360 species, only four have been involved in a significant number of fatal, unprovoked attacks on humans: the great white, oceanic whitetip, tiger, and bull sharks. Sony VPCZ11X9E/B battery These sharks are large, powerful predators, and may sometimes attack and kill people. Despite being responsible for attacks on humans they have all been filmed without using a protective cage.[62]

The perception of sharks as dangerous animals has been popularized by publicity given to a few isolated unprovoked attacks, such as the Jersey Shore shark attacks of 1916Sony VPCZ11Z9E/B battery, and through popular fictional works about shark attacks, such as the Jaws film series. Jaws author Peter Benchley, as well as Jaws director Steven Spielberg later attempted to dispel the image of sharks as man-eating monsters.[63]

In captivity

A whale shark in Georgia Aquarium

Main article: Sharks in captivity

Until recently only a few benthic species of shark, such as hornsharks, leopard sharks and catsharks had survived in aquarium conditions for a year or moreSony VPCZ12M9E/B battery. This gave rise to the belief that sharks, as well as being difficult to capture and transport, were difficult to care for. More knowledge has led to more species (including the large pelagic sharks) living far longer in captivity. At the same time, safer transportation techniques have enabled long distance movement.[64] One shark that never had been successfully held in captivity for long was the great whiteSony VPCZ12X9E/X battery. But in September 2004 the Monterey Bay Aquarium successfully kept a young female for 198 days before releasing her.

Most species are not suitable for home aquaria and not every species sold by pet stores are appropriate. Some species can flourish in home saltwater aquaria.[65] Uninformed or unscrupulous dealers sometimes sell juvenile sharks like the nurse sharkSony VPCZ12Z9E/X battery, which upon reaching adulthood is far too large for typical home aquaria.[65] Public aquaria generally do not accept donated specimens that have outgrown their housing. Some owners have been tempted to release them.[65] Species appropriate to home aquaria represent considerable spatial and financial investments as they generally approach adult lengths of 3 feet and can live up to 25 years. Sony VPCZ13M9E/B battery

In Hawaii

Sharks figure prominently in Hawaiian mythology. Stories tell of men with shark jaws on their back who could change between shark and human form. A common theme was that a shark-man would warn beach-goers of sharks in the waters. The beach-goers would laugh and ignore the warnings and get eaten by the shark-man who warned themSony VPCZ13M9E/X battery. Hawaiian mythology also includes many shark gods. Among a fishing people, the most popular of all aumakua, or deified ancestor guardians, are shark aumakua. Kamaku describes in detail how to offer a corpse to become a shark. The body transforms gradually until the kahuna can point the awe-struck family to the markings on the shark's body that correspond to the clothing in which the beloved's body had been wrappedSony VPCZ13V9E battery. Such a shark aumakua becomes the family pet, receiving food, and driving fish into the family net and warding off danger. Like all aumakua it had evil uses such as helping kill enemies. The ruling chiefs typically forbade such sorcery. Many Native Hawaiian families claim such an aumakua, who is known by name to the whole community. Sony VPCZ13V9E/X battery

Kamohoali'i is the best known and revered of the shark gods, he was the older and favored brother of Pele,[67] and helped and journeyed with her to Hawaii. He was able to assume all human and fish forms. A summit cliff on the crater of Kilauea is one of his most sacred spots. At one point he had a heiau (temple or shrine) dedicated to him on every piece of land that jutted into the ocean on the island of Moloka'iSony VPCZ13Z9E/X battery. Kamohoali'i was an ancestral god, not a human who became a shark and banned the eating of humans after eating one herself. In Fijian mytholog, Dakuwanga was a shark god who was the eater of lost souls.

Popular misconceptions

A popular myth is that sharks are immune to disease and cancer; this is not scientifically supported. Sharks may get cancer. Both diseases and parasites affect sharksSony VPCZ21M9E battery. The evidence that sharks are at least resistant to cancer and disease is mostly anecdotal and there have been few, if any, scientific or statistical studies that show sharks to have heightened immunity to disease.[72] Other apparently false claims are that fins prevent cancer[73] and treat osteoarthritis.[74] No scientific proof supports these claims; at least one study has shown shark cartilage of no value in cancer treatment. Sony VPCZ21Q9E battery

Conservation

Further information: Shark sanctuary

The value of shark fins for shark fin soup has led to an increase in shark catches. Usually only the fins are taken, while the rest of the shark is discarded, usually into the sea.

Fishery

The annual shark catch has increased rapidly over the last 50 years.

It is estimated that 100 million sharks are killed by people every year, due to commercial and recreational fishing. Sharks are a common seafood in many places, including Japan and Australia. In the Australian state of VictoriaSony VPCZ21V9E battery, shark is the most commonly used fish in fish and chips, in which fillets are battered and deep-fried or crumbed and grilled. In fish and chip shops, shark is called flake. In India, small sharks or baby sharks (called sora in Tamil language, Telugu language) are sold in local markets. Since the flesh is not developed, cooking the flesh breaks it into powder, which is then fried in oil and spices (called sora puttu/sora poratu) Sony VPCEH3T9E battery. The soft bones can be easily chewed. They are considered a delicacy in coastal Tamil Nadu. Icelanders ferment Greenland sharks to produce hákarl, which is widely regarded as a national dish.[citation needed]

A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne‘ohe Bay, Oahu in 1966

Sharks are often killed for shark fin soup. Fishermen capture live sharks, fin them, and dump the finless animal back into the water. Shark finning involves removing the fin with a hot metal blade. Sony VPCEH3N6E battery The resulting immobile shark soon dies from suffocation or predators.[78] Shark fin has become a major trade within black markets all over the world. Fins sell for about $300/lb in 2009.[79] Poachers illegally fin millions each year. Few governments enforce laws that protect them.[citation needed] In 2010 Hawaii became the first U.S. state to prohibit the possession, sale, trade or distribution of shark fins. Sony VPCEH3N1E battery

Shark fin soup is a status symbol in Asian countries, and is considered healthy and full of nutrients. Sharks are also killed for meat. European diners consume dogfishes, smoothhounds, catsharks, makos, porbeagle and also skates and rays.[81] However, the U.S. FDA lists sharks as one of four fish (with swordfish, king mackerel, and tilefish) whose high mercury content is hazardous to children and pregnant womenSony VPCEH3D0E battery.

Sharks generally reach sexual maturity only after many years and produce few offspring in comparison to other harvested fish. Harvesting sharks before they reproduce severely impacts future populations.

The majority of shark fisheries have little monitoring or management. The rise in demand for shark products increases pressure on fisheries. Sony VPCEH3B1E battery Major declines in shark stocks have been recorded—some species have been depleted by over 90% over the past 20–30 years with population declines of 70% not unusual.[82] Many governments and the UN have acknowledged the need for shark fisheries management, but little progress has been made due to their low economic value, the small volumes of products produced and sharks' poor public image. Sony VPCEH2Z1E battery

Other threats

Other threats include habitat alteration, damage and loss from coastal development, pollution and the impact of fisheries on the seabed and prey species.[83] The 2007 documentary, Sharkwater exposed how sharks are being hunted to extinction.[84]

Protection

In 1991 South Africa was the first country in the world to declare Great White sharks a legally protected species. Sony VPCEH2S9E battery

Intending to ban the practice of shark finning while at sea, the United States Congress passed the Shark Finning Prohibition Act in 2000.[86] Two years later the Act saw its first legal challenge in United States v. Approximately 64,695 Pounds of Shark Fins. In 2008 a Federal Appeals Court ruled that a loophole in the law allowed non-fishing vessels to purchase shark fins from fishing vessels while on the high seas. Sony VPCEH2Q1E battery Seeking to close the loophole, the Shark Conservation Act was passed by Congress in December 2010, and it was signed into law in January 2011.[88][89]

In 2009, the International Union for the Conservation of Nature (IUCN) Red List of Endangered Species named 64 species, one-third of all oceanic shark species, as being at risk of extinction due to fishing and shark finningSony VPCEH2P0E battery.

In 2010, the Convention on International Trade in Endangered Species (CITES) rejected proposals from the United States and Palau that would have required countries to strictly regulate trade in several species of scalloped hammerhead, oceanic whitetip and spiny dogfish sharks. The majority, but not the required two-thirds of voting delegatesSony VPCEH2N1E battery, approved the proposal. China, by far the world’s largest shark market, and Japan, which battles all attempts to extend the convention to marine species, led the opposition.

In 2010, Greenpeace International added the school shark, shortfin mako shark, mackerel shark, tiger shark and spiny dogfish to its seafood red list, a list of common supermarket fish that are often sourced from unsustainable fisheries.Sony VPCEH2M9E battery Advocacy group Shark Trust campaigns to limit shark fishing. Advocacy group Seafood Watch directs American consumers to not eat sharks.[95]

Evolution

A collection of Cretaceous shark teeth

Evidence for the existence of sharks dates from the Ordovician period, over 450–420 million years ago, before land vertebrates existed and before many plants had colonized the continents. Sony VPCEH2M1E battery Only scales have been recovered from the first sharks and not all paleontologists agree that these are from true sharks.[96] The oldest generally accepted shark scales are from about 420 million years ago, in the Silurian period.[96] The first sharks looked very different from modern sharks.[97] The majority of modern sharks can be traced back to around 100 million years ago. Sony VPCEH2L9E battery Most fossils are of teeth, often in large numbers. Partial skeletons and even complete fossilized remains have been discovered. Estimates suggest that sharks grow tens of thousands of teeth over a lifetime, which explains the abundant fossils. The teeth consist of easily fossilized calcium phosphate, an apatite. When a shark dies, the decomposing skeleton breaks up, scattering the apatite prismsSony VPCEH2J1E battery. Preservation requires rapid burial in bottom sediments.

Among the most ancient and primitive sharks is Cladoselache, from about 370 million years ago,[97] which has been found within Paleozoic strata in Ohio, Kentucky and Tennessee. At that point in Earth's history these rocks made up the soft bottom sediments of a large, shallow ocean, which stretched across much of North AmericaSony VPCEH2H1E battery. Cladoselache was only about 1 metre (3.3 ft) long with stiff triangular fins and slender jaws.[97] Its teeth had several pointed cusps, which wore down from use. From the small number of teeth found together, it is most likely that Cladoselache did not replace its teeth as regularly as modern sharks. Its caudal fins had a similar shape to the great white sharks and the pelagic shortfin and longfin makosSony VPCEH2F1E battery. The presence of whole fish arranged tail-first in their stomachs suggest that they were fast swimmers with great agility.

Most fossil sharks from about 300 to 150 million years ago can be assigned to one of two groups. The Xenacanthida was almost exclusive to freshwater environments. By the time this group became extinct about 220 million years ago, they had spread worldwide. The other group, the hybodontsSony VPCEH2E0E battery, appeared about 320 million years ago and lived mostly in the oceans, but also in freshwater.

Megalodon with the whale shark, great white shark, and a human for scale

Modern sharks began to appear about 100 million years ago.[98] Fossil mackerel shark teeth date to the Lower Cretaceous. One of the most recently evolved families is the hammerhead shark (family Sphyrnidae), which emerged in the Eocene. Sony VPCEH2D0E battery The oldest white shark teeth date from 60 to 65 million years ago, around the time of the extinction of the dinosaurs. In early white shark evolution there are at least two lineages: one lineage is of white sharks with coarsely serrated teeth and it probably gave rise to the modern great white shark, and another lineage is of white sharks with finely serrated teethSony VPCEH2C0E battery. These sharks attained gigantic proportions and include the extinct megatoothed shark, C. megalodon. Like most extinct sharks, C. megalodon is also primarily known from its fossil teeth and vertebrae. This giant shark reached a total length (TL) of more than 16 metres (52 ft). C. megalodon may have approached a maxima of 20.3 metres (67 ft) in total length and 103 metric tons (114 short tons) in mass. Sony VPCEH1Z1E battery Paleontological evidence suggests that this shark was an active predator of large cetaceans.

Taxonomy

Sharks belong to the superorder Selachimorpha in the subclass Elasmobranchii in the class Chondrichthyes. The Elasmobranchii also include rays and skates; the Chondrichthyes also include Chimaeras. It is currently thought that the sharks form a polyphyletic group: some sharks are more closely related to rays than they are to some other sharks.Sony VPCEH1S9E battery

The superorder Selachimorpha is divided into Galea (or Galeomorphii), and Squalea. The Galeans are the Heterodontiformes, Orectolobiformes, Lamniformes, and Carcharhiniformes. Lamnoids and Carcharhinoids are usually placed in one clade, but recent studies show the Lamnoids and Orectoloboids are a clade. Some scientists now think that Heterodontoids may be SqualeanSony VPCEH1S8E battery. The Squalea is divided into Hexanchoidei and Squalomorpha. The Hexanchoidei includes the Hexanchiformes and Chlamydoselachiformes. The Squalomorpha contains the Squaliformes and the Hypnosqualea. The Hypnosqualea may be invalid. It includes the Squatiniformes, and the Pristorajea, which may also be invalid, but includes the Pristiophoriformes and the BatoideaSony VPCEH1S1E battery.

More than 440 species of sharks split across eight orders, listed below in roughly their evolutionary relationship from ancient to modern:[106]

Hexanchiformes: Examples from this group include the cow sharks, frilled shark and even a shark that resembles a marine snake.

Squaliformes: This group includes the bramble sharks, dogfish and roughsharks, and prickly sharkSony VPCEH1S0E battery.

Pristiophoriformes: These are the sawsharks, with an elongated, toothed snout that they use for slashing their prey.

Squatiniformes: Also known as angel sharks, they are flattened sharks with a strong resemblance to stingrays and skates.

Heterodontiformes: They are generally referred to as the bullhead or horn sharks.

Orectolobiformes: They are commonly referred to as the carpet sharks, including zebra sharks, nurse sharks, wobbegongs and the whale sharkSony VPCEH1M9E battery.

Carcharhiniformes: Commonly known as groundsharks, the species include the blue, tiger, bull, grey reef, blacktip reef, Caribbean reef, blacktail reef, whitetip reef and oceanic whitetip sharks (collectively called the requiem sharks) along with the houndsharks, catsharks and hammerhead sharks. They are distinguished by an elongated snout and a nictitating membrane which protects the eyes during an attackSony VPCEH1M1E battery.

Lamniformes: They are commonly known as the mackerel sharks. They include the goblin shark, basking shark, megamouth shark, the thresher sharks, shortfin and longfin mako sharks, and great white shark. They are distinguished by their large jaws and ovoviviparous reproduction. The Lamniformes include the extinct megalodon, Carcharodon megalodonSony VPCEH1L9E battery.

Dinosaurs are a diverse group of animals of the clade Dinosauria. They first appeared during the Triassic period, approximately 230 million years ago, and became the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic (about 200 million years ago) until the end of the Cretaceous (65.5 million years ago) (Dell 1691P battery), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups at the close of the Mesozoic era. The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic, and consequently they are considered a type of dinosaur in modern classification systems.[1][2] Some birds survived the extinction event that occurred 65 million years ago, and continue the dinosaur lineage to the present day(Dell 310-6321 battery).

Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 9,000 living species, are the most diverse group of vertebrates besides perciform fish.[3] Using fossil evidence, paleontologists have identified over 500 distinct genera[4] and more than 1,000 different species of non-avian dinosaurs. (Dell 312-0068 battery) Dinosaurs are represented on every continent by both extant species and fossil remains.[6] Some are herbivorous, others carnivorous. Most dinosaurs have been bipedal, though many extinct groups included quadrupedal species, and some were able to shift between these body postures. Many species possess elaborate display structures such as horns or crests(Dell 312-0078 battery), and some prehistoric groups developed skeletal modifications such as bony armor and spines. Birds have been the planet's dominant flying vertebrate since the extinction of the pterosaurs, and evidence suggests that egg laying and nest building is a trait shared by all dinosaurs. Many prehistoric dinosaurs were large animals—the largest sauropods could reach lengths of almost 60 meters (200 feet) and were several stories tall—and while many extinct theropods were quite large, a majority evolved very small sizes(Dell 312-0079 battery), especially among birds and other advanced groups.

Although the word dinosaur means "terrible lizard," the name is somewhat misleading, as dinosaurs are not lizards. Rather, they represent a separate group of reptiles with a distinct upright posture not found in lizards. Through the first half of the 20th century, before birds were recognized to be dinosaurs(Dell 312-0305 battery), most of the scientific community believed dinosaurs were sluggish and cold-blooded. Most research conducted since the 1970s, however, has indicated that ancient dinosaurs, particularly the carnivorous groups, were active animals with elevated metabolisms and numerous adaptations for social interaction.

Since the first dinosaur fossils were recognized in the early 19th century(Dell 312-0326 battery), mounted fossil dinosaur skeletons or replicas have been major attractions at museums around the world, and dinosaurs have become a part of world culture. Their diversity, the large sizes of some groups, and their seemingly monstrous and fantastic nature have captured the interest and imagination of the general public for over a century. They have been featured in best-selling books and films such as Jurassic Park(Dell 312-0518 battery), and new discoveries are regularly covered by the media.

Etymology

The taxon Dinosauria was formally named in 1842 by paleontologist Sir Richard Owen, who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were then being recognized in England and around the world.[7]:103 The term is derived from the Greek words δεινός (deinos, meaning "terrible," "potent," or "fearfully great")(Dell 312-0566 battery) and σαῦρος (sauros, meaning "lizard" or "reptile").[7]:103[8] Though the taxonomic name has often been interpreted as a reference to dinosaurs' teeth, claws, and other fearsome characteristics, Owen intended it merely to evoke their size and majesty.[9]

Definition

Triceratops horridus skeleton, American Museum of Natural History

Under phylogenetic taxonomy, dinosaurs are usually defined as the group consisting of "Triceratops, Neornithes [modern birds], their most recent common ancestor, and all descendants".(Dell 312-0585 battery)It has also been suggested that Dinosauria be defined with respect to the most recent common ancestor of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria.[11] Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia"(Dell 312-0831 battery), encompassing theropods (mostly bipedal carnivores and birds), ankylosaurians (armored herbivorous quadrupeds), stegosaurians (plated herbivorous quadrupeds), ceratopsians (herbivorous quadrupeds with horns and frills), ornithopods (bipedal or quadrupedal herbivores including "duck-bills"), and, perhaps, sauropodomorphs (mostly large herbivorous quadrupeds with long necks and tails) (Dell BAT30WL battery).

The common House Sparrow (Passer domesticus) is often used to represent modern birds in definitions of the group Dinosauria

Many paleontologists note that the point at which sauropodomorphs and theropods diverged may omit sauropodomorphs from the definition for both saurischians and dinosaurs. To avoid instability, Dinosauria can be more conservatively defined with respect to four anchoring nodes: Triceratops horridus, Saltasaurus loricatus(Dell D6400 battery), and Passer domesticus, their most recent common ancestor, and all descendants. This "safer" definition can be expressed as "Dinosauria = Ornithischia + Sauropodomorpha + Theropoda".[12]

There is near universal consensus among paleontologists that birds are the descendants of theropod dinosaurs. In traditional taxonomy, birds were considered a separate "class" which had evolved from dinosaurs(Dell HF674 battery). However, a majority of modern paleontologists reject the traditional style of classification in favor of phylogenetic nomenclature, which requires that all descendants of a single common ancestor must be included in a group for that group to be natural. Birds are thus considered by most modern scientists to be dinosaurs and dinosaurs are, therefore, not extinct(Dell N3010 battery). Birds are classified by most paleontologists as belonging to the subgroup Maniraptora, which are coelurosaurs, which are theropods, which are saurischians, which are dinosaurs.[13]

General description

Using one of the above definitions, dinosaurs can be generally described as archosaurs with limbs held erect beneath the body.[14] Many prehistoric animal groups are popularly conceived of as dinosaurs, such as ichthyosaurs, mosasaurs, plesiosaurs(Dell Inspiron N4010 battery), pterosaurs, and Dimetrodon, but are not classified scientifically as dinosaurs, and none had the erect limb posture characteristic of true dinosaurs.[15] Dinosaurs were the dominant terrestrial vertebrates of the Mesozoic, especially the Jurassic and Cretaceous periods. Other groups of animals were restricted in size and niches; mammals, for example(Dell INSPIRON 1100 battery), rarely exceeded the size of a cat, and were generally rodent-sized carnivores of small prey.[16] One notable exception is Repenomamus giganticus, a triconodont weighing between 12 kilograms (26 lb) and 14 kilograms (31 lb) that is known to have eaten small dinosaurs like young Psittacosaurus. (Dell Inspiron 1200 battery)

Stegosaurus stenops skeleton, Field Museum

Dinosaurs have always been an extremely varied group of animals; according to a 2006 study, over 500 non-avialan dinosaur genera have been identified with certainty so far, and the total number of genera preserved in the fossil record has been estimated at around 1850, nearly 75% of which remain to be discovered. (Dell Inspiron 1420 battery) An earlier study predicted that about 3400 dinosaur genera existed, including many which would not have been preserved in the fossil record.[18] By September 17, 2008, 1047 different species of dinosaurs had been named.[5] Some are herbivorous, others carnivorous. While most dinosaurs have been bipeds, some prehistoric species were quadrupeds, and others, such as Ammosaurus and Iguanodon(Dell Inspiron 1464 battery), could walk just as easily on two or four legs. Cranial modifications like horns and crests are common among dinosaurs, and some extinct species had bony armor. Although known for large size, many Mesozoic dinosaurs were human-sized or smaller, and modern birds are generally very small in size. Dinosaurs today inhabit every continents, (Dell Inspiron 1564 battery) and fossils show that they had achieved global distribution by at least the early Jurassic period.[6] Modern birds inhabit most available habitats, from terrestrial to marine, and there is evidence that some non-avialan dinosaurs (such as Microraptor) could fly or at least glide, and others, such as spinosaurids, had semi-aquatic habits.[19]

Distinguishing anatomical features(Dell Inspiron 1764 battery)

While recent discoveries have made it more difficult to present a universally agreed-upon list of dinosaurs' distinguishing features, nearly all dinosaurs discovered so far share certain modifications to the ancestral archosaurian skeleton. Although some later groups of dinosaurs featured further modified versions of these traits(Dell Inspiron 1520 battery), they are considered typical across Dinosauria; the earliest dinosaurs had them and passed them on to all their descendants. Such common features across a taxonomic group are called synapomorphies.

A detailed assessment of archosaur interrelations by S. Nesbitt[20] confirmed or found the following 12 unambiguous synapomorphies, some previously known:

in the skull, a supratemporal fossa (excavation) is present in front of the supratemporal fenestra

epipophyses present in anterior neck vertebrae (except atlas and axis) (Dell Inspiron 1521 battery)

apex of deltopectoral crest (a projection on which the deltopectoral muscles attach) located at or more than 30% down the length of the humerus (upper arm bone)

radius shorter than 80% of humerus length

fourth trochanter (projection where the caudofemoralis muscle attaches) on the femur (thigh bone) is a sharp flange

fourth trochanter asymmetrical, with distal margin forming a steeper angle to the shaft(Dell inspiron 1525 battery)

on the astragalus and calcaneum the proximal articular facet for fibula occupies less than 30% of the transverse width of the element

exocciptials (bones at the back of the skull) do not meet along the midline on the floor of the endocranial cavity

proximal articular surfaces of the ischium with the ilium and the pubis separated by a large concave surface

cnemial crest on the tibia (shinbone) arcs anterolaterally(Dell inspiron 1526 battery)

distinct proximodistally oriented ridge present on the posterior face of the distal end of the tibia

Nesbitt found a number of further potential synapomorphies, and discounted a number of synapomorphies previously suggested. Some of these are also present in silesaurids, which Nesbitt recovered as a sister group to Dinosauria, including a large anterior trochanter(Dell Inspiron 1720 battery), metatarsals II and IV of subequal length, reduced contact between ischium and pubis, the presence of a cenmial crest on the tibia and of an ascending process on the astragalus,[10] and many others.

Diagram of a typical diapsid skull

Hip joints and hindlimb postures of typical reptiles (left), dinosaurs and mammals (middle), and rauisuchians (right)

A variety of other skeletal features are shared by dinosaurs. However, because they are either common to other groups of archosaurs or were not present in all early dinosaurs, these features are not considered to be synapomorphies(Dell Inspiron 2000 battery). For example, as diapsids, dinosaurs ancestrally had two pairs of temporal fenestrae (openings in the skull behind the eyes), and as members of the diapsid group Archosauria, had additional openings in the snout and lower jaw.[21] Additionally, several characteristics once thought to be synapomorphies are now known to have appeared before dinosaurs, or were absent in the earliest dinosaurs and independently evolved by different dinosaur groups(Dell INSPIRON 2600 battery). These include an elongated scapula, or shoulder blade; a sacrum composed of three or more fused vertebrae (three are found in some other archosaurs, but only two are found in Herrerasaurus);[10] and an acetabulum, or hip socket, with a hole at the center of its inside surface (closed in Saturnalia, for example). (Dell INSPIRON 3800 battery) Another difficulty of determining distinctly dinosaurian features is that early dinosaurs and other archosaurs from the Late Triassic are often poorly known and were similar in many ways; these animals have sometimes been misidentified in the literature.[23]

Dinosaurs stand erect in a manner similar to most modern mammals, but distinct from most other reptiles, whose limbs sprawl out to either side.[24] This posture is due to the development of a laterally facing recess in the pelvis (usually an open socket) (Dell INSPIRON 4000 battery) and a corresponding inwardly facing distinct head on the femur.[25] Their erect posture enabled early dinosaurs to breathe easily while moving, which likely permitted stamina and activity levels that surpassed those of "sprawling" reptiles.[26] Erect limbs probably also helped support the evolution of large size by reducing bending stresses on limbs. (Dell Inspiron 5000 battery) Some non-dinosaurian archosaurs, including rauisuchians, also had erect limbs but achieved this by a "pillar erect" configuration of the hip joint, where instead of having a projection from the femur insert on a socket on the hip, the upper pelvic bone was rotated to form an overhanging shelf. (Dell INSPIRON 500M battery)

Evolutionary history

Main article: Evolution of dinosaurs

Origins and early evolution

Skeleton of Marasuchus lilloensis, a dinosaur-like ornithodiran

The early forms Herrerasaurus (large), Eoraptor (small) and a Plateosaurus skull

Dinosaurs diverged from their archosaur ancestors approximately 230 million years ago during the Middle to Late Triassic period, roughly 20 million years after the Permian–Triassic extinction event wiped out an estimated 95% of all life on Earth. (Dell INSPIRON 5100 battery) Radiometric dating of the rock formation that contained fossils from the early dinosaur genus Eoraptor establishes its presence in the fossil record at this time. Paleontologists think that Eoraptor resembles the common ancestor of all dinosaurs;[30] if this is true, its traits suggest that the first dinosaurs were small, bipedal predators.[31] The discovery of primitive(Dell INSPIRON 510M battery), dinosaur-like ornithodirans such as Marasuchus and Lagerpeton in Argentinian Middle Triassic strata supports this view; analysis of recovered fossils suggests that these animals were indeed small, bipedal predators.

When dinosaurs appeared, terrestrial habitats were occupied by various types of archosaurs and therapsids, such as aetosaurs, cynodonts, dicynodonts, ornithosuchids, rauisuchians, and rhynchosaurs(Dell INSPIRON 6000 battery). Most of these other animals became extinct in the Triassic, in one of two events. First, at about the boundary between the Carnian and Norian faunal stages (about 215 million years ago), dicynodonts and a variety of basal archosauromorphs, including the prolacertiforms and rhynchosaurs, became extinct. This was followed by the Triassic–Jurassic extinction event (about 200 million years ago) (Dell INSPIRON 600M battery), that saw the end of most of the other groups of early archosaurs, like aetosaurs, ornithosuchids, phytosaurs, and rauisuchians. These losses left behind a land fauna of crocodylomorphs, dinosaurs, mammals, pterosaurians, and turtles.[10] The first few lines of early dinosaurs diversified through the Carnian and Norian stages of the Triassic, most likely by occupying the niches of the groups that became extinct(Dell Inspiron 6400 battery).

Evolution and paleobiogeography

Dinosaur evolution after the Triassic follows changes in vegetation and the location of continents. In the Late Triassic and Early Jurassic, the continents were connected as the single landmass Pangaea, and there was a worldwide dinosaur fauna mostly composed of coelophysoid carnivores and early sauropodomorph herbivores.[32] Gymnosperm plants (particularly conifers) (Dell INSPIRON 7000 battery), a potential food source, radiated in the Late Triassic. Early sauropodomorphs did not have sophisticated mechanisms for processing food in the mouth, and so must have employed other means of breaking down food farther along the digestive tract.[33] The general homogeneity of dinosaurian faunas continued into the Middle and Late Jurassic, where most localities had predators consisting of ceratosaurians(Dell INSPIRON 700M battery), spinosauroids, and carnosaurians, and herbivores consisting of stegosaurian ornithischians and large sauropods. Examples of this include the Morrison Formation of North America and Tendaguru Beds of Tanzania. Dinosaurs in China show some differences, with specialized sinraptorid theropods and unusual, long-necked sauropods like Mamenchisaurus.[32] Ankylosaurians and ornithopods were also becoming more common(Dell Inspiron 710m battery), but prosauropods had become extinct. Conifers and pteridophytes were the most common plants. Sauropods, like the earlier prosauropods, were not oral processors, but ornithischians were evolving various means of dealing with food in the mouth, including potential cheek-like organs to keep food in the mouth, and jaw motions to grind food(Dell INSPIRON 8200 battery).[33] Another notable evolutionary event of the Jurassic was the appearance of true birds, descended from maniraptoran coelurosaurians.[13]

Earth during the Jurassic, the period in which dinosaurs gained global distribution. The continents were in different locations from where they are today.

By the Early Cretaceous and the ongoing breakup of Pangaea, dinosaurs were becoming strongly differentiated by landmass. The earliest part of this time saw the spread of ankylosaurians, iguanodontians, and brachiosaurids through Europe, North America(Dell INSPIRON 8600 battery), and northern Africa. These were later supplemented or replaced in Africa by large spinosaurid and carcharodontosaurid theropods, and rebbachisaurid and titanosaurian sauropods, also found in South America. In Asia, maniraptoran coelurosaurians like dromaeosaurids, troodontids, and oviraptorosaurians became the common theropods(Dell INSPIRON 9100 battery), and ankylosaurids and early ceratopsians like Psittacosaurus became important herbivores. Meanwhile, Australia was home to a fauna of basal ankylosaurians, hypsilophodonts, and iguanodontians.[32] The stegosaurians appear to have gone extinct at some point in the late Early Cretaceous or early Late Cretaceous. A major change in the Early Cretaceous, which would be amplified in the Late Cretaceous(Dell INSPIRON 9200 battery), was the evolution of flowering plants. At the same time, several groups of dinosaurian herbivores evolved more sophisticated ways to orally process food. Ceratopsians developed a method of slicing with teeth stacked on each other in batteries, and iguanodontians refined a method of grinding with tooth batteries, taken to its extreme in hadrosaurids. (Dell INSPIRON 9300 battery) Some sauropods also evolved tooth batteries, best exemplified by the rebbachisaurid Nigersaurus.[34]

There were three general dinosaur faunas in the Late Cretaceous. In the northern continents of North America and Asia, the major theropods were tyrannosaurids and various types of smaller maniraptoran theropods, with a predominantly ornithischian herbivore assemblage of hadrosaurids, ceratopsians, ankylosaurids(Dell Inspiron 9400 battery), and pachycephalosaurians. In the southern continents that had made up the now-splitting Gondwana, abelisaurids were the common theropods, and titanosaurian sauropods the common herbivores. Finally, in Europe, dromaeosaurids, rhabdodontid iguanodontians, nodosaurid ankylosaurians, and titanosaurian sauropods were prevalent.[32] Flowering plants were greatly radiating, (Dell Inspiron E1505 battery) with the first grasses appearing by the end of the Cretaceous.[35] Grinding hadrosaurids and shearing ceratopsians became extremely diverse across North America and Asia. Theropods were also radiating as herbivores or omnivores, with therizinosaurians and ornithomimosaurians becoming common. (Dell Inspiron E1705 battery)

The Cretaceous–Paleogene extinction event, which occurred approximately 65 million years ago at the end of the Cretaceous period, caused the extinction of all dinosaur groups except for the neornithine birds. Some other diapsid groups, such as crocodilians, sebecosuchians, turtles, lizards, snakes, sphenodontians, and choristoderans, also survived the event. (Dell Inspiron Mini 9 battery)

The surviving lineages of neornithine birds, including the ancestors of modern ratites, ducks and chickens, and a variety of waterbirds, diversified rapidly at the beginning of the Paleogene period, entering ecological niches left vacant by the extinction of Mesozoic dinosaur groups such as the arboreal enantiornithines, aquatic hesperornithines(Dell Latitude D400 battery), and even the larger terrestrial theropods (in the form of Gastornis, mihirungs, and "terror birds"). However, mammals were also rapidly diversifying during this time, and out-competed the neornithines for dominance of most terrestrial niches.[37]

Classification

Main article: Dinosaur classification

Dinosaurs are archosaurs, like modern crocodilians. Within the archosaur group, dinosaurs are differentiated most noticeably by their gait. Dinosaur legs extend directly beneath the body, whereas the legs of lizards and crocodilians sprawl out to either side(Dell STUDIO 1450 battery).

Collectively, dinosaurs as a clade are divided into two primary branches, Saurischia and Ornithischia. Saurischia includes those taxa sharing a more recent common ancestor with birds than with Ornithischia, while Ornithischia includes all taxa sharing a more recent common ancestor with Triceratops than with Saurischia(Dell Vostro 1400 battery). Anatomically, these two groups can be distinguished most noticeably by their pelvic structure. Early saurischians—"lizard-hipped", from the Greek sauros (σαῦρος) meaning "lizard" and ischion (ἰσχίον) meaning "hip joint—retained the hip structure of their ancestors, with a pubis bone directed cranially, or forward. (Dell Vostro 1500 battery) This basic form was modified by rotating the pubis backward to varying degrees in several groups (Herrerasaurus,[38] therizinosauroids,[39] dromaeosaurids,[40] and birds[13]). Saurischia includes the theropods (exclusively bipedal and with a wide variety of diets) and sauropodomorphs (long-necked herbivores which include advanced, quadrupedal groups) (Dell XPS GEN 2 battery).

By contrast, ornithischians—"bird-hipped", from the Greek ornitheios (ὀρνίθειος) meaning "of a bird" and ischion (ἰσχίον) meaning "hip joint"—had a pelvis that superficially resembled a bird's pelvis: the pubis bone was oriented caudally (rear-pointing). Unlike birds, the ornithischian pubis also usually had an additional forward-pointing process(Dell XPS M1210 battery). Ornithischia includes a variety of species which were primarily herbivores. (NB: the terms "lizard hip" and "bird hip" are misnomers – birds evolved from dinosaurs with "lizard hips".)

Taxonomy

The following is a simplified classification of dinosaur groups based on their evolutionary relationships, and organized based on the list of Mesozoic dinosaur species provided by Holtz (2008).[41] A more detailed version can be found at Dinosaur classification. The cross (†) is used to signify groups with no living members(Dell XPS M1330 battery).

Dinosauria

Saurischia ("lizard-hipped"; includes Theropoda and Sauropodomorpha)

Theropoda (all bipedal; most were carnivorous)

†Herrerasauria (early bipedal carnivores)

†Coelophysoidea (small, early theropods; includes Coelophysis and close relatives)

†Dilophosauridae (early crested and carnivorous theropods)

†Ceratosauria (generally elaborately horned, the dominant southern carnivores of the Cretaceous) (Dell XPS 1340 battery)

Tetanurae ("stiff tails"; includes most theropods)

†Megalosauroidea (early group of large carnivores including the semi-aquatic spinosaurids)

†Carnosauria (Allosaurus and close relatives, like Carcharodontosaurus)

Coelurosauria (feathered theropods, with a range of body sizes and niches)

†Compsognathidae (common early coelurosaurs with reduced forelimbs)

†Tyrannosauridae (Tyrannosaurus and close relatives; had reduced forelimbs) (Dell XPS M1530 battery)

†Ornithomimosauria ("ostrich-mimics"; mostly toothless; carnivores to possible herbivores)

†Alvarezsauroidea (small insectivores with reduced forelimbs each bearing one enlarged claw)

Maniraptora ("hand snatchers"; had long, slender arms and fingers)

†Therizinosauria (bipedal herbivores with large hand claws and small heads)

†Oviraptorosauria (mostly toothless; their diet and lifestyle are uncertain)

†Archaeopterygidae (small, winged theropods or primitive birds) (Dell XPS M170 battery)

†Deinonychosauria (small- to medium-sized; bird-like, with a distinctive toe claw)

Avialae (modern birds and extinct relatives)

†Scansoriopterygidae (small primitive avialans with long third fingers)

†Omnivoropterygidae (large, early short-tailed avialans)

†Confuciusornithidae (small toothless avialans)

†Enantiornithes (primitive tree-dwelling, flying avialans)

Euornithes (advanced flying birds)

†Yanornithiformes (toothed Cretaceous Chinese birds)

†Hesperornithes (specialized aquatic diving birds) (Dell XPS M1710 battery)

Aves (modern, beaked birds and their extinct relatives)

Several macronarian Sauropods: from left to right Camarasaurus, Brachiosaurus, Giraffatitan, and Euhelopus

†Sauropodomorpha (herbivores with small heads, long necks, long tails)

†Guaibasauridae (small, primitive, omnivorous sauropodomorphs)

†Plateosauridae (primitive, strictly bipedal "prosauropods")

†Riojasauridae (small, primitive sauropodomorphs)

†Massospondylidae (small, primitive sauropodomorphs) (Dell XPS M1730 battery)

†Sauropoda (very large and heavy, usually over 15 meters (49 feet) long; quadrupedal)

†Vulcanodontidae (primitive sauropods with pillar-like limbs)

†Eusauropoda ("true sauropods")

†Cetiosauridae ("whale reptiles")

†Turiasauria (European group of Jurassic and Cretaceous sauropods)

†Neosauropoda ("new sauropods")

†Diplodocoidea (skulls and tails elongated; teeth typically narrow and pencil-like)

†Macronaria (boxy skulls; spoon- or pencil-shaped teeth)

†Brachiosauridae (long-necked, long-armed macronarians) (Dell XPS M2010 battery)

†Titanosauria (diverse; stocky, with wide hips; most common in the Late Cretaceous of southern continents)

Various ornithopod dinosaurs and one heterodontosaurid. Far left: Camptosaurus, left: Iguanodon, center background: Shantungosaurus, center foreground: Dryosaurus, right: Corythosaurus, far right (small): Heterodontosaurus, far right (large) Tenontosaurus.

†Ornithischia ("bird-hipped"; diverse bipedal and quadrupedal herbivores) (Dell Latitude E5400 battery)

†Heterodontosauridae (small basal ornithopod herbivores/omnivores with prominent canine-like teeth)

†Thyreophora (armored dinosaurs; mostly quadrupeds)

†Ankylosauria (scutes as primary armor; some had club-like tails)

†Stegosauria (spikes and plates as primary armor)

†Neornithischia ("new ornithischians")

†Ornithopoda (various sizes; bipeds and quadrupeds; evolved a method of chewing using skull flexibility and numerous teeth) (Dell Latitude E5500 battery)

†Marginocephalia (characterized by a cranial growth)

†Pachycephalosauria (bipeds with domed or knobby growth on skulls)

†Ceratopsia (quadrupeds with frills; many also had horns)

Biology

Knowledge about dinosaurs is derived from a variety of fossil and non-fossil records, including fossilized bones, feces, trackways, gastroliths, feathers, impressions of skin, internal organs and soft tissues.[42][43] Many fields of study contribute to our understanding of dinosaurs, including physics (especially biomechanics) (Dell Latitude E6400 battery), chemistry, biology, and the earth sciences (of which paleontology is a sub-discipline). Two topics of particular interest and study have been dinosaur size and behavior.

Size

Main article: Dinosaur size

Scale diagram comparing the largest known dinosaurs in five major clades and a human

Current evidence suggests that dinosaur average size varied through the Triassic, early Jurassic, late Jurassic and Cretaceous periods.[30] Theropod dinosaurs, when sorted by estimated weight into categories based on order of magnitude(Dell Latitude E6500 battery), most often fall into the 100 to 1000 kilogram (220 to 2200 lb) category, whereas recent predatory carnivorans peak in the 10 to 100 kilogram (22 to 220 lb) category.[44] The mode of dinosaur body masses is between one and ten metric tonnes.[45] This contrasts sharply with the size of Cenozoic mammals, estimated by the National Museum of Natural History as about 2 to 5 kilograms (5 to 10 lb). (Dell Inspiron Mini 12 battery)

The sauropods were the largest and heaviest dinosaurs. For much of the dinosaur era, the smallest sauropods were larger than anything else in their habitat, and the largest were an order of magnitude more massive than anything else that has since walked the Earth. Giant prehistoric mammals such as the Paraceratherium (the largest land mammal ever) (Dell XPS M140 battery) were dwarfed by the giant sauropods, and only modern whales approach or surpass them in size.[47] There are several proposed advantages for the large size of sauropods, including protection from predation, reduction of energy use, and longevity, but it may be that the most important advantage was dietary(Dell XPS 13 battery). Large animals are more efficient at digestion than small animals, because food spends more time in their digestive systems. This also permits them to subsist on food with lower nutritive value than smaller animals. Sauropod remains are mostly found in rock formations interpreted as dry or seasonally dry, and the ability to eat large quantities of low-nutrient browse would have been advantageous in such environments. (Dell XPS 16 battery)

Largest and smallest

Scientists will probably never be certain of the largest and smallest dinosaurs. This is because only a tiny percentage of animals ever fossilize, and most of these remain buried in the earth. Few of the specimens that are recovered are complete skeletons, and impressions of skin and other soft tissues are rare. Rebuilding a complete skeleton by comparing the size and morphology of bones to those of similar(Dell XPS 1640 battery), better-known species is an inexact art, and reconstructing the muscles and other organs of the living animal is, at best, a process of educated guesswork.

Comparative size of Giraffatitan

The tallest and heaviest dinosaur known from good skeletons is Giraffatitan brancai (previously classified as a species of Brachiosaurus). Its remains were discovered in Tanzania between 1907–12. Bones from several similar-sized individuals were incorporated into the skeleton now mounted and on display at the Museum für Naturkunde Berlin(Dell XPS 1645 battery);[49] this mount is 12 meters (39 ft) tall and 22.5 meters (74 ft) long, and would have belonged to an animal that weighed between 30000 and 60000 kilograms (70000 and 130000 lb). The longest complete dinosaur is the 27-meter (89 ft) long Diplodocus, which was discovered in Wyoming in the United States and displayed in Pittsburgh's Carnegie Natural History Museum in 1907(Dell XPS 1647 battery).

Comparative size of Eoraptor

There were larger dinosaurs, but knowledge of them is based entirely on a small number of fragmentary fossils. Most of the largest herbivorous specimens on record were all discovered in the 1970s or later, and include the massive Argentinosaurus, which may have weighed 80000 to 100000 kilograms (90 to 110 short tons); some of the longest were the 33.5 meters (Dell Latitude 131L battery) (110 ft) long Diplodocus hallorum[48] (formerly Seismosaurus) and the 33 meters (108 ft) long Supersaurus;[50] and the tallest, the 18 meters (59 ft) tall Sauroposeidon, which could have reached a sixth-floor window. The heaviest and longest of them all may have been Amphicoelias fragillimus, known only from a now lost partial vertebral neural arch described in 1878(Dell Latitude C400 battery). Extrapolating from the illustration of this bone, the animal may have been 58 meters (190 ft) long and weighed over 120000 kg (260000 lb).[48] The largest known carnivorous dinosaur was Spinosaurus, reaching a length of 16 to 18 meters (52 to 60 ft), and weighing in at 8150 kg (18000 lb).[51] Other large meat-eaters included Giganotosaurus, Carcharodontosaurus and Tyrannosaurus. (Dell Latitude C500 battery)

Not including birds (Avialae), the smallest known dinosaurs were about the size of a pigeon.[53] Not surprisingly, the smallest dinosaurs were theropods closely related to birds. Anchiornis, for example, had a total skeletal length of under 35 centimeters (1.1 ft).[53][54] Anchiornis is currently the smallest dinosaur described from an adult specimen(Dell Latitude C510 battery), with an estimated weight of 110 grams.[54] The smallest herbivorous non-avialan dinosaurs included Microceratus and Wannanosaurus, at about 60 cm (2 ft) long each.

Behavior

A nesting ground of hadrosaur Maiasaura peeblesorum was discovered in 1978.

Many modern birds are highly social, often found living in flocks. There is general agreement that some behaviors which are common in birds, as well as in crocodiles (bird' closest living relatives), were also common among extinct dinosaur groups(Dell Latitude C540 battery). Interpretations of behavior in fossil species are generally based on the pose of skeletons and their habitat, computer simulations of their biomechanics, and comparisons with modern animals in similar ecological niches.

The first potential evidence for herding or flocking as a widespread behavior common to many dinosaur groups in addition to birds was the 1878 discovery of 31 Iguanodon bernissartensis(Dell Latitude C600 battery), ornithischians which were then thought to have perished together in Bernissart, Belgium, after they fell into a deep, flooded sinkhole and drowned.[56] Other mass-death sites have been subsequently discovered. Those, along with multiple trackways, suggest that gregarious behavior was common in many early dinosaur species. Trackways of hundreds or even thousands of herbivores indicate that duck-bills (hadrosaurids) (Dell Latitude C610 battery) may have moved in great herds, like the American Bison or the African Springbok. Sauropod tracks document that these animals traveled in groups composed of several different species, at least in Oxfordshire, England,[57] although there is not evidence for specific herd structures.[58] Congregated into herds may have evolved for defense, for migratory purposes, or to provide protection for young(Dell Latitude C640 battery). There is evidence that many types of slow-growing dinosaurs, including various theropods, sauropods, ankylosaurians, ornithopods, and ceratopsians, formed aggregations of immature individuals. One example is a site in Inner Mongolia that has yielded the remains of over 20 Sinornithomimus, from one to seven years old. This assemblage is interpreted as a social group that was trapped in mud. (Dell Latitude C800 battery) The interpretation of dinosaurs as gregarious has also extended to depicting carnivorous theropods as pack hunters working together to bring down large prey.[60][61] However, this lifestyle is uncommon among modern birds, crocodiles, and other reptiles, and the taphonomic evidence suggesting mammal-like pack hunting in such theropods as Deinonychus and Allosaurus can also be interpreted as the results of fatal disputes between feeding animals, as is seen in many modern diapsid predators. (Dell Latitude C810 battery)

Artist's rendering of two Centrosaurus apertus engaged in intra-specific combat.

The crests and frills of some dinosaurs, like the marginocephalians, theropods and lambeosaurines, may have been too fragile to be used for active defense, and so they were likely used for sexual or aggressive displays, though little is known about dinosaur mating and territorialism. Head wounds from bites suggest that theropods(Dell Latitude C840 battery), at least, engaged in active aggressive confrontations.[63]

From a behavioral standpoint, one of the most valuable dinosaur fossils was discovered in the Gobi Desert in 1971. It included a Velociraptor attacking a Protoceratops,[64] providing evidence that dinosaurs did indeed attack each other.[65] Additional evidence for attacking live prey is the partially healed tail of an Edmontosaurus, a hadrosaurid dinosaur(Dell Latitude CPI battery); the tail is damaged in such a way that shows the animal was bitten by a tyrannosaur but survived.[65] Cannibalism amongst some species of dinosaurs was confirmed by tooth marks found in Madagascar in 2003, involving the theropod Majungasaurus.[66]

Comparisons between the scleral rings of dinosaurs and modern birds and reptiles have been used to infer daily activity patterns of dinosaurs(Dell Latitude CPX battery). Although it has been suggested that most dinosaurs were active during the day, these comparisons have shown that small predatory dinosaurs such as dromaeosaurids, Juravenator, and Megapnosaurus were likely nocturnal. Large and medium-sized herbivorous and omnivorous dinosaurs such as ceratopsians, sauropodomorphs, hadrosaurids, ornithomimosaurs may have been cathemeral(Dell Latitude D410 battery), active during short intervals throughout the day, although the small ornithischian Agilisaurus was inferred to be diurnal.[67]

Based on current fossil evidence from dinosaurs such as Oryctodromeus, some ornithischian species seem to have led a partially fossorial (burrowing) lifestyle.[68] Many modern birds are arboreal (tree climbing), and this was also true of many Mesozoic birds(Dell Latitude D420 battery), especially the enantiornithines.[69] While some early bird-like species may have already been arboreal as well (including dromaeosaurids such as Microraptor[70]) most non-avialan dinosaurs seem to have relied on land-based locomotion. A good understanding of how dinosaurs moved on the ground is key to models of dinosaur behavior; the science of biomechanics(Dell Latitude D430 battery), in particular, has provided significant insight in this area. For example, studies of the forces exerted by muscles and gravity on dinosaurs' skeletal structure have investigated how fast dinosaurs could run,[71] whether diplodocids could create sonic booms via whip-like tail snapping,[72] and whether sauropods could float. (Dell Latitude D500 battery)

Communication

Artists impression of a striking and unusual visual display in a Lambeosaurus magnicristatus

Modern birds are well known for communicating using primarily visual and auditory signals, and the wide diversity of visual display structures among fossil dinosaur groups suggests that visual communication has always been important to dinosaur biology(Dell Latitude D505 battery). However, the evolution of dinosaur vocalization is less certain. In 2008, paleontologist Phil Senter examined the evidence for vocalization in Mesozoic animal life, including dinosaurs.[74] Senter found that, contrary to popular depictions of roaring dinosaurs in motion pictures, it is likely that most Mesozoic dinosaurs were not capable of creating any vocalizations (Dell Latitude D510 battery) (though the hollow crests of the lambeosaurines could have functioned as resonance chambers used for a wide range of vocalizations).[75][76] To draw this conclusion, Senter studied the distribution of vocal organs in modern reptiles and birds. He found that vocal cords in the larynx probably evolved multiple times among reptiles, including crocodilians, which are able to produce guttural roars(Dell Latitude D520 battery). Birds, on the other hand, lack a larynx. Instead, bird calls are produced by the syrinx, a vocal organ found only in birds, and which is not related to the larynx, meaning it evolved independently from the vocal organs in reptiles. The syrinx depends on the air sac system in birds to function; specifically, it requires the presence of a clavicular air sac near the wishbone or collar bone(Dell Latitude D600 battery). This air sac leaves distinctive marks or opening on the bones, including a distinct opening in the upper arm bone (humerus). While extensive air sac systems are a unique characteristic of saurischian dinosaurs, the clavicular air sac necessary to vocalize does not appear in the fossil record until the enantiornithines (one exception, Aerosteon, probably evolved its clavicular air sac independently of birds for reasons other than vocalization). (Dell Latitude D610 battery)

The most primitive dinosaurs with evidence of a vocalizing syrinx are the enantironithine birds. Any bird-line archosaurs more primitive than this probably did not make vocal calls. Rather, several lines of evidence suggest that early dinosaurs used primarily visual communication, in the form of distinctive-looking (and possibly brightly colored) horns, frills, crests(Dell Latitude D620 battery), sails and feathers. This is similar to some modern reptile groups such as lizards, in which many forms are largely silent (though like dinosaurs they possess well-developed senses of hearing) but use complex coloration and display behaviors to communicate.[74]

In addition, dinosaurs use other methods of producing sound for communication. Other animals, including other reptiles(Dell Latitude D630 battery), use a wide variety of non-vocal sound communication, including hissing, jaw grinding or clapping, use of environment (such as splashing), and wing beating (possible in winged maniraptoran dinosaurs).[74]

Reproductive biology

Nest of a plover (Charadrius).

All dinosaurs lay amniotic eggs with hard shells made mostly of calcium carbonate.[citation needed] Eggs are usually laid in a nest. Most species create somewhat elaborate nests, which can be cups, domes, plates, beds scrapes, mounds, or burrows. (Dell Latitude D800 battery) Some species of modern bird have no nests; the cliff-nesting Common Guillemot lays its eggs on bare rock, and male Emperor Penguins keep eggs between their body and feet. Primitive birds and many non-avialan dinosaurs often lay eggs in communal nests, with males primarily incubating the eggs(Dell Latitude D810 battery). While modern birds have only one functional oviduct and lay one egg at a time, more primitive birds and dinosaurs had two oviducts, like crocodiles. Some non-avialan dinosaurs, such as Troodon, exhibited iterative laying, where the adult might lay a pair of eggs every one or two days, and then ensured simultaneous hatching by delaying brooding until all eggs were laid. (Dell Latitude D820 battery)

When laying eggs, females grow a special type of bone between the hard outer bone and the marrow of their limbs. This medullary bone, which is rich in calcium, is used to make eggshells. A discovery of features in a Tyrannosaurus rex skeleton provided evidence of medullary bone in extinct dinosaurs and, for the first time, allowed paleontologists to establish the sex of a fossil dinosaur specimen(Dell Latitude D830 battery). Further research has found medullary bone in the theropod Allosaurus and the ornithopod Tenontosaurus. Because the line of dinosaurs that includes Allosaurus and Tyrannosaurus diverged from the line that led to Tenontosaurus very early in the evolution of dinosaurs, this suggests that dinosaurs in general produced medullary tissue. (Dell Latitude 2100 battery)

Fossilized egg of the oviraptorid Citipati, American Museum of Natural History

Another widespread trait among modern birds is parental care for young after hatching. Jack Horner's 1978 discovery of a Maiasaura ("good mother lizard") nesting ground in Montana demonstrated that parental care continued long after birth among ornithopods, suggesting this behavior might have been common to all dinosaurs. (Dell Latitude 2110 battery) There is also evidence that other non-theropod dinosaurs, like Patagonian titanosaurian sauropods (1997 discovery), also nested in large groups.[81] A specimen of the Mongolian oviraptorid Citipati osmolskae was discovered in a chicken-like brooding position in 1993, which indicates that they had begun using an insulating layer of feathers to keep the eggs warm. (Dell Latitude E4300 battery) Parental care being a trait common to all dinosaurs is supported by other finds. For example, the fossilized remains of a grouping of Psittacosaurus has been found, consisting of one adult and 34 juveniles; in this case, the large number of juveniles may be due to communal nesting.[83] Additionally, a dinosaur embryo (pertaining to the prosauropod Massospondylus) was found without teeth(Dell Vostro 1310 battery), indicating that some parental care was required to feed the young dinosaurs.[84] Trackways have also confirmed parental behavior among ornithopods from the Isle of Skye in northwestern Scotland.[85] Nests and eggs have been found for most major groups of dinosaurs, and it appears likely that all dinosaurs cared for their young to some extent either before or shortly after hatching(Dell Vostro 1320 battery).

Waste

Like other reptiles, dinosaurs are primarily uricotelic, that is, their kidneys extract nitrogenous wastes from their bloodstream and excrete it as uric acid instead of urea or ammonia via the ureters into the intestine. In most living species, uric acid is excreted along with feces as a semisolid waste.[86][87][88] However, at least some modern birds (Dell Vostro 1510 battery) (such as hummingbirds) can be facultatively ammonotelic, excreting most of the nitrogenous wastes as ammonia.[89] They also excrete creatine, rather than creatinine like mammals. This material, as well as the output of the intestines, emerges from the cloaca.[90][91] In addition, many species regurgitate pellets, and fossil pellets that may have come from dinosaurs are known from as long ago as the Cretaceous period. (Dell Vostro 1520 battery)

Physiology

Main article: Physiology of dinosaurs

Comparison between the air sacs of an abelisaur and a bird

Because both modern crocodilians and birds have four-chambered hearts (albeit modified in crocodilians), it is likely that this is a trait shared by all archosaurs, including all dinosaurs.[93] While all modern birds have high metabolisms and are "warm blooded" (endothermic), a vigorous debate has been ongoing since the 1960s regarding how far back in the dinosaur lineage this trait extends(Dell Vostro 2510 battery). Originally, scientists broadly disagreed as to whether non-avian dinosaurs or even early birds were capable of regulating their body temperatures at all. More recently, endothermy for all dinosaurs has become the consensus view, and debate has focused on the mechanisms of temperature regulation(Dell Vostro 1014 battery).

After non-avian dinosaurs were discovered, paleontologists first posited that they were ectothermic. This supposed "cold-bloodedness" was used to imply that the ancient dinosaurs were relatively slow, sluggish organisms, even though many modern reptiles are fast and light-footed despite relying on external sources of heat to regulate their body temperature(Dell Inspiron 1410 battery). The idea of dinosaurs as ectothermic and sluggish remained a prevalent view until Robert T. "Bob" Bakker, an early proponent of dinosaur endothermy, published an influential paper on the topic in 1968.[94]

Modern evidence indicates that even non-avian dinosaurs and birds thrived in cooler temperate climates, and that at least some early species must have regulated their body temperature by internal biological means (Dell Vostro 1014N battery) (aided by the animals' bulk in large species and feathers or other body coverings in smaller species). Evidence of endothermy in Mesozoic dinosaurs includes the discovery of polar dinosaurs in Australia and Antarctica (where they would have experienced a cold, dark six-month winter), and analysis of blood-vessel structures within fossil bones that are typical of endotherms(Dell Vostro 1015 battery). Scientific debate continues regarding the specific ways in which dinosaur temperature regulation evolved.[95]

In the saurischian dinosaurs, higher metabolisms may have been supported by the evolution of a bird-like repiratory system characterized by an extensive system of air sacs that extended the lungs and invaded many of the bones in the skeleton, making them hollow. (Dell Inspiron 1088 battery)

Early dinosaurian respiratory systems with air sacs may have been capable of sustaining higher activity levels than mammals of similar size and build can sustain. In addition to providing a very efficient supply of oxygen, the rapid airflow would have been an effective cooling mechanism, which is essential for animals that are active but too large to get rid of all the excess heat through their skin. (Dell Vostro A860 battery)

Origin of birds

Main article: Origin of birds

The possibility that dinosaurs were the ancestors of birds was first suggested in 1868 by Thomas Henry Huxley.[98] After the work of Gerhard Heilmann in the early 20th century, the theory of birds as dinosaur descendants was abandoned in favor of the idea of their being descendants of generalized thecodonts(Dell Inspiron Mini 1012 battery), with the key piece of evidence being the supposed lack of clavicles in dinosaurs.[99] However, as later discoveries showed, clavicles (or a single fused wishbone, which derived from separate clavicles) were not actually absent;[13] they had been found as early as 1924 in Oviraptor, but misidentified as an interclavicle.[100] In the 1970s, John Ostrom revived the dinosaur–bird theory, (Sony VGN-NR11Z Battery) which gained momentum in the coming decades with the advent of cladistic analysis,[102] and a great increase in the discovery of small theropods and early birds.[21] Of particular note have been the fossils of the Yixian Formation, where a variety of theropods and early birds have been found, often with feathers of some type.[13] Birds share over a hundred distinct anatomical features with theropod dinosaurs(Sony VGN-NR11S Battery), which are now generally accepted to have been their closest ancient relatives.[103] They are most closely allied with maniraptoran coelurosaurs.[13] A minority of scientists, most notably Alan Feduccia and Larry Martin, have proposed other evolutionary paths, including revised versions of Heilmann's basal archosaur proposal,[104] or that maniraptoran theropods are the ancestors of birds but themselves are not dinosaurs, only convergent with dinosaurs. (Sony VGN-CR11Z Battery)

Feathers

Main article: Feathered dinosaurs

The famous Berlin Specimen of Archaeopteryx lithographica

Archaeopteryx was the first fossil found which revealed a potential connection between dinosaurs and birds. It is considered a transitional fossil, in that it displays features of both groups. Brought to light just two years after Darwin's seminal The Origin of Species, its discovery spurred the nascent debate between proponents of evolutionary biology and creationism(Sony VGN-CR11S Battery). This early bird is so dinosaur-like that, without a clear impression of feathers in the surrounding rock, at least one specimen was mistaken for Compsognathus.[106]

Since the 1990s, a number of additional feathered dinosaurs have been found, providing even stronger evidence of the close relationship between dinosaurs and modern birds. Most of these specimens were unearthed in the lagerstätte of the Yixian Formation(Sony VGN-CR11M Battery), Liaoning, northeastern China, which was part of an island continent during the Cretaceous. Though feathers have been found in only a few locations, it is possible that non-avian dinosaurs elsewhere in the world were also feathered. The lack of widespread fossil evidence for feathered non-avian dinosaurs may be because delicate features like skin and feathers are not often preserved by fossilization and thus are absent from the fossil record(Sony VGN-CR11E Battery). To this point, protofeathers (thin, filament-like structures) are known from dinosaurs at the base of Coelurosauria, such as compsognathids like Sinosauropteryx and tyrannosauroids (Dilong),[107] but barbed feathers are known only among the coelurosaur subgroup Maniraptora, which includes oviraptorosaurs, troodontids, dromaeosaurids, and birds.[13][108] The description of feathered dinosaurs has not been without controversy(Sony VGN-CR21E Battery); perhaps the most vocal critics have been Alan Feduccia and Theagarten Lingham-Soliar, who have proposed that protofeathers are the result of the decomposition of collagenous fiber that underlaid the dinosaurs' integument, and that maniraptoran dinosaurs with barbed feathers were not actually dinosaurs, but convergent with dinosaurs(Sony VGN-CR21S Battery). However, their views have for the most part not been accepted by other researchers, to the point that the question of the scientific nature of Feduccia's proposals has been raised.[112]

Skeleton

Because feathers are often associated with birds, feathered dinosaurs are often touted as the missing link between birds and dinosaurs. However, the multiple skeletal features also shared by the two groups represent another important line of evidence for paleontologists(Sony VGN-CR21Z Battery). Areas of the skeleton with important similarities include the neck, pubis, wrist (semi-lunate carpal), arm and pectoral girdle, furcula (wishbone), and breast bone. Comparison of bird and dinosaur skeletons through cladistic analysis strengthens the case for the link.

Soft anatomy

Pneumatopores on the left ilium of Aerosteon riocoloradensis

Large meat-eating dinosaurs had a complex system of air sacs similar to those found in modern birds, according to an investigation which was led by Patrick O'Connor of Ohio University(Sony VGN-CR31S Battery). The lungs of theropod dinosaurs (carnivores that walked on two legs and had bird-like feet) likely pumped air into hollow sacs in their skeletons, as is the case in birds. "What was once formally considered unique to birds was present in some form in the ancestors of birds", O'Connor said.[113] In a 2008 paper published in the online journal PLoS ONE, scientists described Aerosteon riocoloradensis(Sony VGN-CR31E Battery), the skeleton of which supplies the strongest evidence to date of a dinosaur with a bird-like breathing system. CT-scanning of Aerosteon's fossil bones revealed evidence for the existence of air sacs within the animal's body cavity.

Behavioral evidence

Fossils of the troodonts Mei and Sinornithoides demonstrate that some dinosaurs slept with their heads tucked under their arms. This behavior, which may have helped to keep the head warm, is also characteristic of modern birds(Sony VGN-CR31Z Battery). Several deinonychosaur and oviraptorosaur specimens have also been found preserved on top of their nests, likely brooding in a bird-like manner.[117] The ratio between egg volume and body mass of adults among these dinosaurs suggest that the eggs were primarily brooded by the male, and that the young were highly precocial, similar to many modern ground-dwelling birds. (Sony VGN-CR41Z Battery)

Some dinosaurs are known to have used gizzard stones like modern birds. These stones are swallowed by animals to aid digestion and break down food and hard fibers once they enter the stomach. When found in association with fossils, gizzard stones are called gastroliths.[119]

Extinction of major groups

Main article: Cretaceous–Paleogene extinction event

The discovery that birds are a type of dinosaur showed that dinosaurs in general are not, in fact, extinct as is commonly stated. (Sony VGN-CR41S Battery) However, all non-avian dinosaurs as well as many groups of birds did suddenly become extinct approximately 65 million years ago. Many other groups of animals also became extinct at this time, including ammonites (nautilus-like mollusks), mosasaurs, plesiosaurs, pterosaurs, and many groups of mammals. (Sony VGN-CR41E Battery)This mass extinction is known as the Cretaceous–Paleogene extinction event. The nature of the event that caused this mass extinction has been extensively studied since the 1970s; at present, several related theories are supported by paleontologists. Though the consensus is that an impact event was the primary cause of dinosaur extinction(Sony VGN-CR41SR Battery), some scientists cite other possible causes, or support the idea that a confluence of several factors was responsible for the sudden disappearance of dinosaurs from the fossil record.

At the peak of the Mesozoic, there were no polar ice caps, and sea levels are estimated to have been from 100 to 250 meters (300 to 800 ft) higher than they are today. The planet's temperature was also much more uniform, with only 25 °C (45 °F) separating average polar temperatures from those at the equator(Sony VGN-CR42Z Battery). On average, atmospheric temperatures were also much higher; the poles, for example, were 50 °C (90 °F) warmer than today.

The atmosphere's composition during the Mesozoic is a matter for debate. While some academics argue that oxygen levels were much higher than today, others argue that biological adaptations seen in birds and dinosaurs indicate that respiratory systems evolved beyond what would be necessary if oxygen levels were high. (Sony VGN-CR42S Battery) By the late Cretaceous, the environment was changing dramatically. Volcanic activity was decreasing, which led to a cooling trend as levels of atmospheric carbon dioxide dropped. Oxygen levels in the atmosphere also started to fluctuate and would ultimately fall considerably. Some scientists hypothesize that climate change, combined with lower oxygen levels(Sony VGN-CR42E Battery), might have led directly to the demise of many species. If the dinosaurs had respiratory systems similar to those commonly found in modern birds, it may have been particularly difficult for them to cope with reduced respiratory efficiency, given the enormous oxygen demands of their very large bodies. (Sony Vaio VGN-CR11S/L Battery)

Impact event

Main article: Chicxulub crater

The Chicxulub Crater at the tip of the Yucatán Peninsula; the impactor that formed this crater may have caused the dinosaur extinction.

The asteroid collision theory, which was brought to wide attention in 1980 by Walter Alvarez and colleagues, links the extinction event at the end of the Cretaceous period to a bolide impact approximately 65.5 million years ago(Sony Vaio VGN-CR11S/P Battery). Alvarez et al. proposed that a sudden increase in iridium levels, recorded around the world in the period's rock stratum, was direct evidence of the impact.[124] The bulk of the evidence now suggests that a bolide 5 to 15 kilometers (3 to 9 mi) wide hit in the vicinity of the Yucatán Peninsula (in southeastern Mexico), creating the approximately 180 km (110 mi) Chicxulub Crater and triggering the mass extinction. (Sony Vaio VGN-CR11S/W Battery) Scientists are not certain whether dinosaurs were thriving or declining before the impact event. Some scientists propose that the meteorite caused a long and unnatural drop in Earth's atmospheric temperature, while others claim that it would have instead created an unusual heat wave. The consensus among scientists who support this theory is that the impact caused extinctions both directly(Sony Vaio VGN-CR11Z/R Battery) (by heat from the meteorite impact) and also indirectly (via a worldwide cooling brought about when matter ejected from the impact crater reflected thermal radiation from the sun). Although the speed of extinction cannot be deduced from the fossil record alone, various models suggest that the extinction was extremely rapid, being down to hours rather than years. (Sony Vaio VGN-CR13/B Battery)

In September 2007, U.S. researchers led by William Bottke of the Southwest Research Institute in Boulder, Colorado, and Czech scientists used computer simulations to identify the probable source of the Chicxulub impact. They calculated a 90% probability that a asteroid named Baptistina, approximately 160 km (99 mi) in diameter(Sony Vaio VGN-CR13/L Battery), orbiting in the asteroid belt which lies between Mars and Jupiter, was struck by a smaller unnamed asteroid about 55 km (35 mi) in diameter about 160 million years ago. The impact shattered Baptistina, creating a cluster which still exists today as the Baptistina family. Calculations indicate that some of the fragments were sent hurtling into earth-crossing orbits(Sony Vaio VGN-CR13/P Battery), one of which was the 10 km (6.2 mi) wide meteorite which struck Mexico's Yucatan peninsula 65 million years ago, creating the Chicxulub crater.[128] In 2011, new data from the Wide-field Infrared Survey Explorer revised the date of the collision which created the Baptistina family to about 80 million years ago. This makes an asteroid from this family highly improbable to be the asteroid that created the Chicxulub Crater(Sony Vaio VGN-CR13/R Battery), as typically the process of resonance and collision of an asteroid takes many tens of millions of years.[129]

A similar but more controversial explanation proposes that "passages of the [hypothetical] solar companion star Nemesis through the Oort comet cloud would trigger comet showers."[130] One or more of these comets then collided with the Earth at approximately the same time, causing the worldwide extinction. As with the impact of a single asteroid(Sony Vaio VGN-CR13/W Battery), the end result of this comet bombardment would have been a sudden drop in global temperatures, followed by a protracted cool period.[130]

Deccan Traps

Main article: Deccan Traps

Before 2000, arguments that the Deccan Traps flood basalts caused the extinction were usually linked to the view that the extinction was gradual, as the flood basalt events were thought to have started around 68 million years ago and lasted for over 2 million years(Sony Vaio VGN-CR13G Battery). However, there is evidence that two thirds of the Deccan Traps were created in only 1 million years about 65.5 million years ago, and so these eruptions would have caused a fairly rapid extinction, possibly over a period of thousands of years, but still longer than would be expected from a single impact event.

The Deccan Traps could have caused extinction through several mechanisms, including the release into the air of dust and sulphuric aerosols(Sony Vaio VGN-CR13G/B Battery), which might have blocked sunlight and thereby reduced photosynthesis in plants. In addition, Deccan Trap volcanism might have resulted in carbon dioxide emissions, which would have increased the greenhouse effect when the dust and aerosols cleared from the atmosphere.[132] Before the mass extinction of the dinosaurs, the release of volcanic gases during the formation of the Deccan Traps "contributed to an apparently massive global warming(Sony Vaio VGN-CR13G/L Battery). Some data point to an average rise in temperature of 8 °C (14 °F) in the last half million years before the impact [at Chicxulub]."

In the years when the Deccan Traps theory was linked to a slower extinction, Luis Alvarez (who died in 1988) replied that paleontologists were being misled by sparse data. While his assertion was not initially well-received, later intensive field studies of fossil beds lent weight to his claim(Sony Vaio VGN-CR13G/W Battery). Eventually, most paleontologists began to accept the idea that the mass extinctions at the end of the Cretaceous were largely or at least partly due to a massive Earth impact. However, even Walter Alvarez has acknowledged that there were other major changes on Earth even before the impact, such as a drop in sea level and massive volcanic eruptions that produced the Indian Deccan Traps, and these may have contributed to the extinctions. (Sony Vaio VGN-CR13G/P Battery)

Failure to adapt to changing conditions

Lloyd et al. (2008) noted that, in the Mid Cretaceous, the flowering, angiosperm plants became a major part of terrestrial ecosystems, which had previously been dominated by gymnosperms such as conifers. Dinosaur coprolite–fossilized dung–indicate that, while some ate angiosperms, most herbivorous dinosaurs ate mainly gymnosperms(Sony Vaio VGN-CR13G/R Battery). Statistical analysis by Lloyd et al. concluded that, contrary to earlier studies, dinosaurs did not diversify very much in the Late Cretaceous. Lloyd et al. suggested that dinosaurs' failure to diversify as ecosystems were changing doomed them to extinction.[134]

Possible Paleocene survivors

Main article: Paleocene dinosaurs

Non-avian dinosaur remains are occasionally found above the Cretaceous–Paleogene boundary. In 2001, paleontologists Zielinski and Budahn reported the discovery of a single hadrosaur leg-bone fossil in the San Juan Basin(Sony Vaio VGN-CR13T/L Battery), New Mexico, and described it as evidence of Paleocene dinosaurs. The formation in which the bone was discovered has been dated to the early Paleocene epoch, approximately 64.5 million years ago. If the bone was not re-deposited into that stratum by weathering action, it would provide evidence that some dinosaur populations may have survived at least a half million years into the Cenozoic Era. (Sony Vaio VGN-CR13T/P Battery)Other evidence includes the finding of dinosaur remains in the Hell Creek Formation up to 1.3 meters (51 in) above (40000 years later than) the Cretaceous–Paleogene boundary. Similar reports have come from other parts of the world, including China.[136] Many scientists, however, dismissed the supposed Paleocene dinosaurs as re-worked(Sony Vaio VGN-CR13T/R Battery), that is, washed out of their original locations and then re-buried in much later sediments. However, direct dating of the bones themselves has supported the later date, with U–Pb dating methods resulting in a precise age of 64.8 ± 0.9 million years ago.[139] If correct, the presence of a handful of dinosaurs in the early Paleocene would not change the underlying facts of the extinction. (Sony Vaio VGN-CR13T/W Battery)

History of study

Further information: History of paleontology

Dinosaur fossils have been known for millennia, although their true nature was not recognized. The Chinese, whose modern word for dinosaur is konglong (恐龍, or "terrible dragon"), considered them to be dragon bones and documented them as such. For example, Hua Yang Guo Zhi, a book written by Zhang Qu during the Western Jin Dynasty(Sony Vaio VGN-CR150E/B Battery), reported the discovery of dragon bones at Wucheng in Sichuan Province.[140] Villagers in central China have long unearthed fossilized "dragon bones" for use in traditional medicines, a practice that continues today.[141] In Europe, dinosaur fossils were generally believed to be the remains of giants and other creatures killed by the Great Flood(Sony Vaio VGN-CR21/B Battery).

Marsh's 1896 illustration of the bones of Stegosaurus, a dinosaur he described and named in 1877.

Scholarly descriptions of what would now be recognized as dinosaur bones first appeared in the late 17th century in England. Part of a bone, now known to have been the femur of a Megalosaurus, (Sony Vaio VGN-CR21E/L Battery) was recovered from a limestone quarry at Cornwell near Chipping Norton, Oxfordshire, England, in 1676. The fragment was sent to Robert Plot, Professor of Chemistry at the University of Oxford and first curator of the Ashmolean Museum, who published a description in his Natural History of Oxfordshire in 1677. He correctly identified the bone as the lower extremity of the femur of a large animal(Sony Vaio VGN-CR21E/P Battery), and recognized that it was too large to belong to any known species. He therefore concluded it to be the thigh bone of a giant human similar to those mentioned in the Bible. In 1699, Edward Lhuyd, a friend of Sir Isaac Newton, was responsible for the first published scientific treatment of what would now be recognized as a dinosaur when he described and named a sauropod tooth(Sony Vaio VGN-CR21E/W Battery), "Rutellum implicatum", that had been found in Caswell, near Witney, Oxfordshire.[145]

William Buckland

Between 1815 and 1824, the Rev William Buckland, a professor of geology at Oxford University, collected more fossilized bones of Megalosaurus and became the first person to describe a dinosaur in a scientific journal. (Sony Vaio VGN-CR21S/L Battery) The second dinosaur genus to be identified, Iguanodon, was discovered in 1822 by Mary Ann Mantell – the wife of English geologist Gideon Mantell. Gideon Mantell recognized similarities between his fossils and the bones of modern iguanas. He published his findings in 1825.

The study of these "great fossil lizards" soon became of great interest to European and American scientists, and in 1842 the English paleontologist Richard Owen coined the term "dinosaur"(Sony Vaio VGN-CR21S/P Battery). He recognized that the remains that had been found so far, Iguanodon, Megalosaurus and Hylaeosaurus, shared a number of distinctive features, and so decided to present them as a distinct taxonomic group. With the backing of Prince Albert of Saxe-Coburg-Gotha, the husband of Queen Victoria, Owen established the Natural History Museum in South Kensington(Sony Vaio VGN-CR21S/W Battery), London, to display the national collection of dinosaur fossils and other biological and geological exhibits.

In 1858, the first known American dinosaur was discovered, in marl pits in the small town of Haddonfield, New Jersey (although fossils had been found before, their nature had not been correctly discerned). The creature was named Hadrosaurus foulkii(Sony Vaio VGN-CR21Z/N Battery). It was an extremely important find: Hadrosaurus was one of the first nearly complete dinosaur skeletons found (the first was in 1834, in Maidstone, Kent, England), and it was clearly a bipedal creature. This was a revolutionary discovery as, until that point, most scientists had believed dinosaurs walked on four feet, like other lizards. Foulke's discoveries sparked a wave of dinosaur mania in the United States(Sony Vaio VGN-CR21Z/R Battery).

Othniel Charles Marsh, 19th century photograph

Edward Drinker Cope, 19th century photograph

Dinosaur mania was exemplified by the fierce rivalry between Edward Drinker Cope and Othniel Charles Marsh, both of whom raced to be the first to find new dinosaurs in what came to be known as the Bone Wars. The feud probably originated when Marsh publicly pointed out that Cope's reconstruction of an Elasmosaurus skeleton was flawed(Sony Vaio VGN-CR23/B Battery): Cope had inadvertently placed the plesiosaur's head at what should have been the animal's tail end. The fight between the two scientists lasted for over 30 years, ending in 1897 when Cope died after spending his entire fortune on the dinosaur hunt. Marsh 'won' the contest primarily because he was better funded through a relationship with the US Geological Survey. Unfortunately(Sony Vaio VGN-CR23/P Battery), many valuable dinosaur specimens were damaged or destroyed due to the pair's rough methods: for example, their diggers often used dynamite to unearth bones (a method modern paleontologists would find appalling). Despite their unrefined methods, the contributions of Cope and Marsh to paleontology were vast: Marsh unearthed 86 new species of dinosaur and Cope discovered 56, a total of 142 new species(Sony Vaio VGN-CR23/R Battery). Cope's collection is now at the American Museum of Natural History in New York, while Marsh's is on display at the Peabody Museum of Natural History at Yale University.[149]

After 1897, the search for dinosaur fossils extended to every continent, including Antarctica. The first Antarctic dinosaur to be discovered, the ankylosaurid Antarctopelta oliveroi, was found on Ross Island in 1986, although it was 1994 before an Antarctic species, the theropod Cryolophosaurus ellioti, was formally named and described in a scientific journal(Sony Vaio VGN-CR23/L Battery).

Current dinosaur "hot spots" include southern South America (especially Argentina) and China. China in particular has produced many exceptional feathered dinosaur specimens due to the unique geology of its dinosaur beds, as well as an ancient arid climate particularly conducive to fossilization(Sony Vaio VGN-CR23/N Battery).

The "dinosaur renaissance"

Main article: Dinosaur renaissance

Paleontologist Robert T. Bakker with mounted skeleton of a tyrannosaurid (Gorgosaurus libratus)

The field of dinosaur research has enjoyed a surge in activity that began in the 1970s and is ongoing. This was triggered, in part, by John Ostrom's discovery of Deinonychus, an active predator that may have been warm-blooded(Sony Vaio VGN-CR23/W Battery), in marked contrast to the then-prevailing image of dinosaurs as sluggish and cold-blooded. Vertebrate paleontology has become a global science. Major new dinosaur discoveries have been made by paleontologists working in previously unexploited regions, including India, South America, Madagascar, Antarctica, and most significantly China (Sony VAIO VGN-NW21EF/S battery) (the amazingly well-preserved feathered dinosaurs in China have further consolidated the link between dinosaurs and their conjectured living descendants, modern birds). The widespread application of cladistics, which rigorously analyzes the relationships between biological organisms, has also proved tremendously useful in classifying dinosaurs(Sony VAIO VGN-NW21JF battery). Cladistic analysis, among other modern techniques, helps to compensate for an often incomplete and fragmentary fossil record.

Soft tissue and DNA

One of the best examples of soft-tissue impressions in a fossil dinosaur was discovered in Petraroia, Italy. The discovery was reported in 1998, and described the specimen of a small, very young coelurosaur, Scipionyx samniticus. The fossil includes portions of the intestines, colon, liver, muscles, and windpipe of this immature dinosaur. (Sony VAIO VGN-NW21MF battery)

In the March 2005 issue of Science, the paleontologist Mary Higby Schweitzer and her team announced the discovery of flexible material resembling actual soft tissue inside a 68-million-year-old Tyrannosaurus rex leg bone from the Hell Creek Formation in Montana. After recovery, the tissue was rehydrated by the science team. (Sony VAIO VGN-NW21MF/W battery)

When the fossilized bone was treated over several weeks to remove mineral content from the fossilized bone-marrow cavity (a process called demineralization), Schweitzer found evidence of intact structures such as blood vessels, bone matrix, and connective tissue (bone fibers). Scrutiny under the microscope further revealed that the putative dinosaur soft tissue had retained fine structures (microstructures) (Sony VAIO VGN-NW31EF/W battery) even at the cellular level. The exact nature and composition of this material, and the implications of Schweitzer's discovery, are not yet clear; study and interpretation of the material is ongoing.[43]

The successful extraction of ancient DNA from dinosaur fossils has been reported on two separate occasions, but, upon further inspection and peer review, neither of these reports could be confirmed. (Sony VAIO VGN-NW21ZF battery) However, a functional visual peptide of a theoretical dinosaur has been inferred using analytical phylogenetic reconstruction methods on gene sequences of related modern species such as reptiles and birds.[151] In addition, several proteins, including hemoglobin,[152] have putatively been detected in dinosaur fossils.[153][154]

Cultural depictions(Sony VAIO VGN-NW31JF battery)

Main article: Cultural depictions of dinosaurs

Outdated Iguanodon statues created by Benjamin Waterhouse Hawkins for the Crystal Palace Park in 1853.

By human standards, dinosaurs were creatures of fantastic appearance and often enormous size. As such, they have captured the popular imagination and become an enduring part of human culture. Entry of the word "dinosaur" into the common vernacular reflects the animals' cultural importance(Sony VAIO VGN-NW320F/B battery): in English, "dinosaur" is commonly used to describe anything that is impractically large, obsolete, or bound for extinction.[155]

Public enthusiasm for dinosaurs first developed in Victorian England, where in 1854, three decades after the first scientific descriptions of dinosaur remains, the famous dinosaur sculptures were unveiled in London's Crystal Palace Park(Sony VAIO VGN-NW320F/TC battery). The Crystal Palace dinosaurs proved so popular that a strong market in smaller replicas soon developed. In subsequent decades, dinosaur exhibits opened at parks and museums around the world, ensuring that successive generations would be introduced to the animals in an immersive and exciting way.[156] Dinosaurs' enduring popularity, in its turn(Sony VAIO VGN-NW35e battery), has resulted in significant public funding for dinosaur science, and has frequently spurred new discoveries. In the United States, for example, the competition between museums for public attention led directly to the Bone Wars of the 1880s and 1890s, during which a pair of feuding paleontologists made enormous scientific contributions. (Sony VAIO VGN-NW11S/S battery)

The popular preoccupation with dinosaurs has ensured their appearance in literature, film, and other media. Beginning in 1852 with a passing mention in Charles Dickens' Bleak House,[158] dinosaurs have been featured in large numbers of fictional works. Sir Arthur Conan Doyle's 1912 book The Lost World, the iconic 1933 film King Kong, the 1954 Godzilla and its many sequels(Sony VAIO VGN-NW11Z/S battery), the best-selling 1990 novel Jurassic Park by Michael Crichton and its 1993 film adaptation are just a few notable examples of dinosaur appearances in fiction. Authors of general-interest non-fiction works about dinosaurs, including some prominent paleontologists, have often sought to use the animals as a way to educate readers about science in general(Sony VAIO VGN-NW11S/T battery). Dinosaurs are ubiquitous in advertising; numerous companies have referenced dinosaurs in printed or televised advertisements, either in order to sell their own products or in order to characterize their rivals as slow-moving, dim-witted, or obsolete.[159] Even fine artists have featured dinosaurs in their works(Sony VAIO VGN-NW11Z/T battery).

Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct. Three living species of elephant are recognized: the African bush elephant, the African forest elephant and the Indian or Asian elephantSony VAIO PCG-8131M battery; although some group the two African species into one and some researchers also postulate the existence of a fourth species in West Africa. All other species and genera of Elephantidae are extinct. Most have been extinct since the last ice age, although dwarf forms of mammoths might have survived as late as 2,000 BCE. Elephants and other Elephantidae were once classified with other thick-skinned animals in a now invalid order, PachydermataSony VAIO PCG-8152M battery.

Elephants are the largest living land animals on Earth today. The elephant's gestation period is 22 months, the longest of any land animal. At birth, an elephant calf typically weighs 105 kilograms (230 lb). They typically live for 50 to 70 years, but the oldest recorded elephant lived for 82 years. The largest elephant ever recorded was shot in Angola in 1955Sony VAIO PCG-31311M battery. This male weighed about 10,900 kg (24,000 lb), with a shoulder height of 3.96 metres (13.0 ft), 1 metre (3.3 ft) taller than the average male African elephant. The smallest elephants, about the size of a calf or a large pig, were a prehistoric species that lived on the island of Crete during the Pleistocene epochSony VAIO PCG-31111M battery.

Elephants are a symbol of wisdom in Asian cultures and are famed for their memory and intelligence; their intelligence level is thought to be comparable to that of dolphins and primates. Aristotle once said the elephant was "the beast which passeth all others in wit and mind." The word "elephant" has its origins in the Greek ἐλέφας, meaning "ivory" or "elephant"Sony VAIO PCG-8112M battery.

Healthy adult elephants have no natural predators, although lions may take calves or weak individuals. They are, however, threatened by human intrusion and poaching.

Etymology

Olifant and its variations (ex. oliphant, olyphant) are archaic spellings of elephant. Aside from elephants, the word has been used to refer to ivory, elephant tusks, musical horns made of elephant tusks, or a musical instrument resembling such hornsSony VAIO PCG-7186M battery.

It appears in Middle English as olifant or olifaunt, and was borrowed from Medieval French olifanz. The French word owes something to both Old High German olbenta "camel", and to Latin elephantus "elephant", a word of Greek origin. OHG olbenta is a word of old Germanic origin; cf. Gothic ulbandus also meaning "camel". But the form of the OHG and Gothic words suggests it is also a borrowingSony VAIO PCG-7171M battery, perhaps indeed directly or indirectly from Greek "ἐλέφας" (elephas), which in Homer only meant "ivory", but from Herodotus on the word also referred to the animal. The earliest attested form of the word is the Mycenaean Greek e-re-pa-to, written in Linear B syllabic script.

Taxonomy and evolution

The African elephant genus contains two living species; whereas the Asian elephant species is the only surviving member of the Asian elephant genusSony VAIO PCG-9Z1M battery, but can be divided into four subspecies. The African and the Asian elephants diverged from a common ancestor some 7.6 million years ago.

African elephant

Main articles: African elephant, African bush elephant, and African forest elephant

Elephant crossing a river, Kenya.

African bush (savanna) elephant in Etosha National Park, Namibia.

Video of elephants in the wild

The elephants of the genus Loxodonta, known collectively as African elephants, are currently found in 37 countries in Africa.

African elephants are distinguished from Asian elephants in several ways, the most noticeable being their much larger earsSony VAIO PCG-5S1M battery. Also, the African elephant is typically larger than the Asian elephant and has a concave back. In Asian elephants, only males have tusks, but both males and females of African elephants have tusks and are usually less hairy than their Asian cousins.

African elephants have traditionally been classified as a single species comprising two distinct subspecies, namely the savanna elephant (Loxodonta africana africana) and the forest elephant (Loxodonta africana cyclotis) Sony VAIO PCG-5P1M battery, but recent DNA analysis suggests that these may actually constitute distinct species. This split is not universally accepted by experts. A third species of African elephant has also been proposed.

The authors of an analysis of nuclear DNA extracted from "African savanna elephant, African forest elephant, Asian elephant, the extinct American mastodon, and the woolly mammoth" concluded in 2010 that African savanna and forest elephants are indeed separate speciesSony VAIO PCG-5N2M battery:

We unequivocally establish that the Asian elephant is the sister species to the woolly mammoth. A surprising finding from our study is that the divergence of African savanna and forest elephants—which some have argued to be two populations of the same species—is about as ancient as the divergence of Asian elephants and mammothsSony VAIO PCG-3C2M battery. Given their ancient divergence, we conclude that African savanna and forest elephants should be classified as two distinct species.

This reclassification has implications for conservation. If there are two separate species, each will be less abundant (particularly the rarer) and could be more endangered than a more numerous and wide-ranging single species. There is also a potential danger that if the forest elephant is not explicitly listed as an endangered speciesSony VAIO PCG-8161M battery, poachers and smugglers might be able to evade the law forbidding trade in endangered animals and their products.

The forest elephant and the savanna elephant can hybridize (interbreed), though their preferences for different terrains reduce such opportunities. As the African elephant has only recently been recognized to comprise two separate species, groups of captive elephants have not been comprehensively classified and some could well be hybridsSony VAIO PCG-8141M battery.

Under the new two species classification, Loxodonta africana refers specifically to the savanna elephant, the largest of all elephants. It is the largest land animal, with males standing 3.2 metres (10 ft) to 4 metres (13 ft) at the shoulder and weighing 3,500 kilograms (7,700 lb) up to a reported 12,000 kilograms (26,000 lb). The female is smaller, standing about 3 metres (9.8 ft) at the shoulder. Sony VAIO PCG-3J1M battery Most often, savanna elephants are found in open grasslands, marshes, and lakeshores. They range over much of the savanna zone south of the Sahara.

The other putative species, the forest elephant (Loxodonta cyclotis), is usually smaller and rounder, and its tusks thinner and straighter compared with the savanna elephant. The forest elephant can weigh up to 4,500 kilograms (9,900 lb) and stand about 3 metres (10 ft) tall. Much less is known about these animals than their savanna cousinsSony VAIO PCG-3H1M battery, because environmental and political obstacles make them difficult to study. Normally, they inhabit the dense African rain forests of central and western Africa, although occasionally they roam the edges of forests, thus overlapping the savanna elephant home ranges and hybridizing. In 1979, Iain Douglas-Hamilton estimated the continental population of African elephants at around 1.3 million animals. Sony VAIO PCG-3F1M battery This estimate is controversial and is believed to be a gross overestimate,[34] but it is very widely cited and has become a de facto baseline that continues to be incorrectly used to quantify downward population trends in the species. Through the 1980s, Loxodonta received worldwide attention due to the dwindling numbers of major populations in East Africa, largely as a result of poachingSony VAIO PCG-3C1M battery. According to IUCN’s African Elephant Status Report 2007,[35] there are between 470,000 and 690,000 African elephants in the wild. Although this estimate only covers about half of the total elephant range, experts do not believe the true figure to be much higher, as it is unlikely that large populations remain to be discovered.[36] By far, the largest populations are now found in southern and eastern AfricaSony VAIO PCG-9Z2L battery, which together account for the majority of the continental population. According to a recent analysis by IUCN experts, most major populations in eastern and southern Africa are stable or have been steadily increasing since the mid-1990s, at an average rate of 4.5% per year.[36][37]

Elephant populations in West Africa, on the other hand, are generally small and fragmented, and only account for a small proportion of the continental total. Sony VAIO PCG-9Z1L battery Much uncertainty remains as to the size of the elephant population in central Africa, where the prevalence of forest makes population surveys difficult, but poaching for ivory and bushmeat is believed to be intense through much of the region.[39] South African elephant population more than doubled, rising from 8,000 to over 20,000Sony VAIO PCG-9131L battery, in the thirteen years after a 1995 ban on the trade in elephant ivory.[40] The ban on the ivory trade in southern Africa (but not elsewhere) was lifted in February 2008, sparking controversy among environmental groups.[citation needed]

Asian elephant

Main article: Asian elephant

The Asian elephant, Elephas maximus, is smaller than the African. It has smaller ears, and typically, only the males have large external tusksSony VAIO PCG-8161L battery.

The world population of Asian elephants—also called Indian elephants—is estimated to be around 60,000, about a tenth of the number of African elephants. More precisely, it is estimated that there are between 38,000 and 53,000 wild elephants and between 14,500 and 15,300 domesticated elephants in Asia, with perhaps another 1,000 scattered around zoos in the rest of the world. Sony VAIO PCG-8152L battery The Asian elephants' decline has possibly been more gradual than the African and caused primarily by poaching and habitat destruction by human encroachment.

A decorated Indian elephant in Jaipur, India.

Elephant orphanage in Sri Lanka

Several subspecies of Elephas maximus have been identified, using morphometric data and molecular markers. Elephas maximus maximus (Sri Lankan elephant) is found only on the island of Sri Lanka. It is the largest of the AsiansSony VAIO PCG-8141L battery. There are an estimated 3,000–4,500 members of this subspecies left today in the wild, although no accurate census has been carried out recently. Large males can weigh upward to 5,400 kg (12,000 lb) and stand over 3.4 m (11 ft) tall. Sri Lankan males have very large cranial bulges, and both sexes have more areas of depigmentation than other Asians. Typically, their ears, face, trunk, and belly have large concentrations of pink-speckled skinSony VAIO PCG-8131L battery. There is an orphanage for elephants in Pinnawala, Sri Lanka, which plays a large role in protecting the Sri Lankan elephant from extinction.

Elephas maximus indicus (Indian elephant) makes up the bulk of the Asian elephant population. Numbering approximately 36,000, these elephants are lighter grey in colour, with depigmentation only on the ears and trunkSony VAIO PCG-81312L battery. Large males will ordinarily weigh only about 5,000 kg (11,000 lb), but are as tall as the Sri Lankan. The mainland Asian can be found in 11 Asian countries, from India to Indonesia. They prefer forested areas and transitional zones, between forests and grasslands, where greater food variety is available.

The Sumatran elephant, Elephas maximus sumatranus, found only on SumatraSony VAIO PCG-81214L battery, is smaller than the Indian elephant. Population estimates for this group range from 2,100 to 3,000 individuals. It is very light grey in colour and has less depigmentation than the other Asians, with pink spots only on the ears. Mature Sumatrans will usually only measure 1.7–2.6 m (5.6–8.5 ft) at the shoulder and weigh less than 3,000 kg (6,600 lb). It is considerably smaller than its other Asian (and African) cousins and exists only on the island of Sumatra, usually in forested regions and partially wooded habitatsSony VAIO PCG-81115L battery.

In 2003, a further subspecies was identified on Borneo. Named the Borneo pygmy elephant, it is smaller and tamer than any other Asian elephants. It also has relatively larger ears, longer tail and straighter tusks.

Physical characteristics

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TrunkSony VAIO PCG-81114L battery

The elephant raises its trunk as a sign of warning or to smell enemies or friends

Articulation of elephant trunk.

An elephant can use its trunk for a variety of purposes. This one is wiping its eye.

Eye of an Asian elephant.

The proboscis, or trunk, is a fusion of the nose and upper lip,[42] elongated and specialized to become the elephant's most important and versatile appendage. African elephants are equipped with two fingerlike projections at the tip of their trunk, while Asians have only oneSony VAIO PCG-81114L battery. The elephant's trunk is sensitive enough to pick up a single blade of grass, yet strong enough to rip the branches off a tree.

Most herbivores (plant eaters, like the elephant) possess teeth adapted for cutting and tearing off plant materials. However, except for the very young or infirm, elephants always use their trunks to tear up their food and then place it in their mouths. They will graze on grass or reach up into trees to grasp leaves, fruit, or entire branchesSony VAIO PCG-81113L battery. If the desired food item is too high up, the elephant will wrap its trunk around the tree or branch and shake its food loose or sometimes simply knock the tree down altogether.

The trunk is also used for drinking. Elephants suck water up into the trunk—up to 14 litres (15 quarts) at a time—and then blow it into their mouths. Elephants also suck up water to spray on their bodies during bathingSony VAIO PCG-7142L battery. On top of this watery coating, the animals will then spray dirt and mud, which dries and acts as a protective sunscreen. When swimming, the trunk makes an excellent snorkel.

This appendage also plays a key role in many social interactions. Familiar elephants will greet each other by entwining their trunks, much like a handshake. They also use them while play-wrestlingSony VAIO PCG-7141L battery, caressing during courtship and mother-child interactions, and for dominance displays; a raised trunk can be a warning or threat, while a lowered trunk can be a sign of submission. Elephants can defend themselves very well by flailing their trunks at unwanted intruders or by grasping and flinging them.

An elephant also relies on its trunk for its highly developed sense of smellSony VAIO PCG-71111L battery. By raising the trunk up in the air and swiveling it from side to side, like a periscope, it can determine the location of friends, enemies, and food sources. The complete trunk can have up to 150,000 separate muscle fascicles, giving it strength and flexibility.[45]

Some elephants have been afflicted by floppy trunk syndromeSony VAIO PCG-61411L battery.

Tusks

Tusks of African and Asian elephants.

The tusks of an elephant are its second upper incisors. Tusks grow continuously; an adult male's tusks grow about 18 cm (7 in) a year. Tusks are used to dig for water, salt, and roots; to debark trees to eat the bark; to dig into baobab trees to get at the pulp inside; and to move trees and branches when clearing a pathSony VAIO PCG-61112L battery. In addition, they are used for marking trees to establish territory, and occasionally as weapons. [46]

Like humans who are typically right- or left-handed, elephants are usually right- or left-tusked. The dominant tusk, called the master tusk, is generally shorter and more rounded at the tip from wear. [47] Both male and female African elephants have large tusks that can reach over 3 m (10 ft) in length and weigh over 90 kg (200 lb) Sony VAIO PCG-61111L battery. In the Asian species, only the males have large tusks. Female Asians have tusks which are very small or absent altogether. Asian males can have tusks as long as the much larger Africans, but they are usually much slimmer and lighter; the heaviest recorded is 39 kg (86 lb). The tusk of both species is mostly made of calcium phosphate in the form of apatiteSony VAIO PCG-5T4L battery. As a piece of living tissue, it is relatively soft (compared with other minerals such as rock), and the tusk, also known as ivory, is strongly favoured by artists for its carvability. The desire for elephant ivory has been one of the major factors in the reduction of the world's elephant population.

Some extinct relatives of elephants had tusks in their lower jaws in addition to their upper jaws, such as Gomphotherium, or only in their lower jaws, such as Deinotherium. Sony VAIO PCG-5T3L battery

Teeth

Elephants' teeth are very different from those of most other mammals. Over their lives they usually have 28 teeth. These are:

The two upper second incisors: these are the tusks.

The milk precursors of the tusks.

12 premolars, 3 in each side of each jaw.

12 molars, 3 in each side of each jaw.

Replica of an Asian elephant's molar, showing upper side.

This gives elephants a dental formula of:

Unlike most mammals, which grow baby teeth and then replace them with a single permanent set of adult teeth, elephants have cycles of tooth rotation throughout their entire lives. The tusks have milk precursors, which fall out quickly and the adult tusks are in place by one year of age, but the chewing teeth are replaced five[53] or, very rarelySony VAIO PCG-5T2L battery, six[54] times in an elephant's lifetime.

Only four chewing teeth (premolars and/or molars), one on each side of each jaw, are in primary use at any given time (or two, as one replaces the other at each location). Adult teeth do not replace milk teeth by emerging from the jaws vertically as human teeth do. Instead, new teeth grow in at the back of the mouth, pushing older teeth toward the frontSony VAIO PCG-5S3L battery, where the latter break off in pieces until they are gone. In African elephants, the first two sets of chewing teeth (premolars) are in place when an elephant is born. The first chewing tooth on each side in each jaw falls out when the elephant is about two years old. The second set of chewing teeth falls out when the elephant is about six years old. The third set is lost at 13 to 15 years of ageSony VAIO PCG-5S2L battery, and set four lasts to approximately 28 years of age. The fifth set of chewing teeth (molars) lasts until the elephant is in its early 40s. The sixth (and usually final) set must last the elephant the rest of its life. If an elephant lives to more than 60 years of age, the last set of molars is worn to stumps, and it can no longer feed properlySony VAIO PCG-5S1L battery. Moss reports a female elephant in its sixties whose final set of molars were worn smooth and about one-quarter of their original size and who survived "with extra chewing and longer feeding bouts." Abscesses of chewing teeth, as well as of tusks and jaws, are common in elephants, and may lead to premature death.

Tusks in the lower jaw are also second incisors. These grew out large in Deinotherium and some mastodons, but in modern elephants they disappear early without eruptingSony VAIO PCG-5R2L battery.

Skin

Skin of an African (left) and Asian (right) elephant.

African elephant bathing

Elephants are colloquially called pachyderms (from their original scientific classification), which means thick-skinned animals. An elephant's skin is extremely tough around most parts of its body and measures about 2.5 centimetres (1.0 in) thick. However, the skin around the mouth and inside of the ear is considerably thinnerSony VAIO PCG-5R1L battery. Normally, the skin of an Asian is covered with more hair than its African counterpart. This is most noticeable in the young. Asian calves are usually covered with a thick coat of brownish red fuzz. As they get older, this hair darkens and becomes more sparse, but it will always remain on their heads and tails.

The species of elephants are typically greyish in colour, but the Africans very often appear brown or reddish from wallowing in mud holes of colored soilSony VAIO PCG-5P4L battery. Wallowing is an important behaviour in elephant society. Not only is it important for socialization, but the mud acts as a sunscreen, protecting its skin from harsh ultraviolet radiation. Although tough, an elephant's skin is very sensitive. Without regular mud baths to protect it from burning, as well as from insect bites and moisture loss, an elephant's skin would suffer serious damageSony VAIO PCG-5P2L battery. After bathing, the elephant will usually use its trunk to blow soil on its body to help dry and bake on its new protective coat. As elephants are limited to smaller and smaller areas, there is less water available, and local herds will often come too close over the right to use these limited resources.

Wallowing also aids the skin in regulating body temperatures. Elephants have difficulty in releasing heat through the skin becauseSony VAIO PCG-5N4L battery, in proportion to their body size, they have very little of it. The ratio of an elephant's mass to the surface area of its skin is many times that of a human. Elephants have even been observed lifting up their legs to expose the soles of their feet, presumably in an effort to expose more skin to the air. Since wild elephants live in very hot climates, they must have other means of getting rid of excess heatSony VAIO PCG-5N2L battery.

Legs and feet

Elephant using its feet to crush a watermelon before eating it.

An elephant's toenail as a museum exhibit

An elephant's legs are roughly shaped like columns or pillars, as they must be to support its bulk. The elephant needs less muscular power to stand because of its straight legs and large padded feet. For this reason, an elephant can stand for very long periods of time without tiring. In fact, African elephants rarely lie down unless they are sick or wounded. Indian elephants, in contrast, lie down frequentlySony VAIO PCG-51513L battery.

The feet of an elephant are nearly round. African elephants have three nails on each hind foot, and four on each front foot. Indian elephants have four nails on each hind foot and five on each front foot. Beneath the bones of the foot is a tough, gelatinous material that acts as a cushion or shock absorber. Under the elephant's weight, the foot swellsSony VAIO PCG-51511L battery, but it gets smaller when the weight is removed. An elephant can sink deep into mud, but can pull its legs out readily because its feet become smaller when they are lifted.

Elephants swim well, but cannot trot, jump, or gallop. They do have two gaits: a walk and a faster gait that is similar to running.

In walking, the legs act as pendulums, with the hips and shoulders rising and falling while the foot is planted on the groundSony VAIO PCG-51412L battery. With no "aerial phase", the faster gait does not meet all the criteria of running, as elephants always have at least one foot on the ground. However, an elephant moving fast uses its legs much like other running animals, with the hips and shoulders falling and then rising while the feet are on the ground. In this gait, an elephant will have three feet off the ground at one timeSony VAIO PCG-51411L battery. As both of the hind feet and both of the front feet are off the ground at the same time, this gait has been likened to the hind legs and the front legs taking turns running.[57] Tests at the Thai Elephant Conservation Centre are reported to show that fast-moving elephants 'run' with their front legs, but 'walk' with their hind legs.Sony VAIO PCG-51312L battery

Although they start this "run" at only 8 km/h,[59] elephants have been reported to reach speeds up to 40 km/h (25 mph),[60] all the while using the same gait. In tests at the Thai Elephant Conservation Centre, the fastest elephants reached a top speed of 18 km/h (11 mph).[58] At this speed, most other four-legged creatures are well into a gallop, even accounting for leg lengthSony VAIO PCG-51311L battery. Spring-like kinetics could explain the difference between the motion of elephants and other animals.[61]

See also: Comparative foot morphology#Elephant foot

Ears

Difference between Asian (left) and African (right) elephant ears.

The large flapping ears of an elephant are also very important for temperature regulation. Elephant ears are made of a very thin layer of skin stretched over cartilage and a rich network of blood vessels. On hot days, elephants will flap their ears constantly, creating a slight breezeSony VAIO PCG-51211L battery. This breeze cools the surface blood vessels, and then the cooler blood gets circulated to the rest of the animal's body. The hot blood entering the ears can be cooled as much as 10 °F (6 °C) before returning to the body. Differences in the ear sizes of African and Asian elephants can be explained, in part, by their geographical distribution. Africans originated and stayed near the equatorSony VAIO PCG-41112L battery, where it is warmer. Therefore, they have bigger ears. Asians live farther north, in slightly cooler climates, and thus have smaller ears.

The ears are also used in certain displays of aggression and during the males' mating period. If an elephant wants to intimidate a predator or rival, it will spread its ears out wide to make itself look more massive and imposing. During the breeding season, males give off an odor from the musth gland located behind their eyesSony VAIO PCG-3A4L battery. Joyce Poole, a well-known elephant researcher, has theorized that the males will fan their ears in an effort to help propel this "elephant cologne" great distances.[62]

Biology and behavior

The skeleton of a dwarf elephant from the island of Crete. Dwarf elephants were present on some Mediterranean islands until about 10,000 years ago.

Evolution

The earliest known ancestors of modern-day elephants evolved about 60 million years ago. Moeritherium, the ancestor of the elephants from 37 million years ago was aquatic and had a similar lifestyle to a hippopotamus. Sony VAIO PCG-3A3L batteryBy the time of the first Gomphotherium the animal developed tusks on both jaws, upper and lower. Here the lineage seemed to split with the Dinotherium specialising in tusks on the lower jaws, while Mammoths and Mastodons like modern elephants develop tusks only on the top jaws.

Social behavior

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Elephants live in a structured social order. The social lives of male and female elephants are very different. The females spend their entire lives in tightly knit family groups made up of mothers, daughters, sisters, and aunts. These groups are led by the eldest female, or matriarch. Adult males, on the other hand, live mostly solitary livesSony VAIO PCG-3A1L battery.

The social circle of the female elephant does not end with the small family unit. In addition to encountering the local males that live on the fringes of one or more groups, the female's life also involves interaction with other families, clans, and subpopulations. Most immediate family groups range from five to fifteen adults, as well as a number of immature males and femalesSony VAIO PCG-394L battery. When a group gets too big, a few of the elder daughters will break off and form their own small group. They remain very aware of which local herds are relatives and which are not.

Elephant footprints (tire tracks for scale)

The life of the adult male is very different. As he gets older, he begins to spend more time at the edge of the herd, gradually going off on his own for hours or days at a time. Eventually, days become weeks, and somewhere around the age of fourteenSony VAIO PCG-393L battery, the mature male, or bull, sets out from his natal group for good. While males do live primarily solitary lives, they will occasionally form loose associations with other males. These groups are called bachelor herds. The males spend much more time than the females fighting for dominance with each other. Only the most dominant males will be permitted to breed with cycling femalesSony VAIO PCG-391L battery. The less dominant ones must wait their turns. It is usually the older bulls, forty to fifty years old, that do most of the breeding.

The dominance battles between males can look very fierce, but typically they inflict very little injury. Most of the bouts are in the form of aggressive displays and bluffs. Ordinarily, the smaller, younger, and less confident animal will back off before any real damage can be doneSony VAIO PCG-384L battery. However, during the breeding season, the battles can get extremely aggressive, and the occasional elephant is injured. During this season, known as musth, a bull will fight with almost any other male it encounters, and it will spend most of its time hovering around the female herds, trying to find a receptive mate.

In West with the Night, Kenyan Aviatrix Beryl Markham suggests the matriarchal society of elephants may be a recent adaptation, since perhaps 1930, to the arrival of firearmsSony VAIO PCG-383L battery. She describes elephant herds containing multiple adult males as well as females. She further describes how the females attempted to hide the males (hunted disproportionately for their tusks) from hunters.[64]

Mating

See also: Asian elephant#Reproduction

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2011) Sony VAIO PCG-382L battery

Elephant mating behaviour.

Elephant mating behaviour (2)

The mating season is short and females are only able to conceive for a few days each year. She will detach herself from the herd. The scent of the female (cow) elephant in heat (or estrus) attracts the male and she also uses audible signals to attract the male. As the female can usually outrun the male, she does not have to mate with every male that approaches herSony VAIO PCG-381L battery.

The male initiates the courtship and the female ignores him for several minutes. He then stops and starts again. Elephants display a range of affectionate interactions, such as nuzzling, trunk intertwining, and placing their trunks in each other's mouths (image 2).

In a rarely observed display of his affection, he may drape his trunk outside of his tusks during the ritual (image 1) Sony VAIO PCG-7185L battery. The interactions may last for 20–30 minutes and do not necessarily result in the male mounting the female, though he may demonstrate arousal during the ritual.

The female elephant is not passive in the ritual and uses the same techniques as the male.

African as well as Asiatic males will engage in same-sex bonding and mounting. The encounters are analogous to heterosexual bouts, one male often extending his trunk along the other's back and pushing forward with his tusks to signify his intention to mountSony VAIO PCG-7184L battery. Unlike heterosexual relations, which are always of a fleeting nature, those between males result in a "companionship", consisting of an older individual and one or two younger, attendant males. Same-sex relations are common and frequent in both sexes, with Asiatic elephants in captivity devoting roughly 46% of sexual encounters to same-sex activitySony VAIO PCG-7183L battery.

Intelligence

Main article: Elephant intelligence

Human, pilot whale and elephant brains up to scale. (1)-cerebrum (1a)-temporal lobe and (2)-cerebellum.

With a mass just over 5 kg (11 lb), elephant brains are larger than those of any other land animal. A wide variety of behaviours associated with intelligence have been attributed to elephants, including those associated with grief, making music, art, altruism, allomotheringSony VAIO PCG-7182L battery, play, use of tools,[66] compassion and self-awareness.[67] Elephants are believed to rank equally in terms of intelligence with cetaceans and nonhuman primates. The elephant's brain is similar to that of humans in terms of structure and complexity; the elephant brain exhibits a gyral pattern more complex and with more numerous convolutes, or brain folds, than that of humansSony VAIO PCG-7181L battery, primates or carnivores, but less complex than cetaceans.[68] However, the cortex of the elephant brain is "thicker than that of cetaceans" and is believed to have as many cortical neurons (nerve cells) and cortical synapses as that of humans, which exceeds that of cetaceans.[69]

Senses

Elephants have well innervated trunks and an exceptional sense of hearing and smell. The hearing receptors reside not only in ears, but also in trunks that are sensitive to vibrationsSony VAIO PCG-7174L battery, and most significantly feet, which have special receptors for low frequency sound and are exceptionally well innervated. Elephants communicate by sound over large distances of several kilometers partly through the ground, which is important for their social lives. Elephants have been observed listening by putting their trunks on the ground and by careful positioning their feetSony VAIO PCG-7173L battery.

The eyesight of elephants is relatively poor.

Self-awareness

Mirror self recognition is a test of self-awareness and cognition used in animal studies. A mirror was provided and visible marks were made on the elephant. The elephant investigated these marks which were visible only via the mirror. The tests also included invisible marks to rule out the possibility of their using other senses to detect these marksSony VAIO PCG-7172L battery. This shows that elephants recognize the fact that the image in the mirror is their own self, and such abilities are considered the basis for empathy, altruism and higher social interactions. This ability has also been demonstrated in humans, apes, bottlenose dolphins,[70] and magpies.[71]

A young elephant in ZimbabweSony VAIO PCG-7171L battery.

Communication

Elephants make a number of sounds when communicating. Elephants are famous for their trumpet calls, which are made when the animal blows through its nostrils. Trumpeting is usually made during excitement. Its use varies from startlement to a cry of help to rage. Elephants also make rumbling growls when greeting each otherSony VAIO PCG-7162L battery. The growl becomes a bellow when the mouth is open and a bellow becomes a moan when prolonged. This can escalate with a roar when threatening another elephant or another animal.

Elephants can communicate over long distances by producing and receiving low-frequency sound (infrasound), a sub-sonic rumbling, which can travel in the air and through the ground much farther than higher frequenciesSony VAIO PCG-7161L battery. These calls range in frequency from 15–35 Hz and can be as loud as 117 dB, allowing communication for many kilometres, with a possible maximum range of around 10 km.[72] This sound can be felt by the sensitive skin of an elephant's feet and trunk, which pick up the resonant vibrations much as the flat skin on the head of a drum. To listen attentivelySony VAIO PCG-7154L battery, every member of the herd will lift one foreleg from the ground, and face the source of the sound, or often lay its trunk on the ground. The lifting presumably increases the ground contact and sensitivity of the remaining legs. This ability is thought also to aid their navigation by use of external sources of infrasound. Discovery of this new aspect of elephant social communication and perception came with breakthroughs in audio technologySony VAIO PCG-7153L battery, which can pick up frequencies outside the range of the human ear. Pioneering research in elephant infrasound communication was done by Katy Payne, of the Elephant Listening Project,[73] and is detailed in her book Silent Thunder. Though this research is still in its infancy, it is helping to solve many mysteries, such as how elephants can find distant potential mates, and how social groups are able to coordinate their movements over extensive range. Sony VAIO PCG-7152L batteryJoyce Poole has also begun decoding elephant utterances that have been recorded over many years of observation, hoping to create a lexicon based on a systematic catalogue of elephant sounds.[74]

Diet

Elephants are herbivores and spend up to 16 hours a day eating plants. Their diets are highly variable, both seasonally and across habitats and regions. Elephants are primarily browsers, feeding on the leaves, bark and fruits of trees and shrubsSony VAIO PCG-7151L battery, but they may also eat considerable amounts of grasses and herbs. As is true for other nonruminant ungulates, elephants only digest approximately 40% of what they eat. They make up for their digestive systems' lack of efficiency in volume. An adult elephant consumes 140–270 kg (300–600 lb) of food a day
Sony VAIO PCG-7148L battery.

Sleep

Further information: Sleep (non-human)

The average sleep time of an elephant is said to be only two plus hours per day. This is thought to be because they are so big they have to eat most of the time.[76] The large size of their brains comes primarily from glial cells, which do not form action potentials, so could effect circadian rhythms. Sony VPCW21M2E/WI battery

Reproduction and life cycle

Elephant calves

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Female elephant social life revolves around breeding and raising of the calves. A female will usually be ready to breed around the age of thirteen when she comes into estrusSony VPCW21C7E battery, a short phase of receptiveness lasting a couple of days, for the first time. Females announce their estrus with smell signals and special calls.

Female African elephant with calf, in Kenya.

Females prefer bigger, stronger, and, most importantly, older males. Such a reproductive strategy tends to increase their offspring's chances of survival.

After a twenty-two-month pregnancy, the mother gives birth to a single calf that weighs about 115 kg (250 lb) and stands over 75 cm (2.5 ft) tallSony VPCW12S1E/WZ battery. Elephants have a very long development. As is common with more intelligent species, they are born with fewer survival instincts than many other animals. Instead, they rely on their elders to teach them what they need to know. Today, however, the pressures humans have put on the wild elephant populations, from poaching to habitat destructionSony VPCW12S1E/W battery, mean that the elderly often die at a younger age, leaving fewer teachers for the young. The consequences of this for the next generation are not known.

A new calf is usually the center of attention for herd members. Adults and most of the other young will gather around the newborn, touching and caressing it with their trunks. The baby is born nearly blind and at first relies almost completely on its trunk to discover the world around itSony VPCW12S1E/T battery.

Elephants within a herd are usually related and all members of the tightly knit female group participate in the care and protection of the young. After the initial excitement, the mother will usually select several full-time baby-sitters for allomothering. An elephant is considered an allomother when she is not able to have her own calfSony VPCW12S1E/P battery, usually because she is too old to breed or too young. The more allomothers, the better the calf's chances of survival. A benefit of being an allomother is that she can gain experience or receive assistance when caring for her own calf. According to Cynthia Moss, a well known researcher, these allomothers will help in all aspects of raising the calf except nursing it. Sony VPCW11S1E/W battery They walk with the young as the herd travels, helping the calves along if they fall or get stuck in the mud. The more allomothers a calf has, the more free time its mother has to feed herself. Providing a calf with nutritious milk means the mother has to eat more nutritious food herself.

Effect on the environment

Elephants do not fully digest their food. Other animals, such as this Baboon may pick through elephant dung looking for undigested seedsSony VPCW11S1E/T battery

Elephants can have profound impacts on the ecosystems they occupy with both positive and negative effects on other species, especially with their foraging activities. By pulling down trees to eat leaves, breaking branches and pulling out roots, they reduce woody cover, creating clearings in forests, converting forests to savannas and converting savannas to grasslands. These changes tend to benefit grazers at the expense of browsersSony VPCW11S1E/P battery.

Dung beetles and termites both eat elephant feces. During the dry season, elephants use their tusks to dig into river beds to reach underground sources of water. These holes may then become essential sources of water for other species. Elephants make paths through their environment that are used by other animalsSony VPCYA1S1E/B battery. Some of these pathways have apparently been used by multiple generations of elephants, used by humans and eventually even been converted to roads. A well documented example of this is the road down the Zambezi Escarpment from Makuti to Kariba in Zimbabwe.

Threats

Men with African elephant tusks, Dar es Salaam, c. 1900

Hunting

Main article: Ivory trade

The threat to the African elephant presented by the ivory trade is unique to the species. Larger, long-lived, slow-breeding animals, like the elephant, are more susceptible to overhunting than other animalsSony VPCYA1V9E/B battery. They cannot hide, and it takes many years for an elephant to grow and reproduce. An elephant needs an average of 140 kg (300 lb) of vegetation a day to survive. As large predators are hunted, the local small grazer populations (the elephant's food competitors) find themselves on the rise. The increased number of herbivores ravage the local trees, shrubs, and grassesSony VPCY21S1E/SI battery. Elephants themselves have few natural predators besides man and, occasionally, lions. However, many African governments legally allow limited hunting. The large amount of money that is charged for the necessary permits is often used to support conservation efforts, and the small number of permits issued (usually for older animals) ensure that populations are not depleted. Sony VPCY21S1E/L battery

At the turn of the 20th century, it is estimated that elephants numbered between 5 and 10 million, but hunting and habitat destruction had reduced their numbers to 400,000 to 500,000 by the end of the century.[81] In the ten years preceding 1990 the population more than halved from 1.3 million to around 600,000, largely caused by the ivory tradeSony VPCY21S1E/G battery, prompting an international ivory ban.[82][83] While elephant populations are increasing in parts of southern and eastern Africa,[84] other African nations report a decrease of their elephant populations by as much as two-thirds, and populations in even some protected areas are in danger of being eliminated[85] Chad has a decades-old history of poaching of elephantsSony VPCY11S1E/S battery, which has caused the elephant population of the region, which exceeded 300,000 in 1970, to drop to approximately 10,000 today.[86] In Virunga National Park, in eastern Democratic Republic of Congo, the number of elephants living in the observable area of the park fell from 2,889 in 1951 to 348 in 2006.[87]

Habitat loss

Another threat to elephants' survival in general is the ongoing cultivation of their habitats with increasing risk of conflicts of interest with human cohabitantsSony VPCY11S1E battery. These conflicts kill 150 elephants and up to 100 people per year in Sri Lanka.[88] The Asian elephants' demise can be attributed mostly to loss of its habitat. For African elephants, a technique was introduced successfully in 2011 that largely prevented savannah elephants from raiding farmers' croplands. Beehive fences were put around farming areas scaring the elephants away from the areas and providing the farmers with additional source of income. Sony VPCZ11X9E/B battery

As larger patches of forest disappear, the ecosystem is affected in profound ways. The trees are responsible for anchoring soil and absorbing water runoff. Floods and massive erosion are common results of deforestation. Elephants need massive tracts of land because, much like the slash-and-burn farmers, they are used to crashing through the forestSony VPCZ11Z9E/B battery, tearing down trees and shrubs for food and then cycling back later on, when the area has regrown. As forests are reduced to small pockets, elephants become part of the problem, quickly destroying all the vegetation in an area, eliminating all their resources.

National parks

Africa's first official reserve, Kruger National Park, eventually became one of the world's most famous and successful national parks.[90] There are, however, many problems associated with the establishment of these reservesSony VPCZ12M9E/B battery. For example, elephants range through a wide tract of land with little regard for national borders. Once a reserve is established and fences erected, many animals find themselves cut off from their winter feeding grounds or spring breeding areas. Some animals may die as a result, while others, like the elephants, may just trample over the fences, wreaking havoc in nearby fieldsSony VPCZ12X9E/X battery. When confined to small territories, elephants can inflict an enormous amount of damage to the local landscapes.[91]

Additionally, some reserves, such as Kruger National Park has, in the opinion of wildlife managers, suffered from elephant overcrowding, at the expense of other species of wildlife within the reserve. On 25 February 2008, the South Africa announced that they would reintroduce culling for the first time since 1994 to control elephant numbers although no cull has yet taken place. Sony VPCZ12Z9E/X battery Nevertheless, as scientists learn more about nature and the environment, it becomes very clear that these parks may be the elephants' last hope against the rapidly changing world around them.

Fertilizer

At Bengkulu province in Indonesia, four elephants died and based on the autopsy of one of them there was a high content of nitrogen in its body. The initial suspicion is the elephants had eaten fertilizer spread around trees in the plantationSony VPCZ138GA battery. The elephants may have been after the salt in the fertilizer and that would have led to their deaths.[93]

Humans and elephants

Elephant pillar carvings at Kailash Temple[disambiguation needed ], India

Hunting

Indian(?) elephant, from a Lombardy manuscript, circa 1400.

Elephant hunting, both legal and illegal, has had some unexpected consequences on elephant anatomy as well. African ivory hunters, by killing only tusked elephants, have given a much larger chance of mating to elephants with small tusks or no tusks at allSony VPCZ13M9E/B battery. The propagation of the absent-tusk gene has resulted in the birth of large numbers of tuskless elephants, now approaching 30% in some populations (compare with a rate of about 1% in 1930)[citation needed]. Tusklessness, once a rare genetic abnormality, has become a widespread hereditary traitSony VPCZ13M9E/X battery.

It is possible, if unlikely, that continued selection pressure could bring about a complete absence of tusks in African elephants. The effect of tuskless elephants on the environment, and on the elephants themselves, could be dramatic. Elephants use their tusks to root around in the ground for necessary minerals, tear apart vegetation, and spar with one another for mating rights. Without tusks, elephant behaviour could change dramatically. Sony VPCZ13V9E battery

Domestication and use

Elephants are used to entertain tourists at some beaches as at Havelock Island, India.

Elephants have been working animals used in various capacities by humans. Seals found in the Indus Valley suggest that the elephant was first domesticated in ancient India. However, elephants have never been truly domesticated: the male elephant in his periodic condition of musth is dangerous and difficult to controlSony VPCZ13V9E/X battery. Therefore, elephants used by humans have typically been female, war elephants being an exception; as female elephants in battle will run from a male, only males could be used in war. It is generally more economical to capture wild young elephants and tame them than to breed them in captivity (see also elephant "crushing")Sony VPCZ13Z9E/X battery.

The Judean rebel Eleazar Maccabeus kills a Seleucid war elephant and is crushed under it (Miniature from a manuscript Speculum Humanae Salvationis).

The Laotians have been domesticating elephants for centuries, and about 500 domesticated elephants are still employed, the majority of which work in the Xaignabouli province. These elephants are mainly employed in the logging industrySony VPCZ21M9E battery, with ecotourism emerging as a sustainable and environmentally friendly alternative. Elefantasia is a local INGO aiming to reconvert logging elephants into ecotourism practices, thus allowing Asian elephants the ability to supply their mahouts with income while still allowing them to breed.

Elephants are also commonly exhibited in zoos and wild animal parksSony VPCZ21Q9E battery. About 1200 elephants are kept in western zoos. A study shows that the lifespan of elephants in European zoos is about half as long as those living in protected areas in Africa and Asia.[95] As of July 2010, the oldest living African elephant in captivity is Ruaha (59) at Zoo Basel .

Elephants are revered in India (and are worshipped in ceremonies such as the Aanayoottu) Sony VPCZ21V9E battery.

Warfare

Main article: War elephant

War elephants were used by armies in the Indian subcontinent, the Warring States of China and later by the Persian Empire. This use was adopted by Hellenistic armies after Alexander the Great experienced their value against King Porus, notably in the Ptolemaic and Seleucid diadoch empires. The Carthaginian general Hannibal took elephants across the Alps when he was fighting the RomansSony VPCEH3T9E battery, but brought too few elephants to be of much military use, although his horse cavalry was quite successful. He probably used a now-extinct third African subspecies, the North African forest elephant, smaller than its two southern cousins and presumably easier to domesticate. A large elephant in full charge could cause tremendous damage to infantry and cavalry horses would be afraid of them (see Battle of Hydaspes) Sony VPCEH3N6E battery.

In the Southeast Asia, the powerful Khmer Empire had come to regional dominance by the 9th century AD, drawing heavily on the use of war elephants. With the collapse of Khmer power in the 15th century, the successor region powers of Burma (now Myanmar) and Siam (now Thailand) also adopted the widespread use of war elephants. A notable example of a battle using elephants in Southeast Asia is YuttahadhiSony VPCEH3N1E battery.

Elephants in use by Indian cavalry

Embroidered housings and trappings of the elephant and Howdah exhibited by her Majesty in Great Exhibition

Industry

Elephant work camp in Thailand. Elephants are used for heavy forest work and in circus presentations.

Throughout Burma, Siam, India, and most of South Asia, elephants were used in the military for heavy labour, especially for uprooting trees and moving logs, and were also commonly used as executioners to crush the condemned underfootSony VPCEH3D0E battery.

Elephants have also been used as mounts for safari-type hunting, especially Indian shikar (mainly on tigers), and as ceremonial mounts for royal and religious occasions, while Asian elephants have been used for transport and entertainment.

Zoo and circuses

There is growing resistance[97] against the capture, confinement and use of wild elephants. Animal rights advocates allege elephants in zoos and circuses "suffer a life of chronic physical ailments, social deprivation, emotional starvation and premature death".Sony VPCEH3B1E battery Zoos argue that standards for treatment of elephants are extremely high and minimum requirements for space, enclosure design, nutrition, reproduction, enrichment and veterinary care are set to ensure the well-being of elephants in captivity. However, elephants in zoos have a reduced life-span and reproduction compared to working elephants in timber camps[99] and in a survey of elephants in the UKSony VPCEH2Z1E battery, 54% of the elephants showed stereotypical behaviour. Circuses continue to have a mixed record. Recently, the city of Los Angeles closed an elephant act with Circus Vazquez due to numerous instances of abuse and neglect (April 2008),[102] and according to PETA, 27 elephants owned by Ringling Bros. and Barnum & Bailey Circus have died since 1992. Sony VPCEH2S9E battery

Elephants have traditionally been a major part of circuses around the world, being intelligent enough to be trained in a variety of acts (see for example P.T. Barnum's Jumbo and John L. Sullivan, the famous "Boxing Elephant"). However, conditions for circus elephants are unnatural (confinement in small pens or cages, restraints on their feetSony VPCEH2Q1E battery, lack of companionship of other elephants). Perhaps as a result, there are occasional instances of them attacking their keepers or handlers (examples include Black Diamond and "Murderous Mary").

Elephants raised in captivity sometimes show "rocking behavior", a rhythmic and repetitive swaying which is unreported in free-ranging wild elephants. Thought to be symptomatic of stress disorders, and probably made worse by a barren environment, Sony VPCEH2P0E battery rocking behavior may be a precursor to aggressive behavior in captive elephants. This link is to an image of Devi (little princess), a 30-year-old Asian elephant raised in captivity at the San Diego Zoo showing "rocking behavior".

Hybrids

African and Asian elephant species have disjunct distributions, and do not hybridize in the wild. However, in 1978 at Chester Zoo, an Asian elephant cow gave birth to a hybrid calf sired by an African elephant bullSony VPCEH2N1E battery. "Motty", the resulting hybrid male calf, had an African elephant's cheeks, ears (large with pointed lobes) and legs (longer and slimmer), but the toenail numbers (five for each front foot, four hind), and the single trunk finger of an Asian elephant. His wrinkled trunk was like that of an African elephant. His forehead was sloping with one dome and two smaller domes behind itSony VPCEH2M9E battery. The body was African in type, but had an Asian-type center hump and an African-type rear hump. The calf died of infection 12 days later.[107] It is preserved as a mounted specimen at the British Natural History Museum, London. There are unconfirmed rumors of three other hybrid elephants born in zoos or circuses; all are said to have been deformed and none survivedSony VPCEH2M1E battery.

Elephant aggression

Devi (little princess), a 30-year-old Asian elephant raised in captivity at the San Diego Zoo exhibiting "rocking behavior" (animation), a rhythmic and repetitive swaying which is unreported in free ranging wild elephants. Thought to be symptomatic of stress disorders, and probably made worse by a barren environment,[104] rocking behavior may be a precursor to aggressive behavior in captive elephantsSony VPCEH2L9E battery.

Elephants can crush and kill any other land animal, even the rhinoceros. They can experience bouts of rage and engage in actions that have been interpreted as vindictive.[108] In Africa, groups of young teenage elephants attacked human villages after cullings done in the 1970s and 80s. In India, male elephants regularly attack villages at night, destroying homes and killing peopleSony VPCEH2J1E battery. In the Indian state of Jharkhand, 300 people were killed by elephants between 2000 and 2004, and in Assam, 239 people were reported killed by elephants between 2001 and 2006.[108]

Musth

Main article: Musth

Adult male elephants periodically enter the state called musth (Hindi for "madness"), sometimes spelled "must" in English. Elephants in musth display highly aggressive behavior and elevated levels of reproductive hormonesSony VPCEH2H1E battery.

Other causes

Local people have reported their belief that some elephants were drunk during their attacks, although there is no confirmed evidence of this. In December 1998, a herd of elephants overran a village in India. Although locals reported that nearby elephants had recently been observed drinking beer which rendered them "unpredictable"Sony VPCEH2F1E battery, officials considered it the least likely explanation for the attack. An attack on another Indian village occurred in October 1999, and again locals believed the reason was drunkenness, but again the theory was not widely accepted.[112] Purportedly drunk elephants raided yet another Indian village again on December 2002, killing six people, which led to the killing of about 200 elephants by localsSony VPCEH2E0E battery.

In popular culture

See also: Cultural depictions of elephants

Elephants are ubiquitous in Western popular culture as emblems of the exotic[114] because their unique appearance and size sets them apart from other animals and because, like other African animals such as the giraffe, rhinoceros, and hippopotamus, they are unfamiliar to Western audiences. Popular culture's stock references to elephants rely on this exotic uniquenessSony VPCEH2D0E battery. For instance, a "white elephant" is a byword for something expensive, useless and bizarre.

As characters, elephants are relegated largely to children's literature,[114] in which they are generally cast as models of exemplary behaviour,[114] but account for some of this branch of literature's most iconic characters. Many stories tell of isolated young elephants returning to a close-knit communitySony VPCEH2C0E battery, such as The Elephant’s Child from Rudyard Kipling's Just So Stories (1902), Dumbo (1942) or The Saggy Baggy Elephant (1947). Other elephant heroes given human qualities include Laurent de Brunhoff's anthropomorphic Babar (1935), David McKee's Elmer (1989) and Dr. Seuss's Horton (1940). More than other exotic animals, elephants in fiction are surrogates for humansSony VPCEH1Z1E battery, with their concern for the community and each other depicted as something to aspire to.[116]

The use of the elephant as a symbol of the Republican Party (United States) began with an 1874 cartoon by Thomas Nast.

The University of Alabama has a mascot of an elephant named Big Al.

A crocodile is any species belonging to the family Crocodylidae (sometimes classified instead as the subfamily Crocodylinae). The term can also be used more loosely to include all extant members of the order Crocodilia: i.e. the true crocodiles, the alligators and caimans (family Alligatoridae) and the gharials (family Gavialidae) (AKKU Sony VGP-BPS13), as well as the Crocodylomorpha, which include prehistoric crocodile relatives and ancestors.

Member species of the family Crocodylidae are large aquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. Crocodiles tend to congregate in freshwater habitats such as rivers, lakes, wetlands and sometimes in brackish water. They feed mostly on vertebrates -(AKKU Sony VGP-BPS13A/B) fish, reptiles, and mammals, and sometimes on invertebrates - molluscs and crustaceans, depending on species. They first appeared during the Eocene epoch, about 55 million years ago.

Etymology

The word "crocodile" comes from the Ancient Greek κροκόδιλος (crocodilos), "lizard," used in the phrase ho krokódilos ho potamós, "the lizard of the (Nile) river".

There are several variant Greek forms of the word attested, including the later form κροκόδειλος (crocodeilos)[2] found cited in many English reference works(AKKU Sony VGP-BPS13B/B).[3] In the Koine Greek of Roman times, crocodilos and crocodeilos would have been pronounced identically, and either or both may be the source of the Latinized form crocodīlus used by the ancient Romans.

Crocodilos or crocodeilos is a compound of krokè ("pebbles"), and drilos/dreilos ("worm"). It is ascribed to Herodotus, supposedly to describe the basking habits of the Egyptian crocodile. (AKKU Sony VGP-BPS13/S) However the word drilos is only attested as a colloquial term for "penis".[5] The meaning of krokè is explained as describing the skin texture of lizards (or crocodiles) in most sources,[citation needed] but is alternately claimed to refer to a supposed habit of (lizards or crocodiles) basking on pebbly ground.

The form crocodrillus is attested in Medieval Latin(AKKU Sony VGP-BPS13B/S).[4] It is not clear whether this is a medieval corruption or derives from alternate Greco-Latin forms (late Greek corcodrillos and corcodrillion are attested).

A (further) corrupted form cocodrille is found in Old French and was borrowed into Middle English as cocodril(le). The Modern English form crocodile was adapted directly from the Classical Latin crocodīlus in the 16th century, replacing the earlier form.

The use of -y- in the scientific name Crocodylus (and forms derived from it) is a corruption introduced by Laurenti (1768) (AKKU Sony VGP-BPS13A/S).

Description

Crocodiles are similar to alligators and caimans; for their common biology and differences between them, see Crocodilia.

Crocodiles, like dinosaurs, have the abdominal ribs modified into gastralia.

Crocodiles are among the more biologically complex reptiles despite their prehistoric look. Unlike other reptiles, a crocodile has a cerebral cortex, a four-chambered heart,and the functional equivalent of a diaphragm, by incorporating muscles used for aquatic locomotion into respiration (e.g. m. diaphragmaticus); (AKKU Sony VGP-BPS13A/Q) Its external morphology, on the other hand, is a sign of its aquatic and predatory lifestyle.

A crocodile’s physical traits allow it to be a successful predator. Its streamlined body enables it to swim swiftly. It also tucks its feet to the side while swimming, which makes it faster by decreasing water resistance. Its webbed feet, though not used to propel the animal through the water, allow it to make fast turns and sudden moves in the water or initiate swimming(AKKU Sony VGP-BPS13B/Q). Webbed feet are an advantage in shallower water where the animal sometimes moves around by walking.

Crocodiles have a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water. The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence. Like other archosaurs, crocodilians are diapsid, although their post-temporal fenestrae are reduced(AKKU Sony VGP-BPS13Q). The walls of the braincase are bony, but lack supratemporal and postfrontal bones.[7] Their tongues are not free, but held in place by a membrane which limits movement; as a result, crocodiles are unable to stick out their tongues.[8]

Crocodilian scales have pores believed to be sensory in function, analogous to the lateral line in fishes. They are particularly seen on their upper and lower jaws. Another possibility is they are secretory, as they produce an oily substance that appears to flush mud off. (Sony VGP-BPL8 Battery)

Crocodiles are very fast over short distances, even out of water. Since they feed by grabbing and holding onto their prey, they have evolved sharp teeth for tearing and holding onto flesh, and powerful muscles to close the jaws and hold them shut. These jaws can bite down with immense force, by far the strongest bite of any animal(Sony VGP-BPL8A Battery). The pressure of the crocodile's bite is more than 5,000 pounds per square inch (30,000 kPa),[9] compared to just 335 pounds per square inch (2,300 kPa) for a Rottweiler, 400 pounds per square inch (2,800 kPa) for a large great white shark, 800 pounds per square inch (6,000 kPa) to 1,000 pounds per square inch (7,000 kPa) for a hyena, or 2,000 pounds per square inch (10,000 kPa) for a large alligator(Sony VGN-FZ130E/B Battery). The jaws are opened, however, by a very weak set of muscles. Crocodiles can thus be subdued for study or transport by taping their jaws or holding their jaws shut with large rubber bands cut from automobile inner tubes. They have limited lateral (side-to-side) neck movement.

Biology and behavior

Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they have a very slow metabolism(Sony VGN-FZ130E/BA Battery), so they can survive long periods without food. Despite their appearance of being slow, crocodiles are top predators in their environment, and various species have been observed attacking and killing sharks.[10]

Herodotus claimed Nile crocodiles had a symbiotic relationship with certain birds, such as the Egyptian plover, which enter the crocodile's mouth and pick leeches feeding on the crocodile's blood; with no evidence of this interaction actually occurring in any crocodile species, it is most likely mythical or allegorical fiction(Sony VGN-FZ130E/BB Battery).[11]

Many large crocodilians swallow stones (called gastroliths or stomach stones) which may act as ballast to balance their bodies or assist in crushing food,[7] similar to grit in birds.

Salt glands are present in the tongues of most crocodylids and they have a pore opening on the surface of the tongue. They appear to be similar to those in marine turtles; they seem to be absent in Alligatoridae. (Sony VGP-BPL9 Akku)

Crocodilians can produce sounds during distress and in aggressive displays. They can also hear well, but their tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.[7]

A crocodile farm in Mexico

Crocodiles eat fish, birds, mammals and occasionally smaller crocodiles.

Crocodiles are protected in many parts of the world, but they also are farmed commercially. Their hides are tanned and used to make leather goods such as shoes and handbags; crocodile meat is also considered a delicacy(Sony VGP-BPL9/B Akku). The most commonly farmed species are the saltwater and Nile crocodiles, while a hybrid of the saltwater and the rare Siamese crocodile is also bred in Asian farms. Farming has resulted in an increase in the saltwater crocodile population in Australia, as eggs are usually harvested from the wild, so landowners have an incentive to conserve their habitat(Sony VGP-BPL9/S Akku).

Distribution of crocodiles

Crocodiles are more closely related to birds and dinosaurs than to most animals classified as reptiles, the three being included in the group Archosauria ('ruling reptiles'). See Crocodilia for more information.

Crocodile embryos do not have sex chromosomes, and unlike humans, sex is not determined genetically. Sex is determined by temperature, with males produced at around 31.6 °C (89 °F), and females produced at slightly lower and higher temperatures(Sony VGP-BPL9A/B Akku). The average incubation period is around 80 days, and also is dependent on temperature.[12]

Crocodiles may possess a form of homing instinct. Three rogue saltwater crocodiles were relocated 400 kilometres by helicopter in northern Australia, but had returned to their original locations within three weeks, based on data obtained from tracking devices attached to the reptiles. (Sony VGP-BPL9A Akku)

The land speed record for a crocodile is 17 km/h (11 mph) measured in a galloping Australian freshwater crocodile.[14] Maximum speed varies from species to species. Certain species can indeed gallop, including Cuban crocodiles, New Guinea crocodiles, African dwarf crocodiles, and even small Nile crocodiles(Sony VGP-BPL9 Akku). The fastest means by which most species can move is a kind of "belly run", where the body moves in a snake-like fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of 10 or 11 km/h (around 7 mph) when they "belly run", and often faster if slipping down muddy riverbanks. Another form of locomotion is the "high walk", where the body is raised clear of the ground(Sony VGP-BPS21 Akku).

Siamese crocodile sleeping with its mouth open to pant

Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may even pant like a dog.[15]

The BBC TV[16] reported thee Nile crocodile which has lurked a long time underwater to catch prey, has built up a large oxygen debt. When it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide from its muscles directly to its stomach(Sony VGP-BPS21A Akku); the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone.

Size

A large saltwater crocodile in captivity in Australia

Size greatly varies between species, from the dwarf crocodile to the saltwater crocodile. Species of Palaeosuchus and Osteolaemus grow to an adult size of just 1 metre (3.3 ft) to 1.5 metres (4.9 ft). Larger species can reach over 4.85 metres (15.9 ft) long and weigh well over 1,200 kilograms (2,600 lb). Crocodilians show pronounced sexual dimorphism(Sony VGP-BPS21B Akku), with males growing much larger and more rapidly than females.[7] Despite their large adult sizes, crocodiles start their lives at around 20 centimetres (7.9 in) long. The largest species of crocodile is the saltwater crocodile, found in eastern India, northern Australia, throughout South-east Asia, and in the surrounding waters(Sony VGP-BPS21A/B Akku).

Two larger certifiable records are both of 6.2 metres (20 ft) crocodiles. The first was shot in the Mary River in the Northern Territory of Australia in 1974 by poachers, and measured by wildlife rangers.[citation needed] The second crocodile was killed in 1983 in the Fly River, Papua New Guinea. In the case of the second crocodile it was actually the skin that was measured by zoologist Jerome Montague(Sony VGP-BPS21/S Akku), and as skins are known to underestimate the size of the actual animal, it is possible this crocodile was at least another 10 cm longer.[citation needed]

The largest crocodile ever held in captivity is an estuarine–Siamese hybrid named Yai (Thai: ใหญ่, meaning big) (born 10 June 1972) at the famous Samutprakarn Crocodile Farm and Zoo, Thailand. This animal measures 6 m (19.69 ft) (19 ft 8 in) in length and weighs 1114.27 kg(Akku Sony VGP-BPL14).[17]

Meanwhile, the longest crocodile captured alive is Lolong which was measured at 6.096 metres (20 ft 3 in) by a National Geographic team in Agusan del Sur Province, Philippines.[18]

Wildlife experts, however, argue the largest crocodile so far found in the Bhitarkanika was almost 23 feet (7.0 m) long, which could be traced from the skull preserved by the Kanika royal family( Akku Sony VGP-BPL14 ). The crocodile was shot near Dhamara in 1926 and later its skull was preserved by the then Kanika king. Crocodile experts estimated the animal was between 20 feet (6.1 m) and 23 feet (7.0 m) long, as the size of the skull was measured one-ninth of the total length of the body.[citation needed]

Age

Measuring crocodile age is unreliable, although several techniques are used to derive a reasonable guess(Akku Sony VGP-BPS14/S ). The most common method is to measure lamellar growth rings in bones and teeth—each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons.[19] Bearing these inaccuracies in mind, the oldest crocodilians appear to be the largest species. C. porosus is estimated to live around 70 years on average(Akku Sony VGP-BPL14/B), with limited evidence of some individuals exceeding 100 years. One of the oldest crocodiles recorded died in a zoo in Russia. A male freshwater crocodile at the Australia Zoo is estimated to be 130 years old. He was rescued from the wild by Bob Irwin and Steve Irwin after being shot twice by hunters. As a result of the shootings, this crocodile (known affectionately as "Mr. Freshy") has lost his right eye(Akku Sony VGP-BPS14/B ).

Skin

Crocodiles have smooth skin on their bellies and sides, while their dorsal surfaces are armoured with large osteoderms. The armoured skin has scales and is thick and rugged, providing some protection. They are still able to absorb heat through this armour, as a network of small capillaries allow blood through the scales to absorb heat(AKKU sony VAIO VGN-FW21E).

Taxonomy of the Crocodylidae

Phylogeny

The cladogram below follows the topology from a 2012 analysis of morphological traits by Christopher A. Brochu and Glenn W. Storrs. Many extinct species of Crocodylus might represent different genera. C. suchus was not included, because its morphological codings were identical to these of C. niloticus. However, the authors suggested that it could be explained by their specimen sampling, and considered the two species to be distinct(AKKU Sony VAIO VGN-FW21I).

Crocodiles and humans

Danger to humans

Main article: Crocodile attacks

Crocodile warning sign, Trinity Beach, Queensland, Australia

The larger species of crocodiles are very dangerous to humans, mainly not from their ability to run after a person, but their ability to strike before the person can react. The saltwater crocodile and Nile crocodile are the most dangerous, killing hundreds of people each year in parts of Southeast Asia and Africa. The mugger crocodile, American crocodile, American alligator and black caiman are also dangerous to humans(AKKU Sony VAIO VGN-FW21L).

Crocodile products

Main article: Crocodile farm

Crocodile leather wallets from a Bangkok crocodile farm

Chiang Mai crocodile leather belt

Crocodile leather can be made into goods such as wallets, briefcases, purses, handbags, belts, hats, and shoes.

Crocodile meat is consumed in some countries, such as Australia, Ethiopia, Thailand, South Africa and also Cuba (in pickled form); it can also be found in specialty restaurants in some parts of the United States(AKKU Sony VAIO VGN-FW21Z). The meat is white and its nutritional composition compares favourably with that of other meats.[citation needed] It tends to have a slightly higher cholesterol level than other meats.[citation needed] Crocodile meat has a delicate flavour; some describe it as a cross between chicken and crab.[citation needed] Cuts of meat include backstrap and tail fillet(AKKU Sony VAIO VGN-FW21M).

The panda (Ailuropoda melanoleuca, lit. "black and white cat-foot"),[2] also known as the giant panda to distinguish it from the unrelated red panda, is a bear[3] native to central-western and south western China.[4] It is easily recognized by its large, distinctive black patches around the eyes, over the ears, and across its round body. Though it belongs to the order Carnivora(AKKU Sony VAIO VGN-FW31M), the panda's diet is 99% bamboo.[5] Pandas in the wild will occasionally eat other grasses, wild tubers, or even meat in the form of birds, rodents or carrion. In captivity they may receive honey, eggs, fish, yams, shrub leaves, oranges, or bananas along with specially prepared food.

The giant panda lives in a few mountain ranges in central China, mainly in Sichuan province, but also in the Shaanxi and Gansu provinces.[8] As a result of farming, deforestation and other development, the panda has been driven out of the lowland areas where it once lived(AKKU Sony VAIO VGN-FW31J).

The panda is a conservation reliant endangered species.[4] A 2007 report shows 239 pandas living in captivity inside China and another 27 outside the country. Wild population estimates vary; one estimate shows that there are about 1,590 individuals living in the wild,[9] while a 2006 study via DNA analysis estimated that this figure could be as high as 2,000 to 3,000. (AKKU Sony VAIO VGN-FW31E) Some reports also show that the number of pandas in the wild is on the rise. However, the IUCN does not believe there is enough certainty yet to reclassify the species from Endangered to Vulnerable.[1]

While the dragon has often served as China's national emblem, internationally the panda appears at least as commonly. As such, it is becoming widely used within China in international contexts, for example the five Fuwa mascots of the Beijing Olympics(AKKU Sony VAIO VGN-FW31Z).

Description

Skull, as illustrated in Pocock's The Fauna of British India, including Ceylon and Burma – Mammalia Vol 2

A giant panda cub. At birth, the giant panda typically weighs 100 to 200 grams (3 1⁄2 to 7 oz) and measures 15 to 17 centimeters (6 to 7 in) long.[13]

The giant panda has a black-and-white coat. Adults measure around 1.2 to 1.8 meters (4 to 6 ft) long, including a tail of about 13 cm (5.1 in), and 60 to 90 centimeters (1 ft 10 in to 2 ft 10 in) tall at the shoulder. (AKKU Sony VAIO VGN-FW31ZJ) Males can weigh up to 160 kilograms (350 lb).[15] Females (generally 10–20% smaller than males)[16] can weigh as little as 75 kg (170 lb) but can also weigh up to 125 kilograms (280 lb). Average adult weight is 100 to 115 kilograms (220 to 250 lb).

The giant panda has a body shape typical of bears. It has black fur on its ears, eye patches, muzzle, legs, arms and shoulders. The rest of the animal's coat is white. Although scientists do not know why these unusual bears are black and white, some speculate that the bold (AKKU Sony VAIO VGN-FW32Z)coloring provides effective camouflage in its shade-dappled snowy and rocky surroundings.[19] The giant panda's thick, wooly coat keeps it warm in the cool forests of its habitat.[19] The giant panda has large molar teeth and strong jaw muscles for crushing tough bamboo.[20]

The giant panda's paw has a "thumb" and five fingers; the "thumb" is actually a modified sesamoid bone, which helps the giant panda to hold bamboo while eating.[21] Stephen Jay Gould discusses this feature in his book of essays on evolution and biology, The Panda's Thumb(AKKU Sony VAIO PCG-5G2L).

The giant panda's tail, measuring 10 to 15 centimeters (4 to 6 in), is the second longest in the bear family. The longest belongs to the Sloth Bear.[16]

The giant panda typically lives around 20 years in the wild and up to 30 years in captivity.[22] The recorded age of the oldest captive giant panda, a female named Ming Ming, is 34.[23]

Behavior

In the wild, the giant panda is a terrestrial animal and primarily spends its life roaming and feeding in the bamboo forests of the Qinling Mountains and in the hilly Sichuan Province. (AKKU Sony VAIO PCG-5G3L ) Giant pandas are generally solitary,[25] and each adult has a defined territory and females are not tolerant of other females in their range. Pandas communicate through vocalization and scent marking such as clawing trees or spraying urine.[4] The giant panda is able to climb and take shelter in hollow trees or rock crevices but does not establish permanent dens. For this reason(Sony VAIO PCG-5J1L Akku), pandas do not hibernate, which is similar to other subtropical mammals, and will instead move to elevations with warmer temperatures.[26] Pandas rely primarily on spatial memory rather than visual memory.[27]

Social encounters occur primarily during the brief breeding season in which pandas in proximity to one another will gather.[28] After mating, the male leaves the female alone to raise the cub. (Sony VAIO PCG-5J2L Akku)

Though the panda is often assumed to be docile, it has been known to attack humans, presumably out of irritation rather than predation.

Feeding

Forefeet

Pandas eating bamboo at the National Zoo in Washington, D.C.

Panda eating, standing, playing

Despite its taxonomic classification as a carnivoran, the giant panda's diet is primarily herbivorous, consisting almost exclusively of bamboo.[22] However, the giant panda still has the digestive system of a carnivore, as well as carnivore-specific genes,[33] and thus derives little energy and little protein from consumption of bamboo(Sony VAIO PCG-5K2L Akku). Its ability to digest cellulose is ascribed to the microbes in its gut.[34][35] The giant panda is a "highly specialized" animal with "unique adaptations", and has lived in bamboo forests for millions of years.[25] The average giant panda eats as much as 9 to 14 kg (20 to 30 pounds) of bamboo shoots a day. Because the giant panda consumes a diet low in nutrition(Sony VAIO PCG-5K1L Akku), it is important for it to keep its digestive tract full.[22] The limited energy input imposed on it by its diet has affected the panda's behavior. The giant panda tends to limit its social interactions and avoids steeply sloping terrain in order to limit its energy expenditures.[36]

Two of the panda's most distinctive features, its large size and its round face, are adaptations to its bamboo diet. Panda researcher Russell Ciochon observed that(Sony VAIO PCG-6S1L Akku): “[much] like the vegetarian gorilla, the low body surface area to body volume [of the giant panda] is indicative of a lower metabolic rate. This lower metabolic rate and a more sedentary lifestyle allow the giant panda to subsist on nutrient poor resources such as bamboo.”[36] Similarly, the giant panda's round face is the result of powerful jaw muscles, which attach from the top of the head to the jaw.[36] Large molars crush and grind fibrous plant material(Sony VAIO PCG-6S2L Akku).

Pandas eat any of twenty-five bamboo species in the wild, such as Fargesia dracocephala[37] and Fargesia rufa.[38] Only a few bamboo species are widespread at the high altitudes pandas now inhabit. Bamboo leaves contain the highest protein levels; stems have less.[39] Given this large diet, the giant panda can defecate up to 40 times a day. (Sony VAIO PCG-6W1L Akku)

Because of the synchronous flowering, death, and regeneration of all bamboo within a species, the giant panda must have at least two different species available in its range to avoid starvation. While primarily herbivorous, the giant panda still retains decidedly ursine teeth, and will eat meat, fish, and eggs when available(Sony VAIO PCG-6W2L Akku). In captivity, zoos typically maintain the giant panda's bamboo diet, though some will provide specially formulated biscuits or other dietary supplements.[41]

Genomics

The giant panda genome was sequenced in 2009 using a next-generation sequencing technology.[42] Its genome contains 20 pairs of autosomes and one pair of sex chromosomes.

Classification

For many decades the precise taxonomic classification of the giant panda was under debate because it shares characteristics[clarification needed] of both bears and raccoons(Sony VAIO PCG-6W3L Akku).[43] However, molecular studies suggest that the giant panda is a true bear and part of the Ursidae family,[44][45] though it differentiated early in history from the main ursine stock. The giant panda's closest extant relative is the spectacled bear of South America.[46] The giant panda has been referred to as a living fossil(Sony VAIO PCG-7111L Akku).[47]

Despite the shared name, habitat type, and diet, as well as a unique enlarged bone called the pseudo thumb (which helps them grip the bamboo shoots they eat), the giant panda and red panda are only distantly related. Molecular studies have placed the red panda in its own family Ailuridae, and not under Ursidae(Sony VAIO PCG-7112L Akku).

Hua Mei, the baby panda born at the San Diego Zoo in 1999.

Subspecies

Two subspecies of giant panda have been recognized on the basis of distinct cranial measurements, color patterns, and population genetics (Wan et al., 2005).

The nominate subspecies Ailuropoda melanoleuca melanoleuca consists of most extant populations of panda. These animals are principally found in Sichuan and display the typical stark black and white contrasting colors(Sony VAIO PCG-7113L Akku).

The Qinling Panda, Ailuropoda melanoleuca qinlingensis[48] is restricted to the Qinling Mountains in Shaanxi at elevations of 1300–3000 m. The typical black and white pattern of Sichuan giant pandas is replaced with a dark brown versus light brown pattern. The skull of A. m. qinlingensis is smaller than its relatives, and it has larger molars(Sony VAIO PCG-7131L Akku).

Uses and human interaction

Early references

In the past, pandas were thought to be rare and noble creatures – the mother of Emperor Wen of Han was buried with a panda skull in her vault. The grandson of Emperor Taizong of Tang is said to have given Japan two pandas and a sheet of panda skin as a sign of goodwill. Unlike many other animals in Ancient China, pandas were rarely thought to have medical uses(Sony VAIO PCG-7132L Akku). The few known uses include the Sichuan tribal peoples' use of panda urine to melt accidentally swallowed needles, and the use of panda pelts to control menses as described in the Qin Dynasty encyclopedia Erya.[49]

The creature named mo (貘) mentioned in some ancient books has been interpreted as giant panda.[49] The dictionary Shuowen Jiezi (Eastern Han Dynasty) says that the mo, from Shu (Sichuan), is bear-like, but yellow-and-black(Sony VAIO PCG-7133L Akku),[50] although the older Erya describes mo simply as a "white leopard".[51] The interpretation of the legendary fierce creature pixiu (貔貅) as referring to the giant panda is also common.[52]

During the reign of the Yongle Emperor (early 15th century), his relative from Kaifeng sent him a captured zouyu (騶虞), and another zouyu was sighted in Shandong. Zouyu is a legendary "righteous" animal, which, similarly to a qilin(Sony VAIO PCG-7z1L Akku), only appears during the rule of a benevolent and sincere monarch. It is said to be fierce as a tiger, but gentle and strictly vegetarian, and described in some books as a white tiger with black spots. Puzzled about the real zoological identity of the creature captured during the Yongle era, J.J.L. Duyvendak exclaims, "Can it possibly have been a Pandah?" (Sony VAIO PCG-7z1L Akku)

The comparative obscurity of the giant panda throughout most of China's history is illustrated by the fact that, despite there being a number of depictions of bears in Chinese art starting from its most ancient times, and the bamboo being one of the favorite subjects for Chinese painters, there are no known pre-20th-century artistic representations of giant pandas. (Sony VAIO PCG-8Y1L Akku)

Western discovery

The West first learned of the giant panda in 1869 because the French missionary Armand David[43] received a skin from a hunter on 11 March 1869. The first Westerner known to have seen a living giant panda is the German zoologist Hugo Weigold, who purchased a cub in 1916. Kermit and Theodore Roosevelt, Jr., became the first Westerners to shoot a panda(Sony VAIO PCG-8Y2L Akku), on an expedition funded by the Field Museum of Natural History in the 1920s. In 1936, Ruth Harkness became the first Westerner to bring back a live giant panda, a cub named Su Lin[55] who went to live at the Brookfield Zoo in Chicago. In 1938, five giant pandas were sent to London;[56][57] these activities were later halted because of wars and for the next half of the century, the West knew little of pandas(Sony VAIO PCG-8Z1L Akku).

Gao Gao, an adult male giant panda at San Diego Zoo.

Panda diplomacy

Main article: Panda diplomacy

Loans of giant pandas to American and Japanese zoos formed an important part of the diplomacy of the People's Republic of China (PRC) in the 1970s, as it marked some of the first cultural exchanges between the People's Republic and the West. This practice has been termed "Panda diplomacy"(Sony VAIO PCG-8Z2L Akku).

By 1984, however, pandas were no longer given as gifts. Instead, the PRC began to offer pandas to other nations only on 10-year loans, under terms including a fee of up to US$1,000,000 per year and a provision that any cubs born during the loan are the property of the PRC. Since 1998, because of a WWF lawsuit(Akku Sony VGN-NR11M/S), the United States Fish and Wildlife Service only allows a U.S. zoo to import a panda if the zoo can ensure that the PRC will channel more than half of its loan fee into conservation efforts for the giant panda and its habitat.

In May 2005, the People's Republic of China offered a breeding pair to Taiwan. The issue became embroiled in cross-Strait relations—both over the underlying symbolism(Akku Sony VGN-NR11S/S), and over technical issues such as whether the transfer would be considered "domestic" or "international," or whether any true conservation purpose would be served by the exchange.[58] A contest in 2006 to name the pandas was held in the mainland, resulting in the politically charged names Tuan Tuan and Yuan Yuan (from tuanyuan, meaning "reunion", i.e. "reunification")(Akku Sony VGN-NR11Z/S). PRC's offer was initially rejected by President Chen of Taiwan. However when Ma Ying-jeou assumed the presidency in 2008 the offer was accepted, and the pandas arrived in December of that year.[59]

Conservation

The giant panda is an endangered species, threatened by continued habitat loss and by a very low birthrate, both in the wild and in captivity.[22]

The giant panda has been a target for poaching by locals since ancient times and by foreigners since it was introduced to the West(Akku Sony VGN-NR11Z/T). Starting in the 1930s, foreigners were unable to poach giant pandas in China because of the Second Sino-Japanese War and the Chinese Civil War, but pandas remained a source of soft furs for the locals. The population boom in China after 1949 created stress on the pandas' habitat, and the subsequent famines led to the increased hunting of wildlife, including pandas(Sony VAIO VGN-FZ11E Battery). During the Cultural Revolution, all studies and conservation activities on the pandas were stopped. After the Chinese economic reform, demand for panda skins from Hong Kong and Japan led to illegal poaching for the black market, acts generally ignored by the local officials at the time.

Close up of a baby seven-month-old panda cub in the Wolong Nature Reserve in Sichuan, China(Akku Sony VAIO VGN-FZ11L).

Though the Wolong National Nature Reserve was set up by the PRC government in 1958 to save the declining panda population, few advances in the conservation of pandas were made, owing to inexperience and insufficient knowledge of ecology. Many believed that the best way to save the pandas was to cage them. As a result, pandas were caged at any sign of decline(Akku Sony VAIO VGN-FZ11M), and suffered from terrible conditions. Because of pollution and destruction of their natural habitat, along with segregation caused by caging, reproduction of wild pandas was severely limited. In the 1990s, however, several laws (including gun control and the removal of resident humans from the reserves) helped the chances of survival for pandas. With these renewed efforts and improved conservation methods(Akku Sony VAIO VGN-FZ11S), wild pandas have started to increase in numbers in some areas, even though they still are classified as a rare species.

In 2006, scientists reported that the number of pandas living in the wild may have been underestimated at about 1,000. Previous population surveys had used conventional methods to estimate the size of the wild panda population, but using a new method that analyzes DNA from panda droppings, scientists believe that the wild panda population may be as large as 3,000. (Akku Sony VAIO VGN-FZ11Z) Although the species is still endangered, it is thought that the conservation efforts are working. In 2006, there were 40 panda reserves in China, compared to just 13 reserves two decades ago.[10]

The giant panda is among the world's most adored and protected rare animals, and is one of the few in the world whose natural inhabitant status was able to gain a UNESCO World Heritage Site designation. The Sichuan Giant Panda Sanctuaries(Akku Sony VAIO VGN-FZ130E/B), located in the southwest Sichuan province and covering seven natural reserves, were inscribed onto the World Heritage List in 2006.[60][61]

Not all conservationists agree that the money spent on conserving pandas is money well spent. Chris Packham has argued that breeding pandas in captivity is "pointless" because "there is not enough habitat left to sustain them".[62] Packham argues that the money spent on pandas would be better spent elsewhere, (Akku Sony VAIO VGN-FZ140E) [62] and has said that he would "eat the last panda if I could have all the money we have spent on panda conservation put back on the table for me to do more sensible things with,"[63] though he has apologized for upsetting people who like pandas.[64] He points out that "The panda is possibly one of the grossest wastes of conservation money in the last half century." (Akku Sony VAIO VGN-FZ21E)

In 2012, Earthwatch Institute, a global non-profit that teams volunteers with scientists to conduct important environmental research, launched a program called "On the Trail of Giant Panda." This program, based in the Wolong National Nature Reserve, allows volunteers to work up close with pandas cared for in captivity, and help them adapt to life in the wild, so that they may breed, and live longer and healthier lives(Akku Sony VAIO VGN-FZ21J).

Reproduction

Panda Research and Breeding Centre in Chengdu.

Initially the primary method of breeding giant pandas in captivity was by artificial insemination, as they seemed to lose their interest in mating once they were captured.[66] This led some scientists to try extreme methods such as showing them videos of giant pandas mating[67] and giving the males Viagra.[68] Only recently have researchers started having success with captive breeding programs(Akku Sony VAIO VGN-FZ21M), and they have now determined that giant pandas have comparable breeding to some populations of the American black bear, a thriving bear family. The current reproductive rate is considered one young every two years.[12][24]

Giant pandas reach sexual maturity between the ages of four and eight, and may be reproductive until age 20.[69] The mating season is between March and May(Akku Sony VAIO VGN-FZ21S), when a female goes into her estrous cycle which lasts for two or three days and only occurs once a year.[70] When mating, the female is in a crouching, head-down position as the male mounts her from behind. Copulation time is short, ranging from thirty seconds to five minutes, but the male may mount her repeatedly to ensure successful fertilization. The gestation period ranges from 95 to 160 days. (Akku Sony VAIO VGN-FZ21Z)

If twins are born, usually only one survives in the wild. The mother will select the stronger of the cubs, and the weaker will die. It is thought that the mother cannot produce enough milk for two cubs since she does not store fat.[71] The father has no part in helping raise the cub.

When the cub is first born, it is pink, blind, and toothless,[72] weighing only 90 to 130 grams (3.2 to 4.6 ounces), or about 1/800 of the mother's weight. (Akku Sony VAIO VGN-FZ38M) It nurses from its mother's breast 6 to 14 times a day for up to 30 minutes at a time. For three to four hours, the mother may leave the den to feed, which leaves the cub defenseless. One to two weeks after birth, the cub's skin turns gray where its hair will eventually become black. A slight pink color may appear on cub's fur, as a result of a chemical reaction between the fur and its mother's saliva(Akku Sony VAIO VGN-FZ31E). A month after birth, the color pattern of the cub's fur is fully developed. A cub's fur is very soft and coarsens with age. The cub begins to crawl at 75 to 80 days;[43] mothers play with their cubs by rolling and wrestling with them. The cubs are able to eat small quantities of bamboo after six months,[73] though mother's milk remains the primary food source for most of the first year(Akku Sony VAIO VGN-FZ31J). Giant panda cubs weigh 45 kg (100 pounds) at one year, and live with their mothers until they are 18 months to two years old. The interval between births in the wild is generally two years.

In July 2009, Chinese scientists confirmed the birth of the first cub to be successfully conceived through artificial insemination using frozen sperm.[74] The cub was born at 07:41 on 23 July that year in Sichuan as the third cub of You You, an 11-year-old. (Akku Sony VAIO VGN-FZ31M)The technique for freezing the sperm in liquid nitrogen was first developed in 1980 and the first birth was hailed as a solution to the problem of lessening giant panda semen availability which had led to in-breeding.[76][77] It has been suggested that panda semen, which can be frozen for decades, could be shared between different zoos to save the species. Sony VAIO PCG-8131M battery It is expected that zoos in destinations such as San Diego in the United States and Mexico City will now be able to provide their own semen to inseminate more giant pandas.[77]

Attempts have also been made to reproduce giant pandas by interspecific pregnancy by implanting cloned panda embryos into the uterus of an animal of another species. This has resulted in panda fetuses, but no live births. Sony VAIO PCG-8152M battery

Name

There is no conclusive explanation of the origin of the word "panda". The closest candidate is the Nepali word ponya, possibly referring to the adapted wrist bone. The Western world originally applied this name to the red panda. Until 1901, when it was erroneously stated that it was related to the red panda, the giant panda was known as "mottled bear" (Ailuropus melanoleucus) or "particolored bear".Sony VAIO PCG-31311M battery

In most encyclopedic sources, the name "panda" or "common panda" originally referred to the lesser-known red panda,[80] thus necessitating the inclusion of "giant" and "lesser/red" prefixes in front of the names. Even in 2010, the Encyclopædia Britannica still used "giant panda" or "panda bear" for the bear[81] and simply "panda" for the Ailuridae,[82] despite the popular usage of the word "panda"Sony VAIO PCG-31111M battery.

Since the earliest collection of Chinese writings, the Chinese language has given the bear 20 different names, such as 花熊 (huā xióng) "spotted bear" and 竹熊 (zhú xióng) "bamboo bear".[83] The most popular names in China today are 大熊貓 (dà xióng māo), literally "large bear cat", or just 熊貓 (xióng māo), "bear cat"Sony VAIO PCG-8112M battery. The name may have been inspired by the giant panda's eyes, which have pupils that are cat-like vertical slits – unlike other bear species, which have round pupils.[84]

In Taiwan, the popular name for panda is the inverted 貓熊 (māo xióng) "cat bear," even though many encyclopedia and dictionaries in Taiwan still use "bear cat" as the correct name. Some linguists argue that, in this construction, "bear" instead of "cat" is the base noun, making this name more grammatically and logically correct, which may have led to the popular choice despite official writings. Sony VAIO PCG-7186M battery

In zoos

See also: Category:Individual giant pandas

Pandas have been kept in zoos as early as the Western Han Dynasty in China, where the writer Sima Xiangru notes that the panda was the most treasured animal in the emperor's garden of exotic animals in the capital Chang'an (present Xi'an). Not until the 1950s were pandas again recorded to have been exhibited in China's zoos. Sony VAIO PCG-7171M battery

Chi Chi at the London Zoo became very popular. This influenced the World Wildlife Fund to use a panda as its symbol.[86]

A 2006 New York Times article[87] outlined the economics of keeping pandas, which costs five times more than that of the next most expensive animal, an elephant. American zoos generally pay the Chinese government $1 million a year in fees, as part of a typical ten-year contractSony VAIO PCG-9Z1M battery. San Diego's contract with China was to expire in 2008 but got a five-year extension at about half of the previous yearly cost.[88] The last contract, with the Memphis Zoo in Memphis, Tennessee, ends in 2013.

Asia

China

Tai Shan in June 2007

Many zoos and breeding centers in China house giant pandas. These include:

Beijing Zoo – home of the internationally notorious Gu Gu.

Bifengxia Panda Base, Ya'an, Sichuan – home to U.S. born giant pandas Mei Sheng (M), Hua Mei (F), Tai Shan (M),[90] Su Lin (F),[91] and Zhen Zhen (F).[91] It is also home to the Austrian-born Fu Long. Sony VAIO PCG-5S1M battery

Chengdu Research Base of Giant Panda Breeding, Chengdu, Sichuan – Twelve cubs were born here in 2006. It is also home to Japanese-born Xiong Bang (M) and U.S.-born Mei Lan (F).

China Conservation and Research Center for the Giant Panda at the Wolong National Nature Reserve, Sichuan – Seventeen cubs were born here in 2006.[93]

Ocean Park, Hong Kong – home to Jia Jia (F), An An (M), Le Le (M), and Ying Ying (F). Sony VAIO PCG-5P1M battery

Other places in Asia

Taipei Zoo, Taipei, Taiwan – home to Tuan Tuan (M) and Yuan Yuan (F).[97]

Chiang Mai Zoo, Chiang Mai, Thailand – home to Chuang Chuang (M), Lin Hui (F), and Lin Bing, a female cub born 27 May 2009[98][99]

Adventure World, Shirahama, Wakayama – Until recently, home to Ei Mei (M), Mei Mei (F), Rau Hin (F), Ryu Hin and Syu Hin (male twins), and Kou Hin (M). In December 2006, twin cubs were born to Ei Mei and Mei Mei. Two cubs, Eiihin (M) and Meihin (F) Sony VAIO PCG-5N2M battery, were born to Rau Hin on 13 September 2008. Mei Mei, a mother of ten cubs, died on 15 October 2008.

Oji Zoo, Kobe, Hyōgo – home of Kou Kou (M), Tan Tan (F)[104]

River Safari, a new park under Wildlife Reserves Singapore, Singapore – to receive two pandas (Kai Kai and Jia Jia) in 2012.

Australia

Adelaide Zoo, Adelaide – home to Wang Wang (M) and Funi (F). They arrived on 28 November 2009, and went on display on 14 December. They are expected to stay for a minimum of 10 years, and are the only giant pandas living in the Southern Hemisphere. Sony VAIO PCG-3C2M battery

Europe

Giant panda in Vienna’s zoo Tiergarten Schönbrunn

Zoologischer Garten Berlin, Berlin, Germany – home of Bao Bao, age 32,[107] the oldest male panda living in captivity; he has been in Berlin for 25 years and has never reproduced.

Tiergarten Schönbrunn, Vienna, Austria – home to Yang Yang (F) and Long Hui (M), born in Wolong, China in 2000. They gave birth to Fu Long (M) in 2007,[108] and Fu Hu (M) in 2010. Fu Long, who has been relocated to China, was the first to be born in Europe in 25 years. Sony VAIO PCG-8161M battery

Zoo Aquarium, Madrid, Spain – home of Bing Xing (M) and Hua Zuiba (F) since 2007. They gave birth to twin cubs on 7 September 2010. The zoo was also the site of the first giant panda birth in Europe, back in 1982. That giant panda cub was named Chu-lin.

The Edinburgh Zoo – home to Tian Tian (F) and Yang Guang (M) since 4 December 2011.

ZooParc de Beauval – home to Huan Huan (F) and Yuan Zi (M) since 15 Jan 2012Sony VAIO PCG-8141M battery.

North America

Bai Yun at San Diego Zoo, has given birth to 5 cubs in captivity and is considered one of the most successfully reproductive captive pandas

Chapultepec Zoo, Mexico City – home of Xiu Hua, born on 25 June 1985, Shuan Shuan, born on 15 June 1987, and Xin Xin, born on 1 July 1990 from Tohui (Tohui born on Chapultepec Zoo on 21 July 1981 and died on 16 November 1993), all females.

San Diego Zoo, San Diego – home of Bai Yun (F), Gao Gao (M), and Yun Zi (M).

National Zoo in Washington, D.C. – home of Mei Xiang (F) and Tian Tian (M) Sony VAIO PCG-3J1M battery.

Zoo Atlanta, Atlanta – home of Lun Lun (F), Yang Yang (M), Xi Lan (M), and Po (M), born 3 November 2010.[118]

Memphis Zoo, Memphis – home of Ya Ya (F) and Le Le (M)

The Toronto Zoo and Calgary Zoo will receive a pair of pandas named Er Shun (M) and Ji Li (F). The two pandas are expected to start their time in Canada at the Toronto Zoo sometime in 2013 and will spend 10 years in Canada, evenly split between Toronto and Calgary (5 years each).[120]

North American–born pandasSony VAIO PCG-3H1M battery

Tohui (Nahuatl word for kid), born 21 July 1981, died 16 November 1993; female. Chapultepec Zoo, Mexico City. Was the first giant panda that was born and survived in captivity outside China. Her parents were Ying Ying and Pe Pe.

Hua Mei, born 1999 in the San Diego Zoo and sent to China 2004.

Mei Sheng, born 2003 at the San Diego Zoo, sent to China 2007.

Tai Shan, born 9 July 2005 at the National Zoo in Washington, D.C., sent to China 2010.

Su Lin, born 2 August 2005 at the San Diego Zoo and moved to China 2010.

Mei Lan, born 6 September 2006 at Zoo Atlanta, sent to China 2010Sony VAIO PCG-3F1M battery.

Zhen Zhen, born 3 August 2007 at the San Diego Zoo and moved to China 2010.

Xi Lan, born 30 August 2008 at Zoo Atlanta.

Yun Zi, born 5 August 2009 at the San Diego Zoo.

In popular culture

For complete list see: Panda_(disambiguation)

A drawing depicting a panda

Franz Camenzind shot the first sequences of pandas in the wild for American Broadcasting Company (ABC) in about 1982. They were bought by the British Broadcasting Corporation (BBC) Natural History Unit for their weekly magazine show Nature.

In the early 21st century Natural History New Zealand (NHNZ) featured pandas in two documentaries
Sony VAIO PCG-3C1M battery:

Panda Nursery (2006) featured China's Wolong National Nature Reserve in the mountains in Sichuan Province; forty giant pandas and a dedicated team of staff play a crucial role in ensuring the survival of the species. As part of the Reserve’s panda breeding program, a revolutionary new method of rearing twin cubs called ‘swap-raising’ has been developedSony VAIO PCG-9Z2L battery. Each cub is raised by both its natural mother and one of the Reserve’s veterinarians, Wei Rongping, to increase the chances of both cubs surviving.

Growing Up: Giant Panda (2003) featured Chengdu Giant Panda Center in south-west China as one of the best in the world. Yet with female pandas' short fertility cycles and low birth rates, raising the captive panda population is an uphill battleSony VAIO PCG-9Z1L battery.

The tiger (Panthera tigris) is the largest cat species, reaching a total body length of up to 3.3 metres (11 ft) and weighing up to 306 kg (670 lb). They are the third largest land carnivore (behind only the Polar bear and the Brown bear). Their most recognizable feature is a pattern of dark vertical stripes on reddish-orange fur with lighter underparts(Dell 1691P battery). They have exceptionally stout teeth, and their canines are the longest among living felids with a crown height of as much as 74.5 mm (2.93 in) or even 90 mm (3.5 in).[4] In zoos, tigers have lived for 20 to 26 years, which also seems to be their longevity in the wild.[5] They are territorial and generally solitary but social animals, often requiring large contiguous areas of habitat that support their prey requirements(Dell 310-6321 battery). This, coupled with the fact that they are indigenous to some of the more densely populated places on Earth, has caused significant conflicts with humans.

Tigers once ranged widely across Asia, from Turkey in the west to the eastern coast of Russia. Over the past 100 years, they have lost 93% of their historic range, and have been extirpated from southwest and central Asia, from the islands of Java and Bali(Dell 312-0068 battery), and from large areas of Southeast and Eastern Asia. Today, they range from the Siberian taiga to open grasslands and tropical mangrove swamps. The remaining six tiger subspecies have been classified as endangered by IUCN. The global population in the wild is estimated to number between 3,062 to 3,948 individuals, with most remaining populations occurring in small pockets that are isolated from each other(Dell 312-0078 battery). Major reasons for population decline include habitat destruction, habitat fragmentation and poaching.[1] The extent of area occupied by tigers is estimated at less than 1,184,911 km2 (457,497 sq mi), a 41% decline from the area estimated in the mid-1990s.[6]

Tigers are among the most recognisable and popular of the world's charismatic megafauna. They have featured prominently in ancient mythology and folklore, and continue to be depicted in modern films and literature(Dell 312-0079 battery). Tigers appear on many flags, coats of arms, and as mascots for sporting teams.[7] The Bengal tiger is the national animal of Bangladesh and India.

Taxonomy and etymology

In 1758, Linnaeus first described the species in his work Systema Naturae under the scientific name Felis tigris.[3] In 1929, the British taxonomist Reginald Innes Pocock subordinated the species under the genus Panthera using the scientific name Panthera tigris. (Dell 312-0305 battery)

The word Panthera is probably of Oriental origin and retraceable to the Ancient Greek word panther, the Latin word panthera, the Old French word pantere, most likely meaning "the yellowish animal", or from pandarah meaning whitish-yellow. The derivation from Greek pan- ("all") and ther ("beast") may be folk etymology that led to many curious fables. (Dell 312-0326 battery)

The word "tiger" is retraceable to the Latin word tigris meaning a spotted tigerhound of Actaeon.[11] The Greek word tigris is possibly derived from a Persian source.[12]

Range of the tiger in 1900 and 1990

Characteristics and evolution

Video from the Disney's Animal Kingdom

The oldest remains of a tiger-like cat, called Panthera palaeosinensis, have been found in China and Java. This species lived about 2 million years ago, at the beginning of the Pleistocene, and was smaller than a modern tiger. The earliest fossils of true tigers are known from Java(Dell 312-0518 battery), and are between 1.6 and 1.8 million years old. Distinct fossils from the early and middle Pleistocene were also discovered in deposits from China, and Sumatra. A subspecies called the Trinil tiger (Panthera tigris trinilensis) lived about 1.2 million years ago and is known from fossils found at Trinil in Java.[13]

Tigers first reached India and northern Asia in the late Pleistocene, reaching eastern Beringia (but not the American Continent) (Dell 312-0566 battery), Japan, and Sakhalin. Fossils found in Japan indicate that the local tigers were, like the surviving island subspecies, smaller than the mainland forms. This may be due to the phenomenon in which body size is related to environmental space (see insular dwarfism), or perhaps the availability of prey. Until the Holocene, tigers also lived in Borneo, as well as on the island of Palawan in the Philippines. (Dell 312-0585 battery)

Characteristics

Siberian tiger

Tigers have muscular bodies with particularly powerful forelimbs and large heads. The pelage coloration varies between shades of orange or brown with white ventral areas and distinctive black stripes. The face has long whiskers, which are especially long in males. The pupils are circular with yellow irises. The small, rounded ears have black markings on the back(Dell 312-0831 battery), surrounding a white spot.[4] These spots, called ocelli, play an important role in intraspecific communication.[15]

The pattern of stripes is unique to each animal, these unique markings can be used by researchers to identify individuals (both in the wild and captivity), much in the same way that fingerprints are used to identify humans. It seems likely that the function of stripes is camouflage(Dell BAT30WL battery), serving to help tigers conceal themselves amongst the dappled shadows and long grass of their environment as they stalk their prey. The stripe pattern is also found on the skin of the tiger. If a tiger were to be shaved, its distinctive camouflage pattern would be preserved.

Skeleton

The tiger are the most variable in size of all big cats, even more so than the leopard and much more so than lions.[16] The Bengal, Caspian and Siberian tiger subspecies represent the largest living felids, and rank among the biggest felids that ever existed(Dell D6400 battery). An adult male tiger from Northern India or Siberia outweighs an average male lion by around 45 kg (99 lb).[16] Females vary in length from 200 to 275 cm (79 to 108 in), weigh 65 to 167 kg (140 to 370 lb) with a greatest length of skull ranging from 268 to 318 mm (10.6 to 12.5 in). Males vary in size from 250 to 330 cm (98 to 130 in), weigh 90 to 306 kg (200 to 670 lb) with a greatest length of skull ranging from 316 to 383 mm (12.4 to 15.1 in). (Dell HF674 battery) Body size of different populations seems to be correlated with climate—Bergmann's Rule—and can be explained from the point of view of thermoregulation.[4] Large male Siberian tigers can reach a total length of more than 3.5 m (11.5 ft) "over curves", 3.3 m (10.8 ft) "between pegs" and a weight of 306 kg (670 lb). This is considerably larger than the size reached by the smallest living tiger subspecies(Dell N3010 battery), the Sumatran tiger, which reach a body weight of 75 to 140 kg (170 to 310 lb). Of the total length of a tiger, the tail comprises 0.6 to 1.1 m (2.0 to 3.6 ft). At the shoulder, tigers may variously stand 0.7 to 1.22 m (2.3 to 4.0 ft) tall.[5]

Tigresses are smaller than the males in each subspecies, although the size difference between male and female tigers tends to be more pronounced in the larger tiger subspecies, with males weighing up to 1.7 times more than the females(Dell Inspiron N4010 battery).[20] In addition, male tigers have wider forepaw pads than females. Biologists use this difference to determine gender based on tiger tracks.[21] The skull of the tiger is very similar to that of the lion, though the frontal region is usually not as depressed or flattened, with a slightly longer postorbital region. The skull of a lion has broader nasal openings(Dell INSPIRON 1100 battery). However, due to the amount of skull variation in the two species, usually, only the structure of the lower jaw can be used as a reliable indicator of species.[22]

Subspecies

A Bengal tiger with a cub.

There are nine subspecies of tiger, three of which are extinct. Their historical range in Bangladesh, Siberia, Iran, Afghanistan, India, China, and southeast Asia, including three Indonesian islands is severely diminished today. The surviving subspecies, in descending order of wild population(Dell Inspiron 1200 battery), are:

The Bengal tiger (Panthera tigris tigris) lives in India, Nepal, Bhutan and Bangladesh, and is the most common subspecies with populations estimated at less than 2,500 adult individuals. In 2011 the total population of adult tigers is estimated at 1,520–1,909 in India, 440 in Bangladesh, 155 in Nepal and 75 in Bhutan.[23] It lives in alluvial grasslands(Dell Inspiron 1420 battery), subtropical and tropical rainforests, scrub forests, wet and dry deciduous forests, and mangroves. Male Bengal tigers had a total length, including the tail, of 270 to 310 cm (110 to 120 in), while females range from 240 to 265 cm (94 to 104 in). The weight of males range from 175 to 260 kg (390 to 570 lb), while that of the females range from 100 to 181 kg (220 to 400 lb) (Dell Inspiron 1464 battery). In northern India and Nepal, tigers tend to be of larger size. Males often average 235 kilograms (520 lb), while females average 141 kilograms (310 lb).[25] In 1972, Project Tiger was founded in India aiming at ensuring a viable population of tigers in the country and preserving areas of biological importance as a natural heritage for the people.[26] But the illicit demand for bones and body parts from wild tigers for use in Traditional Chinese medicine is the reason for the unrelenting poaching pressure on tigers on the Indian subcontinent. (Dell Inspiron 1564 battery) Between 1994 and 2009, the Wildlife Protection Society of India has documented 893 cases of tigers killed in India, which is just a fraction of the actual poaching and illegal trade in tiger parts during those years.[28] An area of special conservation interest lies in the Terai Arc Landscape in the Himalayan foothills of northern India and southern Nepal(Dell Inspiron 1764 battery), where 11 protected areas comprising dry forest foothills and tall grass savannas harbor tigers in a 49,000 square kilometres (19,000 sq mi) landscape. The goals are to manage tigers as a single metapopulation, the dispersal of which between core refuges can help maintain genetic, demographic, and ecological integrity, and to ensure that species and habitat conservation becomes mainstreamed into the rural development agenda(Dell Inspiron 1520 battery). In Nepal, a community-based tourism model has been developed with a strong emphasis on sharing benefits with local people and on the regeneration of degraded forests. The approach has been successful in reducing poaching, restoring habitats, and creating a local constituency for conservation. (Dell Inspiron 1521 battery)

Indochinese tiger

The Indochinese Tiger (Panthera tigris corbetti), also called Corbett's tiger, is found in Cambodia, China, Laos, Burma, Thailand, and Vietnam. These tigers are smaller and darker than Bengal tigers: Males weigh from 150–190 kg (330–420 lb) while females are smaller at 110–140 kg (240–310 lb). Their preferred habitat is forests in mountainous or hilly regions(Dell inspiron 1525 battery). According to government estimates of national tiger populations, the subspecies numbers around a total of 350 individuals.[30] All existing populations are at extreme risk from poaching, prey depletion as a result of poaching of primary prey species such as deer and wild pigs, habitat fragmentation and inbreeding. In Vietnam, almost three-quarters of the tigers killed provide stock for Chinese pharmacies(Dell inspiron 1526 battery).

Malayan tiger

The Malayan Tiger (Panthera tigris jacksoni), exclusively found in the southern part of the Malay Peninsula, was not considered a subspecies in its own right until 2004. The new classification came about after a study by Luo et al. from the Laboratory of Genomic Diversity Study,[31] part of the National Cancer Institute of the United States. According to official government figures(Dell Inspiron 1720 battery), the population in the wild may number around 500 individuals, but is under considerable poaching pressure. The Malayan tiger is the smallest of the mainland tiger subspecies, and the second smallest living subspecies, with males averaging about 120 kg (260 lb) and females about 100 kg (220 lb) in weight. The Malayan tiger is a national icon in Malaysia, appearing on its coat of arms and in logos of Malaysian institutions, such as Maybank(Dell Inspiron 2000 battery).

Sumatran tiger

Siberian tiger

The Sumatran Tiger (Panthera tigris sumatrae) is found only on the Indonesian island of Sumatra, and is critically endangered.[32] It is the smallest of all living tiger subspecies, with adult males weighing between 100–140 kg (220–310 lb) and females 75–110 kg (170–240 lb).[33] Their small size is an adaptation to the thick, dense forests of the island of Sumatra where they reside(Dell INSPIRON 2600 battery), as well as the smaller-sized prey. The wild population is estimated at between 400 and 500, seen chiefly in the island's national parks. Recent genetic testing has revealed the presence of unique genetic markers, indicating that it may develop into a separate species,[specify] if it does not go extinct.[34] This has led to suggestions that Sumatran tigers should have greater priority for conservation than any other subspecies(Dell INSPIRON 3800 battery). While habitat destruction is the main threat to existing tiger population (logging continues even in the supposedly protected national parks), 66 tigers were recorded as being shot and killed between 1998 and 2000, or nearly 20% of the total population.

The Siberian tiger (Panthera tigris altaica), also known as the Amur tiger, inhabits the Amur-Ussuri region of Primorsky Krai and Khabarovsk Krai in far eastern Siberia. (Dell INSPIRON 4000 battery)It ranks among the biggest felids that have ever existed with a head and body length of 160–180 cm (63–71 in) for females and 190–230 cm (75–91 in) for males, plus a tail of about 60–110 cm (24–43 in) and an average weight of around 227 kg (500 lb) for males. Siberian tigers have thick coats and a paler golden hue and fewer stripes.[4] The heaviest wild Siberian tiger weighed 384 kg (850 lb) but according to Mazák this record is not reliable. (Dell Inspiron 5000 battery) In 2005, there were 331–393 adult-subadult Siberian tigers in the region, with a breeding adult population of about 250 individuals. The population has been stable for more than a decade, but partial surveys conducted after 2005 indicate that the Russian tiger population is declining.[36] At the turn of the century, the phylogenetic relationships of tiger subspecies was re-assessed(Dell INSPIRON 500M battery), and a remarkable similarity between the Siberian and Caspian tiger observed indicating that the Siberian tiger population is the genetically closest living relative of the extinct Caspian tiger, and strongly implying a very recent common ancestry for the two groups.[37]

South China tiger

The South China tiger (Panthera tigris amoyensis), also known as the Amoy or Xiamen tiger, is the most critically endangered subspecies of tiger and is listed as one of the 10 most endangered animals in the world. (Dell INSPIRON 5100 battery) One of the smaller tiger subspecies, the length of the South China tiger ranges from 2.2–2.6 m (87–100 in) for both males and females. Males weigh between 127 and 177 kg (280 and 390 lb) while females weigh between 100 and 118 kg (220 and 260 lb). From 1983 to 2007, no South China tigers were sighted.[39] In 2007 a farmer spotted a tiger and handed in photographs to the authorities as proof. (Dell INSPIRON 510M battery) The photographs in question, however, were later exposed as fake, copied from a Chinese calendar and digitally altered, and the "sighting" turned into a massive scandal.

In 1977, the Chinese government passed a law banning the killing of wild tigers, but this may have been too late to save the subspecies, since it is possibly already extinct in the wild. There are currently 59 known captive South China tigers(Dell INSPIRON 6000 battery), all within China, but these are known to be descended from only six animals. Thus, the genetic diversity required to maintain the subspecies may no longer exist.[citation needed] Currently, there are breeding efforts to reintroduce these tigers to the wild.

Extinct subspecies

A hunted down Bali tiger

A photograph of a Javan tiger.

A captive Caspian tiger, Berlin Zoological Garden 1899

The Bali tiger (Panthera tigris balica) was limited to the Indonesian island of Bali, and was the smallest subspecies with a weight of 90–100 kg (200–220 lb) in males and 65–80 kg (140–180 lb) in females. (Dell INSPIRON 600M battery) Bali tigers were hunted to extinction — the last Bali tiger, an adult female, is thought to have been killed at Sumbar Kima, West Bali on 27 September 1937. There is no Bali tiger in captivity. The tiger still plays an important role in Balinese Hinduism.

The Caspian tiger (Panthera tigris virgata), also known as the Hyrcanian tiger or Turan tiger was found in the sparse forest habitats and riverine corridors west and south of the Caspian Sea and west through Central Asia into the Takla-Makan desert of Xinjiang(Dell Inspiron 6400 battery), and has been recorded in the wild until the early 1970s.[44] The Amur tiger is the genetically closest living relative of the Caspian tiger.[37]

The Javan tiger (Panthera tigris sondaica) was limited to the island of Java, and has been recorded until the mid-1970s.[45] Javan tigers were larger than Bali tigers; males weighed 100–140 kg (220–310 lb) and females 75–115 kg (170–250 lb).[46] After 1979, there were no more confirmed sightings in the region of Mount Betiri. (Dell INSPIRON 7000 battery)An expedition to Mount Halimun Salak National Park in 1990 did not yield any definite, direct evidence for the continued existence of tigers.[48]

Hybrids

Further information: Panthera hybrid, Liger and Tiglon

Hybridisation among the big cats, including the tiger, was first conceptualised in the 19th century, when zoos were particularly interested in the pursuit of finding oddities to display for financial gain.[49] Lions have been known to breed with tigers (most often the Amur and Bengal subspecies) to create hybrids called ligers and tigons. (Dell INSPIRON 700M battery) Such hybrids were once commonly bred in zoos, but this is now discouraged due to the emphasis on conserving species and subspecies. Hybrids are still bred in private menageries and in zoos in China.

The liger is a cross between a male lion and a tigress.[51] Because the lion sire passes on a growth-promoting gene, but the corresponding growth-inhibiting gene from the female tiger is absent, ligers grow far larger than either parent(Dell Inspiron 710m battery). They share physical and behavioural qualities of both parent species (spots and stripes on a sandy background). Male ligers are sterile, but female ligers are often fertile. Males have about a 50% chance of having a mane, but, even if they do, their manes will be only around half the size of that of a pure lion. Ligers are typically between 10 to 12 feet in length, and can be between 800 and 1,000 pounds or more. (Dell INSPIRON 8200 battery)

The less common tigon is a cross between the lioness and the male tiger.[52]

Colour variations

White tigers

Main article: White tiger

A Bengal white tiger in Bannerghatta National Park in Bangalore

A pair of white tigers at the Singapore Zoo.

There is a well-known allele that produces the white tiger, technically known as chinchilla albinistic,[53] an animal which is rare in the wild, but widely bred in zoos due to its popularity. Breeding of white tigers will often lead to inbreeding (as the trait is recessive). Many initiatives have taken place in white and orange tiger mating in an attempt to remedy the issue(Dell INSPIRON 8600 battery), often mixing subspecies in the process. Such inbreeding has led to white tigers having a greater likelihood of being born with physical defects, such as cleft palates and scoliosis (curvature of the spine).[54][55] Furthermore, white tigers are prone to having crossed eyes (a condition known as strabismus). Even apparently healthy white tigers generally do not live as long as their orange counterparts(Dell INSPIRON 9100 battery). Recordings of white tigers were first made in the early 19th century.[56] They can only occur when both parents carry the rare gene found in white tigers; this gene has been calculated to occur in only one in every 10,000 births. The white tiger is not a separate sub-species, but only a colour variation; since the only white tigers that have been observed in the wild have been Bengal tigers[57] (and all white tigers in captivity are at least part Bengal) (Dell INSPIRON 9200 battery), it is commonly thought that the recessive gene that causes the white colouring is probably carried only by Bengal tigers, although the reasons for this are not known.[54][58] Nor are they in any way more endangered than tigers are generally, this being a common misconception. Another misconception is that white tigers are albinos, despite the fact that pigment is evident in the white tiger's stripes(Dell INSPIRON 9300 battery). They are distinct not only because of their white hue; they also have blue eyes.

Golden tigers

Main article: Golden tiger

A rare golden tiger at the Buffalo Zoo.

In addition, another recessive gene may create a very unusual "golden" or "golden tabby" colour variation, sometimes known as "strawberry." Golden tigers have light gold fur, pale legs and faint orange stripes. Their fur tends to be much thicker than normal.[59] There are extremely few golden tigers in captivity, around 30 in all(Dell Inspiron 9400 battery). Like white tigers, golden tigers are invariably at least part Bengal. Some golden tigers carry the white tiger gene, and when two such tigers are mated, can produce some stripeless white offspring. Both white and golden tigers tend to be larger than average Bengal tigers.

Other colour variations

There is no authenticated case of a black tiger, with the possible exception of one dead specimen examined in Chittagong in 1846. (Dell Inspiron E1505 battery) There are unconfirmed reports of a "blue" or slate-coloured tiger, the Maltese tiger. Largely or totally black tigers are assumed, if real, to be intermittent mutations rather than distinct species.[53]

Distribution and habitat

In the past, tigers were found throughout Asia, from the Caucasus and the Caspian Sea to Siberia and the Indonesian islands of Java, Bali and Sumatra. During the 20th century, tigers have been extirpated in western Asia and became restricted to isolated pockets in the remaining parts of their range(Dell Inspiron E1705 battery). Today, their fragmented and partly degraded range extends from India in the west to China and Southeast Asia. The northern limit of their range is close to the Amur River in south eastern Siberia. The only large island inhabited by tigers today is Sumatra.[1]

Tigers were extirpated on the island of Bali in the 1940s, around the Caspian Sea in the 1970s, and on Java in the 1980s. Loss of habitat and the persistent killing of tigers and tiger prey precipitated these extirpations(Dell Inspiron Mini 9 battery), a process that continues to leave forests devoid of tigers and other large mammals across South and Southeast Asia. Since the beginning of the 21st century, their historical range has shrunk by 93%. In the decade from 1997 to 2007, the estimated area known to be occupied by tigers has declined by 41%.[2]

Fossil remains indicate that tigers were present in Borneo and Palawan in the Philippines during the late Pleistocene and Holocene. (Dell Latitude D400 battery)

Tiger habitats will usually include sufficient cover, proximity to water, and an abundance of prey. Bengal tigers live in many types of forests, including wet, evergreen, the semi-evergreen of Assam and eastern Bengal; the mangrove forest of the Ganges Delta; the deciduous forest of Nepal, and the thorn forests of the Western Ghats. Compared to the lion, the tiger prefers denser vegetation(Dell STUDIO 1450 battery), for which its camouflage colouring is ideally suited, and where a single predator is not at a disadvantage compared with the multiple felines in a pride.

Biology and behaviour

Territorial behaviour

Adult tigers lead solitary lives and congregate only on an ad hoc and transitory basis when special conditions permit, such as plentiful supply of food. They establish and maintain home ranges. Resident adults of either sex tend to confine their movements to a definite area of habitat(Dell Vostro 1400 battery), within which they satisfy their needs, and in the case of tigresses, those of their growing cubs. Those sharing the same ground are well aware of each other's movements and activities.[60]

The size of a tiger's home range mainly depends on prey abundance, and, in the case of male tigers, on access to females. A tigress may have a territory of 20 km2 (7.7 sq mi), while the territories of males are much larger, covering 60 to 100 km2 (23 to 39 sq mi). The range of a male tends to overlap those of several females. (Dell Vostro 1500 battery)

Tigers are strong swimmers, and are often found bathing in ponds, lakes, and rivers. During the extreme heat of the day, they often cool off in pools. They are able to carry prey through the water.

Tigers for the most part are solitary animals.

The relationships between individuals can be quite complex, and it appears that there is no set "rule" that tigers follow with regards to territorial rights and infringing territories. For instance(Dell XPS GEN 2 battery), although for the most part tigers avoid each other, both male and female tigers have been documented sharing kills. George Schaller observed a male tiger share a kill with two females and four cubs. Females are often reluctant to let males near their cubs, but Schaller saw that these females made no effort to protect or keep their cubs from the male, suggesting that the male might have been the father of the cubs(Dell XPS M1210 battery). In contrast to male lions, male tigers will allow the females and cubs to feed on the kill first. Furthermore, tigers seem to behave relatively amicably when sharing kills, in contrast to lions, which tend to squabble and fight. Unrelated tigers have also been observed feeding on prey together. The following quotation is from Stephen Mills' book Tiger, as he describes an event witnessed by Valmik Thapar and Fateh Singh Rathore in Ranthambhore National Park: (Dell XPS M1330 battery)

A dominant tigress they called Padmini killed a 250 kg (550 lb) male nilgai – a very large antelope. They found her at the kill just after dawn with her three 14-month-old cubs and they watched uninterrupted for the next ten hours. During this period the family was joined by two adult females and one adult male – all offspring from Padmini's previous litters and by two unrelated tigers, one female the other unidentified(Dell XPS 1340 battery). By three o'clock there were no fewer than nine tigers round the kill.

When young female tigers first establish a territory, they tend to do so fairly close to their mother's area. The overlap between the female and her mother's territory tends to wane with increasing time. Males, however, wander further than their female counterparts, and set out at a younger age to mark out their own area(Dell XPS M1530 battery). A young male will acquire territory either by seeking out a range devoid of other male tigers, or by living as a transient in another male's territory until he is old and strong enough to challenge the resident male. The highest mortality rate (30–35% per year) amongst adult tigers occurs for young male tigers who have just left their natal area, seeking out territories of their own. (Dell XPS M170 battery)

Two male Bengal tiger siblings play with each other in the Pilibhit Tiger Reserve, India.

Tiger dentition (above), compared with that of an Asian black bear (below). The large canines are used to make the killing bite, but they tear meat when feeding using the carnassial teeth.

Male tigers are generally more intolerant of other males within their territory than females are of other females. For the most part, however, territorial disputes are usually solved by displays of intimidation, rather than outright aggression(Dell XPS M1710 battery). Several such incidents have been observed, in which the subordinate tiger yielded defeat by rolling onto its back, showing its belly in a submissive posture.[64] Once dominance has been established, a male may actually tolerate a subordinate within his range, as long as they do not live in too close quarters.[63] The most violent disputes tend to occur between two males when a female is in oestrus, and may result in the death of one of the males(Dell XPS M1730 battery), although this is a rare occurrence.[63][64]

To identify his territory, the male marks trees by spraying of urine and anal gland secretions, as well as marking trails with scat. Males show a grimacing face, called the Flehmen response, when identifying a female's reproductive condition by sniffing their urine markings. Like the other Panthera cats, tigers can roar. Tigers will roar for both aggressive and non-aggressive reasons. Other tiger vocal communications include moans, hisses, growls and chuffs(Dell XPS M2010 battery).

Tigers have been studied in the wild using a variety of techniques. The populations of tigers were estimated in the past using plaster casts of their pugmarks. This method was criticized as being inaccurate.[65] Attempts were made to use camera trapping instead. Newer techniques based on DNA from their scat are also being evaluated. Radio collaring has also been a popular approach to tracking them for study in the wild(Dell Latitude E5400 battery).

Hunting and diet

In the wild, tigers mostly feed on larger and medium sized animals. Sambar, gaur, chital, barasingha, wild boar, nilgai and both water buffalo and domestic buffalo are the tiger's favoured prey in India. Sometimes, they also prey on leopards, pythons, sloth bears and crocodiles. In Siberia the main prey species are manchurian wapiti, wild boar, sika deer, moose, roe deer(Dell Latitude E5500 battery), and musk deer. In Sumatra, sambar, muntjac, wild boar, and malayan tapir are preyed on. In the former Caspian tiger's range, prey included saiga antelope, camels, caucasian wisent, yak, and wild horses. Like many predators, they are opportunistic and will eat much smaller prey, such as monkeys, peafowls, hares, and fish(Dell Latitude E6400 battery).

Adult elephants are too large to serve as common prey, but conflicts between tigers and elephants do sometimes take place. A case where a tiger killed an adult Indian Rhinoceros has been observed. Young elephant and rhino calves are occasionally taken. Tigers also sometimes prey on domestic animals such as dogs, cows, horses, and donkeys. These individuals are termed cattle-lifters or cattle-killers in contrast to typical game-killers. (Dell Latitude E6500 battery)

Old tigers, or those wounded and rendered incapable of catching their natural prey, have turned into man-eaters; this pattern has recurred frequently across India. An exceptional case is that of the Sundarbans, where healthy tigers prey upon fishermen and villagers in search of forest produce, humans thereby forming a minor part of the tiger's diet.[67] Tigers will occasionally eat vegetation for dietary fiber, the fruit of the Slow Match Tree being favoured. (Dell Inspiron Mini 12 battery)

Tiger with kill

Tigers are thought to be nocturnal predators, hunting at night.[68] However, in areas where humans are absent, they have been observed via remote controlled, hidden cameras hunting during the daylight hours.[69] They generally hunt alone and ambush their prey as most other cats do, overpowering them from any angle(Dell XPS M140 battery), using their body size and strength to knock large prey off balance. Even with their great masses, tigers can reach speeds of about 49–65 kilometres per hour (35–40 miles per hour), although they can only do so in short bursts, since they have relatively little stamina; consequently, tigers must be relatively close to their prey before they break their cover. Tigers have great leaping ability(Dell XPS 13 battery); horizontal leaps of up to 10 metres have been reported, although leaps of around half this amount are more typical. However, only one in twenty hunts ends in a successful kill.[68]

When hunting large prey, tigers prefer to bite the throat and use their forelimbs to hold onto the prey, bringing it to the ground. The tiger remains latched onto the neck until its prey dies of strangulation. (Dell XPS 16 battery) By this method, gaurs and water buffalos weighing over a ton have been killed by tigers weighing about a sixth as much.[70] With small prey, the tiger bites the nape, often breaking the spinal cord, piercing the windpipe, or severing the jugular vein or common carotid artery.[71] Though rarely observed, some tigers have been recorded to kill prey by swiping with their paws, which are powerful enough to smash the skulls of domestic cattle,[66] and break the backs of sloth bears. (Dell XPS 1640 battery)

During the 1980s, a tiger named "Genghis" in Ranthambhore National Park was observed frequently hunting prey through deep lake water,[73] a pattern of behaviour that had not been previously witnessed in over 200 years of observations. Moreover, he appeared to be extraordinarily successful for a tiger, with as many as 20% of hunts ending in a kill(Dell XPS 1645 battery).

Reproduction

A tigress with her cubs in the Kanha Tiger Reserve, India.

A Bengal tigress with her cubs at the Bandhavgarh National Park, India

Mating can occur all year round, but is generally more common between November and April.[74] A female is only receptive for a few days and mating is frequent during that time period. A pair will copulate frequently and noisily, like other cats. The gestation period is 16 weeks. The litter size usually consists of around 3–4 cubs of about 1 kilogram (2.2 lb) each(Dell XPS 1647 battery), which are born blind and helpless. The females rear them alone, sheltering them in dens such as thickets and rocky crevices. The father of the cubs generally takes no part in rearing them. Unrelated wandering male tigers may even kill cubs to make the female receptive, since the tigress may give birth to another litter within 5 months if the cubs of the previous litter are lost. (Dell Latitude 131L battery) The mortality rate of tiger cubs is fairly high – approximately half do not survive to be more than two years old.[74]

There is generally a dominant cub in each litter, which tends to be male but may be of either sex.[73] This cub generally dominates its siblings during play and tends to be more active, leaving its mother earlier than usual. At 8 weeks, the cubs are ready to follow their mother out of the den, although they do not travel with her as she roams her territory until they are older(Dell Latitude C400 battery). The cubs become independent around 18 months of age, but it is not until they are around 2–2½ years old that they leave their mother. Females reach sexual maturity at 3–4 years, whereas males reach sexual maturity at 4–5 years.[74]

Over the course of her life, a female tiger will give birth to an approximately equal number of male and female cubs. Tigers breed well in captivity, and the captive population in the United States may rival the wild population of the world. (Dell Latitude C500 battery)

Interspecific predatory relationships

Tiger hunted by wild dogs (dholes) as illustrated in Samuel Howett & Edward Orme, Hand Coloured, Aquatint Engravings, Published London 1807.

Tigers may kill such formidable predators as leopards, pythons and even crocodiles on occasion,[76][77][78] although predators typically avoid one another. When seized by a crocodile, a tiger will strike at the reptile's eyes with its paws. (Dell Latitude C510 battery) Eighteenth century Physician Oliver Goldsmith described the frequent conflicts between mugger crocodiles and tigers that occurred during that time. Thirsty tigers would frequently descend to the rivers to drink and on occasion were seized and killed by the muggers, though more often the tiger escaped and the reptile was disabled.[79] Leopards dodge competition from tigers by hunting in different times of the day and hunting different prey. (Dell Latitude C540 battery) With relatively abundant prey, tigers and leopards were seen to successfully coexist without competitive exclusion or inter-species dominance hierarchies that may be more common to the savanna.[81] Tigers have been known to suppress wolf populations in areas where the two species coexist, mainly via competitive exclusion. (Dell Latitude C600 battery) Dhole packs have been observed to attack and kill tigers in disputes over food, though will rarely take such risks since losses among the pack would be considerable.[72] Lone golden jackals expelled from their pack have been known to form commensal relationships with tigers. These solitary jackals, known as kol-bahl, will attach themselves to a particular tiger, trailing it at a safe distance in order to feed on the big cat's kills(Dell Latitude C610 battery). A kol-bahl will even alert a tiger to a kill with a loud pheal. Tigers have been known to tolerate these jackals: one report describes how a jackal confidently walked in and out between three tigers walking together a few feet away from each other.[84] Siberian tigers and brown bears can be competitors and usually avoid confrontation; however, tigers will kill bear cubs and even some adults on occasion. Bears (Asiatic black bears and brown bears) make up 5–8% of the tiger's diet in the Russian Far East. (Dell Latitude C640 battery) There are also a few records of brown bears killing tigers, either in self defense or in disputes over kills.[22] Some bears emerging from hibernation will try to steal tigers' kills, although the tiger will sometimes defend its kill. Sloth bears are quite aggressive and will sometimes drive young tigers away from their kills, although it is more common for Bengal tigers to prey on sloth bears. (Dell Latitude C800 battery) Tigers may additionally predate the other bear species it encounters (or had encountered historically), which includes Giant pandas and sun bears, but information is very limited on such interactions.[85]

Conservation efforts

For more details on this topic, see Tiger hunting.

Poaching for fur and destruction of habitat have greatly reduced tiger populations in the wild. At the start of the 20th century, it is estimated there were over 100,000 tigers in the world but the population has dwindled to between 1,500 and 3,500 in the wild. (Dell Latitude C810 battery) Demand for tiger parts for the purposes of Traditional Chinese Medicine has also been cited as a threat to tiger populations. Some estimates suggest that there are less than 2,500 mature breeding individuals, with no subpopulation containing more than 250 mature breeding individuals.[1]

India

A Bengal tiger in a national park in southern India. Indian officials successfully reintroduced two Bengal tigers in the Sariska Tiger Reserve in July 2008. (Dell Latitude C840 battery)

Main article: Project Tiger

India is home to the world's largest population of tigers in the wild.[90] According to the World Wildlife Fund, of the 3,500 tigers around the world, 1,400 are found in India. Only 11% of original Indian tiger habitat remains, and it is becoming significantly fragmented and often degraded. (Dell Latitude CPI battery)

A major concerted conservation effort, known as Project Tiger, has been underway since 1973, initially spearheaded by Indira Gandhi. The fundamental accomplishment has been the establishment of over 25 well-monitored tiger reserves in reclaimed land where human development is categorically forbidden(Dell Latitude CPX battery). The program has been credited with tripling the number of wild Bengal tigers from roughly 1,200 in 1973 to over 3,500 in the 1990s. However, a tiger census carried out in 2007, whose report was published on February 12, 2008, stated that the wild tiger population in India declined by 60% to approximately 1,411.[93] It is noted in the report that the decrease of tiger population can be attributed directly to poaching. (Dell Latitude D410 battery)

An Indian Tiger at Guwahati Zoo in Assam, India.

Following the release of the report, the Indian government pledged $153 million to further fund the Project Tiger initiative, set up a Tiger Protection Force to combat poachers, and fund the relocation of up to 200,000 villagers to minimise human-tiger interaction.[95] Additionally, eight new tiger reserves in India were set up. (Dell Latitude D420 battery) Indian officials successfully started a project to reintroduce the tigers into the Sariska Tiger Reserve.[97] The Ranthambore National Park is often cited as a major success by Indian officials against poaching.[98]

Tigers Forever is a collaboration between the Wildlife Conservation Society and Panthera Corporation to serve as both a science-based action plan and a business model to ensure that tigers live in the wild forever(Dell Latitude D430 battery). Initial field sites of Tigers Forever include the world's largest tiger reserve, the 21,756 km2 (8,400 sq mi) Hukaung Valley in Myanmar, the Western Ghats in India, Thailand's Huai Khai Khaeng-Thung Yai protected areas, and other sites in Laos PDR, Cambodia, the Russian Far East and China covering approximately 260,000 km2 (100,000 sq mi) of critical tiger habitat(Dell Latitude D500 battery).

Russia

Tiger headcount in 1990

The Siberian tiger was on the brink of extinction with only about 40 animals in the wild in the 1940s. Under the Soviet Union, anti-poaching controls were strict and a network of protected zones (zapovedniks) were instituted, leading to a rise in the population to several hundred. Poaching again became a problem in the 1990s, when the economy of Russia collapsed(Dell Latitude D505 battery), local hunters had access to a formerly sealed off lucrative Chinese market, and logging in the region increased. While an improvement in the local economy has led to greater resources being invested in conservation efforts, an increase of economic activity has led to an increased rate of development and deforestation. The major obstacle in preserving the species is the enormous territory individual tigers require (up to 450 km2 needed by a single female and more for a single male). (Dell Latitude D510 battery) Current conservation efforts are led by local governments and NGO's in consort with international organisations, such as the World Wide Fund and the Wildlife Conservation Society.[101] The competitive exclusion of wolves by tigers has been used by Russian conservationists to convince hunters in the Far East to tolerate the big cats, as they limit ungulate populations less than wolves(Dell Latitude D520 battery), and are effective in controlling the latter's numbers.[102] Currently, there are about 400–550 animals in the wild.

Tibet

The trade in tiger skins is illegal in the People's Republic of China, of which Tibet is a part. However, the law banning the trade in endangered animal parts is not enforced in Tibet. An undercover investigation in 2000 by the Wildlife Protection Society of India produced much news about the tiger skin trade and pictures of Tibetans wearing tiger skins(Dell Latitude D600 battery). The tigers poached for their skins, subsequent investigations found, originated in India, in a "highly sophisticated" smuggling operation that crossed through Nepal, that "had less to do with old customs than new money" and even attracted European tourists for the tiger skin products of Lhasa. When in 2005, officials in Tibet intercepted "32 tiger, 579 leopard and 665 otter skins"(Dell Latitude D610 battery), the 14th Dalai Lama called on exiled Tibetans, who are involved in the trade, to cease their activity.[103] The 14th Dalai Lama had spoken out about wearing furs before, but he repeated his condemnation during the 2006 Kalachakra festival in India to expatriate Tibetans.[104] Afterwards, the Dalai Lama issued a press release claiming to have received video of Tibetans burning their animal skin coats(Dell Latitude D620 battery), and reports of arrests of eight Tibetans involved for conspiring with the Dalai Lama's government.[105]

Population estimate

The global wild tiger population is estimated at anywhere between 3,062 and 3,948 individuals. The World Wide Fund for Nature estimates the tiger population at 3,200.[106] The exact number of wild tigers is unknown, as many estimates are outdated or come from educated guesses(Dell Latitude D630 battery). Few estimates are considered reliable, coming from comprehensive scientific censuses. The table shows estimates per country according to IUCN and range country governments.

Rewilding

Origin

Although the term "rewilding" was used in conservation in other contexts since at least 1990,[108] it was first applied to the restoration of a single species of carnivores by conservationist and ex-carnivore manager of Pilanesberg National Park, Gus Van Dyk in 2003. (Dell Latitude D800 battery)

In 1978, the Indian conservationist Billy Arjan Singh attempted to rewild the tigress Tara in Dudhwa National Park that was born and reared in a zoo.[109] This was soon followed by a large number of people being eaten by a tigress who was later shot. Government officials claim that this tigress was Tara, an assertion hotly contested by Singh and conservationists(Dell Latitude D810 battery). Later on, this rewilding gained further disrepute when it was found that the local gene pool had been sullied by Tara's introduction as she was partly Siberian tiger, a fact not known at the time of release, ostensibly due to poor record-keeping at Twycross Zoo, where she had been raised.

Save China's Tigers

A South China tiger of the Save China's Tigers project with his blesbuck kill

Main article: Save China's Tigers(Dell Latitude D820 battery)

The organisation Save China's Tigers, working with the Wildlife Research Centre of the State Forestry Administration of China and the Chinese Tigers South Africa Trust, secured an agreement on the reintroduction of Chinese tigers into the wild. The agreement, which was signed in Beijing on 26 November 2002, calls for the establishment of a Chinese tiger conservation model through the creation of a pilot reserve in China where indigenous wildlife(Dell Latitude D830 battery), including the South China Tiger, will be reintroduced. Save China's Tigers aims to rewild the critically endangered South China Tiger by bringing a few captive-bred individuals to South Africa for rehabilitation training for them to regain their hunting instincts. At the same time, a pilot reserve in China is being set up and the Tigers will be relocated and release back in China when the reserve in China is ready. (Dell Latitude 2100 battery)The offspring of the trained tigers will be released into the pilot reserves in China, while the original animals will stay in South Africa to continue breeding.[117]

South Africa was chosen as a springboard thanks to its leadership in wildlife management, readily available land, and abundant game. SCT has also been working with the Chinese government to identify suitable sites for the establishment of pilot reserves in China(Dell Latitude 2110 battery). The South China Tigers of the project have since been successfully rewilded and are fully capable of hunting and surviving on their own.[116] This project is also very successful in the breeding of these rewilded South China Tigers and 5 cubs have been born in the project, these cubs of the 2nd generation would be able to learn their survival skills from their successfully rewilded mothers directly. (Dell Latitude E4300 battery)

Success story of rewilding

A rewilded South China Tiger of the Save China's Tigers rewilding project hunting blesbuck

Save China's Tigers' South China Tiger rewilding and reintroduction project has been deemed a success. Recently, renown scientists have confirmed the role of Rewilding captive populations to save the South China Tiger. A rewilding workshop conducted in the October 2010(Dell Vostro 1310 battery), in Laohu Valley reserve, South Africa to access the progress of the rewilding and reintroduction program of Save China's Tigers. The experts present includes Dr. Peter Crawshaw of Centro Nacional de Pesquisa e Conservacão de Mamiferos Carnivoros, Cenap/ICMBIO, Dr. Gary Koehler, Dr. Laurie Marker of Cheetah Conservation Fund, Dr. Jim Sanderson of Small Wild Cat Conservation Foundation, Dr. Nobuyuki Yamaguchi of Department of Biological and Environmental Sciences of Qatar University(Dell Vostro 1320 battery), and Dr. David Smith of Minnesota University, Chinese government scientists as well as representatives of Save China's Tigers.

The tigers involved, were born in captive conditions, in concrete cages and their parents are all captive animals who are unable to sustain in the wild. They were sent to South Africa as part of the Save China's Tigers project to rewilding and ensure that they regain the necessary skills needed for a predator to survive in the wild(Dell Vostro 1510 battery).

Results of the workshop confirmed the important role of the South China Tiger Rewilding Project in tiger conservation. ""Having seen the tigers hunting in an open environment at Laohu Valley Reserve, I believe that these rewilded tigers have the skill to hunt in any environment." Dr. David Smith remarked. Furthermore, Save China's Tigers recovered natural habitat both in China and in South Africa during their attempt to reintroduce South China Tigers back into the wild. (Dell Vostro 1520 battery)

The goal is of preparing tigers born in captivity for introduction to wild habitat in China where tigers once lived seems to be very possible in the near future based on the success of the rewilding and reintroduction program.

Relation with humans

Tiger as prey

Main article: Tiger hunting

Tiger hunting on elephant-back, India, 1808.

Stereographic photograph (1903) of a captured man-eating tiger in the Calcutta zoo; the tiger had claimed 200 human victims(Dell Vostro 2510 battery).

The tiger has been one of the Big Five game animals of Asia. Tiger hunting took place on a large scale in the early nineteenth and twentieth centuries, being a recognised and admired sport by the British in colonial India as well as the maharajas and aristocratic class of the erstwhile princely states of pre-independence India. Tiger hunting was done by some hunters on foot(Dell Vostro 2510 battery); others sat up on machans with a goat or buffalo tied out as bait; yet others on elephant-back.[121] In some cases, villagers beating drums were organised to drive the animals into the killing zone. Elaborate instructions were available for the skinning of tigers and there were taxidermists who specialised in the preparation of tiger skins(Dell Vostro 1014 battery).

Man-eating tigers

Main article: Tiger attack

Although humans are not regular prey for tigers, they have killed more people than any other cat, particularly in areas where population growth, logging, and farming have put pressure on tiger habitats. Most man-eating tigers are old and missing teeth, acquiring a taste for humans because of their inability to capture preferred prey. (Dell Inspiron 1410 battery)Almost all tigers that are identified as man-eaters are quickly captured, shot, or poisoned. Unlike man-eating leopards, even established man-eating tigers will seldom enter human settlements, usually remaining at village outskirts.[123] Nevertheless, attacks in human villages do occur.[124] Man-eaters have been a particular problem in India and Bangladesh, especially in Kumaon(Dell Vostro 1014N battery), Garhwal and the Sundarbans mangrove swamps of Bengal, where some healthy tigers have been known to hunt humans. Because of rapid habitat loss due to climate change, tiger attacks have increased in the Sundarbans.

A female tiger Tatiana escaped from her enclosure in the San Francisco Zoo, killing one person and seriously injuring two more before being shot and killed by the police(Dell Vostro 1015 battery). The enclosure had walls that were lower than they were legally required to be, allowing the tiger to climb the wall and escape.

Traditional Asian medicine

See also: Tiger penis

Many people in China have a belief that various tiger parts have medicinal properties, including as pain killers and aphrodisiacs.[126] There is no scientific evidence to support these beliefs. The use of tiger parts in pharmaceutical drugs in China is already banned, and the government has made some offenses in connection with tiger poaching punishable by death(Dell Vostro 1015N battery). Furthermore, all trade in tiger parts is illegal under the Convention on International Trade in Endangered Species of Wild Fauna and Flora and a domestic trade ban has been in place in China since 1993. Still, there are a number of tiger farms in the country specialising in breeding the cats for profit. It is estimated that between 5,000 and 10,000 captive-bred, semi-tame animals live in these farms today(Dell Inspiron 1088 battery).

In captivity

In recent years, captive breeding of tigers in China has accelerated to the point where the captive population of several tiger subspecies exceeds 4,000 animals. Three thousand specimens are reportedly held by 10–20 "significant" facilities, with the remainder scattered among some 200 facilities. This makes China home to the second largest captive tiger population in the world(Dell Inspiron 1088N battery), after the USA, which in 2005 had an estimated 4,692 captive tigers.[130] In a census conducted by the US based Feline Conservation Federation in 2011, 2,884 tigers were documented as residing in 468 American facilities.[131]

Part of the reason for America's large tiger population relates to legislation. Only nineteen states have banned private ownership of tigers, fifteen require only a license, and sixteen states have no regulations at all. (Dell Vostro A840 battery)The success of breeding programmes at American zoos and circuses led to an overabundance of cubs in the 1980s and 1990s, which drove down prices for the animals. The Society for the Prevention of Cruelty to Animals of Texas estimate there are now 500 lions, tigers and other big cats in private ownership just in the Houston, Texas.[verification needed] A private zoo in Zanesville, Ohio owned 18 Bengal tigers(Dell Vostro A860 battery), all of which were shot dead by Ohio authorities after their owner released them, along with many other dangerous animals, before committing suicide on October 18, 2011.

Genetic ancestry of 105 captive tigers from 14 countries and regions was assessed by using Bayesian analysis and diagnostic genetic markers defined by a prior analysis of 134 voucher tigers of significant genetic distinctiveness. Of the 105 captive tigers(Dell Vostro A860N battery), 49 specimen were assigned to one of five subspecies; 52 specimen had admixed subspecies origins.[133]

The Tiger Species Survival Plan devised by the Association of Zoos and Aquariums has condemned the breeding of white tigers on the allegation that they are of mixed ancestry, hybridized with other subspecies and are of unknown lineage. The genes responsible for white colour are represented by 0.001% of the population(Dell Inspiron Mini 1012 battery). The disproportionate growth in numbers of white tigers points to the relentless inbreeding resorted to among homozygous recessive individuals for selectively multiplying the white animals. This progressively increasing process will eventually lead to inbreeding depression and loss of genetic variability. (SONY PCG-5G2L battery)

Cultural depictions

19th century painting of a tiger by Kuniyoshi Utagawa.

The Bengal tiger is the national animal of India and Bangladesh.[8] The Malaysian tiger is the national animal of Malaysia.[135] The Siberian Tiger is the national animal of South Korea.

The tiger replaces the lion as King of the Beasts in cultures of eastern Asia representing royalty, fearlessness and wrath. (SONY PCG-5G3L battery) Its forehead has a marking which resembles the Chinese character 王, which means "king"; consequently, many cartoon depictions of tigers in China and Korea are drawn with 王 on their forehead.

Of great importance in Chinese myth and culture, the tiger is one of the 12 Chinese zodiac animals. Also in various Chinese art and martial art, the tiger is depicted as an earth symbol and equal rival of the Chinese dragon - the two representing matter and spirit respectively(SONY PCG-F305 battery). In fact, the Southern Chinese martial art Hung Ga is based on the movements of the Tiger and the Crane. In Imperial China, a tiger was the personification of war and often represented the highest army general (or present day defense secretary),[136] while the emperor and empress were represented by a dragon and phoenix, respectively. The White Tiger (Chinese: 白虎; pinyin: Bái Hǔ) is one of the Four Symbols of the Chinese constellations. It is sometimes called the White Tiger of the West (西方白虎), and it represents the west and the autumn season. (SONY PCG-5J1L battery)

In Buddhism, it is also one of the Three Senseless Creatures, symbolising anger, with the monkey representing greed and the deer lovesickness.

Goddess Durga riding a tiger

The Tungusic people considered the Siberian tiger a near-deity and often referred to it as "Grandfather" or "Old man". The Udege and Nanai called it "Amba". The Manchu considered the Siberian tiger as Hu Lin, the king(SONY PCG-5J2L battery).

The widely worshiped Hindu goddess Durga, an aspect of Devi-Parvati, is a ten-armed warrior who rides the tigress (or lioness) Damon into battle. In southern India the god Ayyappan was associated with a tiger.[137]

The weretiger replaces the werewolf in shapeshifting folklore in Asia;[138] in India they were evil sorcerers while in Indonesia and Malaysia they were somewhat more benign. (SONY PCG-5K2L battery)

The tiger continues to be a subject in literature; both Rudyard Kipling, in The Jungle Book, and William Blake, in Songs of Experience, depict the tiger as a menacing and fearful animal. In The Jungle Book, the tiger, Shere Khan, is the wicked mortal enemy of the protagonist, Mowgli. However, other depictions are more benign(SONY PCG-5L1L battery): Tigger, the tiger from A. A. Milne's Winnie-the-Pooh stories, is cuddly and likable. In the Man Booker Prize winning novel "Life of Pi", the protagonist, Pi Patel, sole human survivor of a ship wreck in the Pacific Ocean, befriends another survivor: a large Bengal Tiger. The famous comic strip Calvin and Hobbes features Calvin and his stuffed tiger, Hobbes(SONY PCG-6S2L battery). A tiger is also featured on the cover of the popular cereal Frosted Flakes (also marketed as "Frosties") bearing the name "Tony the Tiger".

World's favourite animal

In a poll conducted by Animal Planet, the tiger was voted the world's favourite animal, narrowly beating the dog. More than 50,000 viewers from 73 countries voted in the poll. Tigers received 21% of the vote, dogs 20%, dolphins 13%, horses 10%, lions 9%, snakes 8%, followed by elephants, chimpanzees, orangutans and whales(SONY PCG-6S3L battery).

Animal behaviourist Candy d'Sa, who worked with Animal Planet on the list, said: "We can relate to the tiger, as it is fierce and commanding on the outside, but noble and discerning on the inside".[140]

Callum Rankine, international species officer at the World Wildlife Federation conservation charity, said the result gave him hope. "If people are voting tigers as their favourite animal, it means they recognise their importance, and hopefully the need to ensure their survival," he said(SONY PCG-6V1L battery).

The lion (Panthera leo) is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg (550 lb) in weight,[4] it is the second-largest living cat after the tiger. Wild lions currently exist in sub-Saharan Africa and in Asia, with an endangered remnant population in Gir Forest National Park in India(Dell 1691P battery), having disappeared from North Africa and Southwest Asia in historic times. Until the late Pleistocene, about 10,000 years ago, the lion was the most widespread large land mammal after humans. They were found in most of Africa, across Eurasia from western Europe to India, and in the Americas from the Yukon to Peru.[5] The lion is a vulnerable species(Dell 310-6321 battery), having seen a major population decline of 30–50% over the past two decades in its African range.[2] Lion populations are untenable outside designated reserves and national parks. Although the cause of the decline is not fully understood, habitat loss and conflicts with humans are currently the greatest causes of concern. Within Africa, the West African lion population is particularly endangered(Dell 312-0068 battery).

Lions live for 10–14 years in the wild, while in captivity they can live longer than 20 years. In the wild, males seldom live longer than 10 years, as injuries sustained from continual fighting with rival males greatly reduce their longevity.[6] They typically inhabit savanna and grassland, although they may take to bush and forest. Lions are unusually social compared to other cats(Dell 312-0078 battery). A pride of lions consists of related females and offspring and a small number of adult males. Groups of female lions typically hunt together, preying mostly on large ungulates. Lions are apex and keystone predators, although they scavenge as opportunity allows. While lions do not typically hunt humans, some have been known to do so. Sleeping mainly during the day, lions are primarily nocturnal, although bordering on crepuscular[7][8] in nature(Dell 312-0079 battery).

Highly distinctive, the male lion is easily recognised by its mane, and its face is one of the most widely recognised animal symbols in human culture. Depictions have existed from the Upper Paleolithic period, with carvings and paintings from the Lascaux and Chauvet Caves, through virtually all ancient and medieval cultures where they once occurred(Dell 312-0305 battery). It has been extensively depicted in sculptures, in paintings, on national flags, and in contemporary films and literature. Lions have been kept in menageries since the time of the Roman Empire, and have been a key species sought for exhibition in zoos over the world since the late 18th century. Zoos are cooperating worldwide in breeding programs for the endangered Asiatic subspecies(Dell 312-0326 battery).

Etymology

The lion's name, similar in many Romance languages, is derived from the Latin leo;[9] and the Ancient Greek λέων (leon).[10] The Hebrew word לָבִיא (lavi) may also be related.[11] It was one of the many species originally described by Linnaeus, who gave it the name Felis leo, in his 18th-century work, Systema Naturae. (Dell 312-0518 battery)

Taxonomy and evolution

The lion's closest relatives are the other species of the genus Panthera: the tiger, the jaguar, and the leopard. P. leo evolved in Africa between 1 million and 800,000 years ago, before spreading throughout the Holarctic region.[12] It appeared in the fossil record in Europe for the first time 700,000 years ago with the subspecies Panthera leo fossilis at Isernia in Italy(Dell 312-0566 battery). From this lion derived the later cave lion (Panthera leo spelaea), which appeared about 300,000 years ago.[13] Lions died out in northern Eurasia at the end of the last glaciation, about 10,000 years ago;[14] this may have been secondary to the extinction of Pleistocene megafauna.[15]

Subspecies

Traditionally, 12 recent subspecies of lion were recognised, distinguished by mane appearance, size, and distribution(Dell 312-0585 battery). Because these characteristics are very insignificant and show a high individual variability, most of these forms were probably not true subspecies, especially as they were often based upon zoo material of unknown origin that may have had "striking, but abnormal" morphological characteristics.[16] Today, only eight subspecies are usually accepted,[14][17] although one of these(Dell 312-0831 battery), the Cape lion, formerly described as Panthera leo melanochaita, probably is invalid.[17] Even the remaining seven subspecies might be too many. While the status of the Asiatic lion (P. l. persica) as a subspecies is generally accepted, the systematic relationships among African lions are still not completely resolved. Mitochondrial variation in living African lions seemed to be modest according to some newer studies(Dell BAT30WL battery), therefore all sub-Saharan lions sometimes have been considered a single subspecies. However, a recent study revealed lions from western and central Africa differ genetically from lions of southern or eastern Africa. According to this study, Western African lions are more closely related to Asian lions than to South or East African lions(Dell D6400 battery). These findings might be explained by a late Pleistocene extinction event of lions in western and central Africa and a subsequent recolonisation of these parts from Asia.[18] Previous studies, which were focused mainly on lions from eastern and southern parts of Africa, already showed these can be possibly divided in two main clades: one to the west of the Great Rift Valley and the other to the east(Dell HF674 battery). Lions from Tsavo in eastern Kenya are much closer genetically to lions in Transvaal (South Africa), than to those in the Aberdare Range in western Kenya.[19] Another study revealed there are three major types of lions, one North African–Asian, one southern African and one middle African.[20] Conversely, Per Christiansen found that using skull morphology allowed him to identify the subspecies krugeri(Dell N3010 battery), nubica, persica, and senegalensis, while there was overlap between bleyenberghi with senegalensis and krugeri. The Asiatic lion persica was the most distinctive, and the Cape lion had characteristics allying it more with P. l. persica than the other sub-Saharan lions. He had analysed 58 lion skulls in three European museums. (Dell Inspiron N4010 battery)

Recent

Eight recent (Holocene) subspecies are recognised today:

P. l. persica, known as the Asiatic lion or South Asian, Persian, or Indian lion, once was widespread from Turkey, across Southwest Asia, to Pakistan, India, and even to Bangladesh. However, large prides and daylight activity made them easier to poach than tigers or leopards; now around 300 exist in and near the Gir Forest of India. Genetic evidence suggests its ancestors split from the ancestors of sub-Saharan African lions between 203 and 74 thousand years ago. (Dell INSPIRON 1100 battery)

P. l. leo, known as the Barbary lion, originally ranged from Morocco to Egypt. It is extinct in the wild due to excessive hunting, as the last wild Barbary lion was killed in Morocco in 1922.[23] This was one of the largest of the lion subspecies,[24] with reported lengths of 3.0–3.3 m (9.8–10.8 ft) and weights of more than 200 kg (440 lb) for males. It appears to be more closely related to the Asiatic rather than sub-Saharan lions(Dell Inspiron 1200 battery). A number of animals in captivity are likely to be Barbary lions,[25] particularly the 90 animals descended from the Moroccan Royal collection at Rabat Zoo.[26]

P. l. senegalensis, known as the West African lion, is found in western Africa, from Senegal to the Central African Republic.

P. l. azandica, known as the northeast Congo Lion, is found in the northeastern parts of the Congo. (Dell Inspiron 1420 battery)

P. l. nubica, known as the East African or Masai lion is found in East Africa, from Ethiopia and Kenya to Tanzania and Mozambique;[28] a local population is known as the Tsavo lion.

P. l. bleyenberghi, known as the southwest African or Katanga lion, is found in southwestern Africa, Namibia, Botswana, Angola, Katanga (Democratic Republic of the Congo), Zambia, and Zimbabwe. (Dell Inspiron 1464 battery)

P. l. krugeri, known as the southeast African or Transvaal lion, is found in the Transvaal region of southeastern Africa, including Kruger National Park.[28]

P. l. melanochaita, known as the Cape lion, became extinct in the wild around 1860. Results of mitochondrial DNA research do not support its status as a distinct subspecies. The Cape lion probably was only the southernmost population of the extant P. l. krugeri. (Dell Inspiron 1564 battery)

Pleistocene

Several additional subspecies of lion existed in prehistoric times:

P. l. fossilis, known as the Middle Pleistocene European cave lion, flourished about 500,000 years ago; fossils have been recovered from Germany and Italy. It was larger than today's African lions, reaching sizes comparable to the American cave lion and slightly larger than the Upper Pleistocene European cave lion(Dell Inspiron 1764 battery).

Cave lions, Chamber of Felines, Lascaux caves

P. l. spelaea, known as the European cave lion, Eurasian cave lion, or Upper Pleistocene European cave lion, occurred in Eurasia 300,000 to 10,000 years ago.[14] This species is known from Paleolithic cave paintings, ivory carvings, and clay busts,[30] indicating it had protruding ears, tufted tails, perhaps faint tiger-like stripes, and at least some males had a ruff or primitive mane around their necks. (Dell Inspiron 1520 battery)

P. l. atrox, known as the American lion or American cave lion, was abundant in the Americas from Canada to Peru in the Pleistocene Epoch until about 10,000 years ago. This form is the sister clade of P. l. spelaea, and likely arose when an early P. l. spelaea population became isolated south of the North American continental ice sheet about 0.34 Mya. (Dell Inspiron 1521 battery) One of the largest purported lion subspecies to have existed, its body length is estimated to have been 1.6–2.5 m (5–8 ft).[33]

Dubious

P. l. youngi or Panthera youngi, flourished 350,000 years ago.[5] Its relationship to the extant lion subspecies is obscure, and it probably represents a distinct species.

P. l. sinhaleyus, known as the Sri Lanka lion, appears to have become extinct around 39,000 years ago. It is only known from two teeth found in deposits at Kuruwita. Based on these teeth, P. Deraniyagala erected this subspecies in 1939. (Dell inspiron 1525 battery)

P. l. vereshchagini, the Beringian cave lion of Yakutia (Russia), Alaska (USA), and the Yukon Territory (Canada), has been considered a subspecies separate from P. l. spelaea on morphological grounds. However, mitochondrial DNA sequences obtained from cave lion fossils from Europe and Alaska were indistinguishable. (Dell inspiron 1526 battery)

P. l. europaea, known as the European lion, was probably identical with Panthera leo persica or Panthera leo spelea; its status as a subspecies is unconfirmed. It became extinct around 100 AD due to persecution and over-exploitation. It inhabited the Balkans, the Italian Peninsula, southern France, and the Iberian Peninsula. It was a very popular object of hunting among ancient Romans and Greeks(Dell Inspiron 1720 battery).

P. l. maculatus, known as the marozi or spotted lion, sometimes is believed to be a distinct subspecies, but may be an adult lion that has retained its juvenile spotted pattern. If it was a subspecies in its own right, rather than a small number of aberrantly coloured individuals, it has been extinct since 1931. A less likely identity is a natural leopard-lion hybrid commonly known as a leopon. (Dell Inspiron 2000 battery)

Hybrids

Further information: Panthera hybrid, Liger, and Tiglon

Video of lion cubs in the wild, South Africa

Lions have been known to breed with tigers (most often the Siberian and Bengal subspecies) to create hybrids called ligers and tiglons (or tigons).[36] They also have been crossed with leopards to produce leopons,[37] and jaguars to produce jaglions. The marozi is reputedly a spotted lion or a naturally occurring leopon(Dell INSPIRON 2600 battery), while the Congolese spotted lion is a complex lion-jaguar-leopard hybrid called a lijagulep. Such hybrids were once commonly bred in zoos, but this is now discouraged due to the emphasis on conserving species and subspecies. Hybrids are still bred in private menageries and in zoos in China.

The liger is a cross between a male lion and a tigress.[38] Because the growth-inhibiting gene from the female tiger is absent(Dell INSPIRON 3800 battery), a growth-promoting gene is passed on by the male lion, the resulting ligers grow far larger than either parent. They share physical and behavioural qualities of both parent species (spots and stripes on a sandy background). Male ligers are sterile, but female ligers are often fertile. Males have about a 50% chance of having a mane, but if they grow them, their manes will be modest(Dell INSPIRON 4000 battery): around 50% the size of a pure lion mane. Ligers are typically 3.0 to 3.7 m (10 to 12 feet) in length, and can weigh 360 to 450 kg (800 to 1,000 pounds).[38] The less common tiglon or tigon is a cross between a lioness and a male tiger.[39] In contrast to ligers, tigons are often relatively small in comparison to their parents, because of reciprocal gene effects. (Dell Inspiron 5000 battery)

Characteristics

A skeletal mount of an African Lion attacking a Common Eland on display at The Museum of Osteology, Oklahoma City, Oklahoma

The lion is the tallest (at the shoulder) of all living cats, averaging about 14 cm (5.5 in) taller than the tiger. Behind only the tiger, the lion is the second largest living felid in length and weight. Its skull is very similar to that of the tiger, although the frontal region is usually more depressed and flattened(Dell INSPIRON 500M battery), with a slightly shorter postorbital region. The lion's skull has broader nasal openings than the tiger. However, due to the amount of skull variation in the two species, usually, only the structure of the lower jaw can be used as a reliable indicator of species.[41] Lion coloration varies from light buff to yellowish, reddish, or dark ochraceous brown. The underparts are generally lighter and the tail tuft is black(Dell INSPIRON 5100 battery). Lion cubs are born with brown rosettes (spots) on their body, rather like those of a leopard. Although these fade as lions reach adulthood, faint spots often may still be seen on the legs and underparts, particularly on lionesses.

Lions are the only members of the cat family to display obvious sexual dimorphism—that is, males and females look distinctly different. They also have specialised roles that each gender plays in the pride. For instance, the lioness, the hunter, lacks the male's thick mane(Dell INSPIRON 510M battery). The colour of the male's mane varies from blond to black, generally becoming darker as the lion grows older.

During confrontations with others, the mane makes the lion look larger.

Weights for adult lions range between 150–250 kg (330–550 lb) for males and 120–182 kg (264–400 lb) for females.[4] Nowell and Jackson report average weights of 181 kg (400 lb) for males and 126 kg (280 lb) for females.[23] Lions tend to vary in size depending on their environment and area, resulting in a wide spread in recorded weights. For instance(Dell INSPIRON 6000 battery), lions in southern Africa tend to be about 5 percent heavier than those in East Africa, in general.[42]

Head and body length is 170–250 cm (5 ft 7 in – 8 ft 2 in) in males and 140–175 cm (4 ft 7 in – 5 ft 9 in) in females; shoulder height is up to 123 cm (4 ft) in males and as low as 91 cm (3 ft) in females.[43] The tail length is 90–105 cm (2 ft 11 in - 3 ft 5 in) in males and 70–100 cm in females (2 ft 4 in – 3 ft 3 in). (Dell INSPIRON 600M battery)The longest known lion, at nearly 3.6 m (12 ft) in total length, was a black-maned male shot near Mucsso, southern Angola in October 1973; the heaviest lion known in the wild was a man-eater shot in 1936 just outside Hectorspruit in eastern Transvaal, South Africa and weighed 313 kg (690 lb).[44] Another notably outsized male lion, which was shot near Mount Kenya, weighed in at 272 kg (600 lb). (Dell Inspiron 6400 battery) Lions in captivity tend to be larger than lions in the wild—the heaviest lion on record is a male at Colchester Zoo in England named Simba in 1970, which weighed 375 kg (826 lb).[45] However, the frequently cited maximum head and body length of 250 cm (8 ft 2 in) fits rather to extinct Pleistocene forms, like the American lion, with even large modern lions measuring several centimeters less in length(Dell INSPIRON 7000 battery)

The most distinctive characteristic shared by both females and males is that the tail ends in a hairy tuft. In some lions, the tuft conceals a hard "spine" or "spur", approximately 5 mm long, formed of the final sections of tail bone fused together. The lion is the only felid to have a tufted tail—the function of the tuft and spine are unknown. Absent at birth, the tuft develops around 5½ months of age and is readily identifiable at 7 months. (Dell INSPIRON 700M battery)

Mane

The mane of the adult male lion, unique among cats, is one of the most distinctive characteristics of the species. It makes the lion appear larger, providing an excellent intimidation display; this aids the lion during confrontations with other lions and with the species' chief competitor in Africa, the spotted hyena.[48] The presence(Dell Inspiron 710m battery), absence, colour, and size of the mane is associated with genetic precondition, sexual maturity, climate, and testosterone production; the rule of thumb is the darker and fuller the mane, the healthier the lion. Sexual selection of mates by lionesses favors males with the densest, darkest mane.[49] Research in Tanzania also suggests mane length signals fighting success in male–male relationships(Dell INSPIRON 8200 battery). Darker-maned individuals may have longer reproductive lives and higher offspring survival, although they suffer in the hottest months of the year.[50] In prides including a coalition of two or three males, it is possible that lionesses solicit mating more actively with the males who are more heavily maned.[49]

A maneless male lion, who also has little body hair—from Tsavo East National Park, Kenya(Dell INSPIRON 8600 battery)

Scientists once believed that the distinct status of some subspecies could be justified by morphology, including the size of the mane. Morphology was used to identify subspecies such as the Barbary lion and Cape lion. Research has suggested, however, that environmental factors influence the colour and size of a lion's mane(Dell INSPIRON 9100 battery), such as the ambient temperature.[50] The cooler ambient temperature in European and North American zoos, for example, may result in a heavier mane. Thus the mane is not an appropriate marker for identifying subspecies.[17][51] The males of the Asiatic subspecies, however, are characterised by sparser manes than average African lions. (Dell INSPIRON 9200 battery)

In the Pendjari National Park area almost all males are maneless or have very weak manes.[53] Maneless male lions have also been reported from Senegal and from Tsavo East National Park in Kenya, and the original male white lion from Timbavati also was maneless. The testosterone hormone has been linked to mane growth, therefore castrated lions often have minimal to no mane, as the removal of the gonads inhibits testosterone production. (Dell INSPIRON 9300 battery)

Cave paintings of extinct European cave lions exclusively show animals with no mane, or just the hint of a mane, suggesting that they were maneless.[31]

White lions

White lions owe their colouring to a recessive gene; they are rare forms of the subspecies Panthera leo krugeri

The white lion is not a distinct subspecies, but a special morph with a genetic condition, leucism,[16] that causes paler colouration akin to that of the white tiger(Dell Inspiron 9400 battery); the condition is similar to melanism, which causes black panthers. They are not albinos, having normal pigmentation in the eyes and skin. White Transvaal lion (Panthera leo krugeri) individuals occasionally have been encountered in and around Kruger National Park and the adjacent Timbavati Private Game Reserve in eastern South Africa, but are more commonly found in captivity, where breeders deliberately select them(Dell Inspiron E1505 battery). The unusual cream colour of their coats is due to a recessive gene.[55] Reportedly, they have been bred in camps in South Africa for use as trophies to be killed during canned hunts.[56]

Kevin Richardson is an animal behaviourist who works with the native big cats of Africa. He currently works in a special facility called the Kingdom of the White Lion in Broederstroom[57] which is 50 miles form Johannesburg.[58] The site was built with the help of Rodney Fuhr(Dell Inspiron E1705 battery) and was made for the movie set of White Lion: Home is a Journey.[58] He has 39 white lions on-site[57] and works diligently to protect and preserve the white lion type. While the park is currently a private property, there are plans to open it to the public soon.[60]

Behaviour

Lions spend much of their time resting and are inactive for about 20 hours per day.[61] Although lions can be active at any time, their activity generally peaks after dusk with a period of socializing, grooming(Dell Inspiron Mini 9 battery), and defecating. Intermittent bursts of activity follow through the night hours until dawn, when hunting most often takes place. They spend an average of two hours a day walking and 50 minutes eating.[62]

Group organization

Lions are the most socially inclined of all wild felids, most of which remain quite solitary in nature. The lion is a predatory carnivore who manifest two types of social organization. Some are residents, living in groups, called prides. (Dell Latitude D400 battery) The pride usually consists of five or six related females, their cubs of both sexes, and one or two males (known as a coalition if more than one) who mate with the adult females (although extremely large prides, consisting of up to 30 individuals, have been observed). The number of adult males in a coalition is usually two, but may increase to four and decrease again over time. Male cubs are excluded from their maternal pride when they reach maturity(Dell STUDIO 1450 battery).

Two lionesses and a mature male of a pride, northern Serengeti

The second organizational behaviour is labeled nomads, who range widely and move about sporadically, either singularly or in pairs.[63] Pairs are more frequent among related males who have been excluded from their birth pride. Note that a lion may switch lifestyles; nomads may become residents and vice versa. Males have to go through this lifestyle and some never are able to join another pride(Dell Vostro 1400 battery). A female who becomes a nomad has much greater difficulty joining a new pride, as the females in a pride are related, and they reject most attempts by an unrelated female to join their family group.

The area a pride occupies is called a pride area, whereas that by a nomad is a range.[63] The males associated with a pride tend to stay on the fringes, patrolling their territory. Why sociality—the most pronounced in any cat species—has developed in lionesses is the subject of much debate(Dell Vostro 1500 battery). Increased hunting success appears an obvious reason, but this is less than sure upon examination: coordinated hunting does allow for more successful predation, but also ensures that non-hunting members reduce per capita caloric intake, however, some take a role raising cubs, who may be left alone for extended periods of time. Members of the pride regularly tend to play the same role in hunts(Dell XPS GEN 2 battery). The health of the hunters is the primary need for the survival of the pride and they are the first to consume the prey at the site it is taken. Other benefits include possible kin selection (better to share food with a related lion than with a stranger), protection of the young, maintenance of territory, and individual insurance against injury and hunger. (Dell XPS M1210 battery)

Video of a lion in the wild

Lionesses do the majority of the hunting for their pride, being smaller, swifter and more agile than the males, and unencumbered by the heavy and conspicuous mane, which causes overheating during exertion. They act as a co-ordinated group in order to stalk and bring down the prey successfully. However, if nearby the hunt, males have a tendency to dominate the kill once the lionesses have succeeded(Dell XPS M1330 battery). They are more likely to share with the cubs than with the lionesses, but rarely share food they have killed by themselves. Smaller prey is eaten at the location of the hunt, thereby being shared among the hunters; when the kill is larger it often is dragged to the pride area. There is more sharing of larger kills,[64] although pride members often behave aggressively toward each other as each tries to consume as much food as possible(Dell XPS 1340 battery).

Both males and females defend the pride against intruders. Some individual lions consistently lead the defence against intruders, while others lag behind.[65] Lions tend to assume specific roles in the pride. Those lagging behind may provide other valuable services to the group.[66] An alternative hypothesis is that there is some reward associated with being a leader who fends off intruders and the rank of lionesses in the pride is reflected in these responses. (Dell XPS M1530 battery) The male or males associated with the pride must defend their relationship to the pride from outside males who attempt to take over their relationship with the pride. Females form the stable social unit in a pride and do not tolerate outside females;[68] membership only changes with the births and deaths of lionesses,[69] although some females do leave and become nomadic. (Dell XPS M170 battery)Subadult males on the other hand, must leave the pride when they reach maturity at around 2–3 years of age.[70]

Hunting and diet

While a lioness such as this one has very sharp teeth, prey is usually killed by strangulation

Lions are powerful animals that usually hunt in coordinated groups and stalk their chosen prey. However, they are not particularly known for their stamina—for instance, a lioness' heart makes up only 0.57 percent of her body weight (Dell XPS M1710 battery) (a male's is about 0.45 percent of his body weight), whereas a hyena's heart is close to 1 percent of its body weight.[71] Thus, they only run fast in short bursts,[72] and need to be close to their prey before starting the attack. They take advantage of factors that reduce visibility; many kills take place near some form of cover or at night.[73] They sneak up to the victim until they reach a distance of around 30 metres (98 ft) or less(Dell XPS M1730 battery). The lioness is the one who does the hunting for the pride, since the lioness is more aggressive by nature. The male lion usually stays and watches its young while waiting for the lionesses to return from the hunt. Typically, several lionesses work together and encircle the herd from different points. Once they have closed with a herd, they usually target the closest prey(Dell XPS M2010 battery). The attack is short and powerful; they attempt to catch the victim with a fast rush and final leap. The prey usually is killed by strangulation,[74] which can cause cerebral ischemia or asphyxia (which results in hypoxemic, or "general", hypoxia). The prey also may be killed by the lion enclosing the animal's mouth and nostrils in its jaws[75] (which would also result in asphyxia). Smaller prey, though, may simply be killed by a swipe of a lion's paw. (Dell Latitude E5400 battery)

Lioness in a burst of speed while hunting in the Serengeti

The prey consists mainly of large mammals, with a preference for wildebeest, impalas, zebras, buffalo, and warthogs in Africa and nilgai, wild boar, and several deer species in India. Many other species are hunted, based on availability. Mainly this will include ungulates weighing between 50 and 300 kg (110–660 lb) such as kudu, hartebeest, gemsbok, and eland. (Dell Latitude E5500 battery) Occasionally, they take relatively small species such as Thomson's gazelle or springbok. Lions hunting in groups are capable of taking down most animals, even healthy adults, but in most parts of their range they rarely attack very large prey such as fully grown male giraffes due to the danger of injury(Dell Latitude E6400 battery).

Extensive statistics collected over various studies show that lions normally feed on mammals in the range 190–550 kg (420–1210 lb). In Africa, wildebeest rank at the top of preferred prey (making nearly half of the lion prey in the Serengeti) followed by zebra.[76] Most adult hippopotamuses, rhinoceroses, elephants, and smaller gazelles, impala(Dell Latitude E6500 battery), and other agile antelopes are generally excluded. However giraffes and buffalos are often taken in certain regions. For instance, in Kruger National Park, giraffes are regularly hunted.[77] In Manyara Park, Cape buffaloes constitute as much as 62% of the lion's diet,[78] due to the high number density of buffaloes. Occasionally hippopotamus is also taken, but adult rhinoceroses are generally avoided(Dell Inspiron Mini 12 battery). Even though smaller than 190 kg (420 lb), warthogs are often taken depending on availability.[79] In some areas, lions specialise in hunting atypical prey species; this is the case at the Savuti river, where they prey on elephants.[80] Park guides in the area reported that the lions, driven by extreme hunger, started taking down baby elephants, and then moved on to adolescents and(Dell XPS M140 battery), occasionally, fully grown adults during the night when elephants' vision is poor.[81] Lions also attack domestic livestock; in India cattle contribute significantly to their diet.[52] Lions are capable of killing other predators such as leopards, cheetahs, hyenas, and wild dogs, though (unlike most felids) they seldom devour the competitors after killing them(Dell XPS 13 battery). They also scavenge animals either dead from natural causes (disease) or killed by other predators, and keep a constant lookout for circling vultures, being keenly aware that they indicate an animal dead or in distress.[82] A lion may gorge itself and eat up to 30 kg (66 lb) in one sitting;[83] if it is unable to consume all the kill it will rest for a few hours before consuming more(Dell XPS 16 battery). On a hot day, the pride may retreat to shade leaving a male or two to stand guard.[84] An adult lioness requires an average of about 5 kg (11 lb) of meat per day, a male about 7 kg (15.5 lb).

Four lions take down a cape buffalo in the central Serengeti, Tanzania

Because lionesses hunt in open spaces where they are easily seen by their prey, cooperative hunting increases the likelihood of a successful hunt; this is especially true with larger species. Teamwork also enables them to defend their kills more easily against other large predators such as hyenas(Dell XPS 1640 battery), which may be attracted by vultures from kilometres away in open savannas. Lionesses do most of the hunting; males attached to prides do not usually participate in hunting, except in the case of larger quarry such as giraffe and buffalo. In typical hunts, each lioness has a favored position in the group, either stalking prey on the "wing" then attacking(Dell XPS 1645 battery), or moving a smaller distance in the centre of the group and capturing prey in flight from other lionesses.[86] Young lions first display stalking behaviour around three months of age, although they do not participate in hunting until they are almost a year old. They begin to hunt effectively when nearing the age of two(Dell XPS 1647 battery).

Predator competition

Subadult male lion and spotted hyena in the Masai Mara

Lions and spotted hyenas occupy the same ecological niche (and hence compete) where they coexist. A review of data across several studies indicates a dietary overlap of 58.6%.[88] Lions typically ignore spotted hyenas, unless they are on a kill or are being harassed by them, while the latter tend to visibly react to the presence of lions, whether there is food or not(Dell Latitude 131L battery). Lions seize the kills of spotted hyenas: in the Ngorongoro crater, it is common for lions to subsist largely on kills stolen from hyenas, causing the hyenas to increase their kill rate. Lions are quick to follow the calls of hyenas feeding, a fact which was proven by Dr. Hans Kruuk, who found that lions repeatedly approached him whenever he played the tape-recorded calls of hyenas feeding. (Dell Latitude C400 battery) When confronted on a kill by lions, spotted hyenas will either leave or wait patiently at a distance of 30–100 m (100–350 ft) until the lions have finished.[90] In some cases, spotted hyenas are bold enough to feed alongside lions, and may occasionally force the lions off a kill. The two species may act aggressively toward one another even when there is no food involved(Dell Latitude C500 battery). Lions may charge at hyenas and maul them for no apparent reason: one male lion was filmed killing two matriarch hyenas on separate occasions without eating them,[91] and lion predation can account for up to 71% of hyena deaths in Etosha. Spotted hyenas have adapted by frequently mobbing lions which enter their territories. (Dell Latitude C510 battery) Experiments on captive spotted hyenas revealed that specimens with no prior experience with lions act indifferently to the sight of them, but will react fearfully to the scent.[89]

Lions tend to dominate smaller felines such as cheetahs and leopards where they co-occur, stealing their kills and killing their cubs and even adults when given the chance. The cheetah has a 50% chance of losing its kill to lions or other predators. (Dell Latitude C540 battery) Lions are major killers of cheetah cubs, up to 90% of which are lost in their first weeks of life due to attacks by other predators. Cheetahs avoid competition by hunting at different times of the day and hide their cubs in thick brush. Leopards also use such tactics, but have the advantage of being able to subsist much better on small prey than either lions or cheetahs(Dell Latitude C600 battery). Also, unlike cheetahs, leopards can climb trees and use them to keep their cubs and kills away from lions. However, lionesses will occasionally be successful in climbing to retrieve leopard kills.[94] Similarly, lions dominate African wild dogs, not only taking their kills but also preying on young and (rarely) adult dogs. Population densities of wild dogs are low in areas where lions are more abundant. (Dell Latitude C610 battery) However, in Kruger National Park, there have been records of wild dogs killing lions and there is one report of eight dogs killing and eating an adult male.[96]

The Nile crocodile is the only sympatric predator (besides humans) that can singly threaten the lion. Depending on the size of the crocodile and the lion, either can lose kills or carrion to the other. Lions have been known to kill crocodiles venturing onto land,[97] while the reverse is true for lions entering waterways, as evidenced by the occasional lion claw found in crocodile stomachs. (Dell Latitude C640 battery)

Reproduction and life cycle

Most lionesses will have reproduced by the time they are four years of age.[99] Lions do not mate at any specific time of year, and the females are polyestrous.[100] As with other cats, the male lion's penis has spines which point backwards. Upon withdrawal of the penis, the spines rake the walls of the female's vagina, which may cause ovulation. (Dell Latitude C800 battery) A lioness may mate with more than one male when she is in heat;[102] during a mating bout, which could last several days, the couple copulates twenty to forty times a day and are likely to forgo eating. Lions reproduce very well in captivity.

Lions mating in Ngorongoro Conservation Area, Tanzania

The average gestation period is around 110 days,[100] the female giving birth to a litter of one to four cubs in a secluded den (which may be a thicket(Dell Latitude C810 battery), a reed-bed, a cave or some other sheltered area) usually away from the rest of the pride. She will often hunt by herself while the cubs are still helpless, staying relatively close to the thicket or den where the cubs are kept.[103] The cubs themselves are born blind—their eyes do not open until roughly a week after birth. They weigh 1.2–2.1 kg (2.6–4.6 lb) at birth and are almost helpless, beginning to crawl a day or two after birth and walking around three weeks of age. (Dell Latitude C840 battery) The lioness moves her cubs to a new den site several times a month, carrying them one by one by the nape of the neck, to prevent scent from building up at a single den site and thus avoiding the attention of predators that may harm the cubs.

Usually, the mother does not integrate herself and her cubs back into the pride until the cubs are six to eight weeks old. (Dell Latitude CPI battery) However, sometimes this introduction to pride life occurs earlier, particularly if other lionesses have given birth at about the same time. For instance, lionesses in a pride often synchronise their reproductive cycles so that they cooperate in the raising and suckling of the young (once the cubs are past the initial stage of isolation with their mother) (Dell Latitude CPX battery), who suckle indiscriminately from any or all of the nursing females in the pride. In addition to greater protection, the synchronization of births also has an advantage in that the cubs end up being roughly the same size, and thus have an equal chance of survival. If one lioness gives birth to a litter of cubs a couple of months after another lioness, for instance, then the younger cubs(Dell Latitude D410 battery), being much smaller than their older brethren, are usually dominated by larger cubs at mealtimes—consequently, death by starvation is more common amongst the younger cubs.

A pregnant lioness (right)

In addition to starvation, cubs also face many other dangers, such as predation by jackals, hyenas, leopards, martial eagles and snakes. Even buffaloes, should they catch the scent of lion cubs, often stampede towards the thicket or den where they are being kept(Dell Latitude D420 battery), doing their best to trample the cubs to death while warding off the lioness. Furthermore, when one or more new males oust the previous male(s) associated with a pride, the conqueror(s) often kill any existing young cubs,[106] perhaps because females do not become fertile and receptive until their cubs mature or die. All in all, as many as 80 percent of the cubs will die before the age of two. (Dell Latitude D430 battery)

When first introduced to the rest of the pride, the cubs initially lack confidence when confronted with adult lions other than their mother. However, they soon begin to immerse themselves in the pride life, playing amongst themselves or attempting to initiate play with the adults. Lionesses with cubs of their own are more likely to be tolerant of another lioness's cubs than lionesses without cubs(Dell Latitude D500 battery). The tolerance of the male lions towards the cubs varies—sometimes, a male will patiently let the cubs play with his tail or his mane, whereas another may snarl and bat the cubs away.

The tolerance of male lions towards the cubs varies. They are, however, generally more likely to share food with the cubs than with the lionesses.

Weaning occurs after six to seven months. Male lions reach maturity at about 3 years of age and, at 4–5 years of age, are capable of challenging and displacing the adult male(s) associated with another pride(Dell Latitude D505 battery). They begin to age and weaken between 10 and 15 years of age at the latest,[109] if they have not already been critically injured while defending the pride (once ousted from a pride by rival males, male lions rarely manage a second take-over). This leaves a short window for their own offspring to be born and mature. If they are able to procreate as soon as they take over a pride(Dell Latitude D510 battery), potentially, they may have more offspring reaching maturity before they also are displaced. A lioness often will attempt to defend her cubs fiercely from a usurping male, but such actions are rarely successful. He usually kills all of the existing cubs who are less than two years old. A lioness is weaker and much lighter than a male; success is more likely when a group of three or four mothers within a pride join forces against one male. (Dell Latitude D520 battery)

Contrary to popular belief, it is not only males that are ousted from their pride to become nomads, although most females certainly do remain with their birth pride. However, when the pride becomes too large, the next generation of female cubs may be forced to leave to eke out their own territory. Furthermore, when a new male lion takes over the pride(Dell Latitude D600 battery), subadult lions, both male and female, may be evicted.[110] Life is harsh for a female nomad. Nomadic lionesses rarely manage to raise their cubs to maturity, without the protection of other pride members. One scientific study reports that both males and females may interact homosexually.

Health

Although adult lions have no natural predators, evidence suggests that the majority die violently from humans or other lions. (Dell Latitude D610 battery) Lions often inflict serious injuries on each other, either members of different prides encountering each other in territorial disputes, or members of the same pride fighting at a kill.[114] Crippled lions and lion cubs may fall victim to hyenas, leopards, or be trampled by buffalo or elephants, and careless lions may be maimed when hunting prey(Dell Latitude D620 battery).

One of the tree climbing Lions of the Serengeti, Tanzania

Various species of tick commonly infest the ears, neck and groin regions of most lions. Adult forms of several species of the tapeworm genus Taenia have been isolated from intestines, the lions having ingested larval forms from antelope meat.[118] Lions in the Ngorongoro Crater were afflicted by an outbreak of stable fly (Stomoxys calcitrans) in 1962(Dell Latitude D630 battery); this resulted in lions becoming covered in bloody bare patches and emaciated. Lions sought unsuccessfully to evade the biting flies by climbing trees or crawling into hyena burrows; many perished or emigrated as the population dropped from 70 to 15 individuals.[119] A more recent outbreak in 2001 killed six lions.[120] Lions, especially in captivity, are vulnerable to the canine distemper virus (CDV), feline immunodeficiency virus (FIV) (Dell Latitude D800 battery), and feline infectious peritonitis (FIP).[16] CDV is spread through domestic dogs and other carnivores; a 1994 outbreak in Serengeti National Park resulted in many lions developing neurological symptoms such as seizures. During the outbreak, several lions died from pneumonia and encephalitis.[121] FIV, which is similar to HIV while not known to adversely affect lions(Dell Latitude D810 battery), is worrisome enough in its effect in domestic cats that the Species Survival Plan recommends systematic testing in captive lions. It occurs with high to endemic frequency in several wild lion populations, but is mostly absent from Asiatic and Namibian lions.[16]

Communication

Head rubbing and licking are common social behaviours within a pride

When resting, lion socialization occurs through a number of behaviours, and the animal's expressive movements are highly developed. The most common peaceful tactile gestures are head rubbing and social licking, (Dell Latitude D820 battery) which have been compared with grooming in primates. Head rubbing—nuzzling one's forehead, face and neck against another lion—appears to be a form of greeting,[124] as it is seen often after an animal has been apart from others, or after a fight or confrontation. Males tend to rub other males, while cubs and females rub females. Social licking often occurs in tandem with head rubbing(Dell Latitude D830 battery); it is generally mutual and the recipient appears to express pleasure. The head and neck are the most common parts of the body licked, which may have arisen out of utility, as a lion cannot lick these areas individually.[126]

Lions have an array of facial expressions and body postures that serve as visual gestures.[127] Their repertoire of vocalizations is also large; variations in intensity and pitch, rather than discrete signals, appear central to communication(Dell Latitude 2100 battery). Lion sounds include snarling, purring, hissing, coughing, miaowing, woofing and roaring. Lions tend to roar in a very characteristic manner, starting with a few deep, long roars that trail off into a series of shorter ones. They most often roar at night; the sound, which can be heard from a distance of 8 kilometres (5.0 mi), is used to advertise the animal's presence.[128] Lions have the loudest roar of any big cat(Dell Latitude 2110 battery).

Distribution and habitat

Two male Asiatic lions in Sanjay Gandhi National Park, Mumbai, India. The wild population of the endangered Asiatic lions is restricted to the Gir Forest National Park in western India.[129]

In Africa, lions can be found in savanna grasslands with scattered Acacia trees which serve as shade;[130] their habitat in India is a mixture of dry savanna forest and very dry deciduous scrub forest. (Dell Latitude E4300 battery) The habitat of lions originally spanned the southern parts of Eurasia, ranging from Greece to India, and most of Africa except the central rainforest-zone and the Sahara desert. Herodotus reported that lions had been common in Greece around 480 BC; they attacked the baggage camels of the Persian king Xerxes on his march through the country. Aristotle considered them rare by 300 BC. By 100 AD they were extirpated. (Dell Vostro 1310 battery) A population of Asiatic lions survived until the tenth century in the Caucasus, their last European outpost.

The species was eradicated from Palestine by the Middle Ages and from most of the rest of Asia after the arrival of readily available firearms in the eighteenth century. Between the late nineteenth and early twentieth century they became extinct in North Africa and Southwest Asia(Dell Vostro 1320 battery). By the late nineteenth century the lion had disappeared from Turkey and most of northern India,[16][134] while the last sighting of a live Asiatic lion in Iran was in 1941 (between Shiraz and Jahrom, Fars Province), although the corpse of a lioness was found on the banks of the Karun river, Khūzestān Province in 1944. There are no subsequent reliable reports from Iran. (Dell Vostro 1510 battery) The subspecies now survives only in and around the Gir Forest of northwestern India.[22] About 300 lions live in a 1,412 km2 (545 sq mi) sanctuary in the state of Gujarat, which covers most of the forest. Their numbers are slowly increasing.[135]

Population and conservation status

Main article: Lion hunting

The Asiatic lion, whose habitat once ranged from the Mediterranean to north-west Indian subcontinent, is today found only in the Gir Forest of Gujarat, India. Only about 320 Asiatic lions survive in the wild. (Dell Vostro 1520 battery)

Most lions now live in eastern and southern Africa, and their numbers there are rapidly decreasing, with an estimated 30–50% decline over the last two decades.[2] Estimates of the African lion population range between 16,500 and 47,000 living in the wild in 2002–2004, down from early 1990s estimates that ranged as high as 100,000 and perhaps 400,000 in 1950(Dell Vostro 2510 battery). Primary causes of the decline include disease and human interference.[2] Habitat loss and conflicts with humans are considered the most significant threats to the species.[139][140] The remaining populations are often geographically isolated from one another, which can lead to inbreeding, and consequently, reduced genetic diversity. Therefore the lion is considered a vulnerable species by the International Union for Conservation of Nature, while the Asiatic subspecies is endangered. (Dell Vostro 1014 battery) The lion population in the region of West Africa is isolated from lion populations of Central Africa, with little or no exchange of breeding individuals. The number of mature individuals in West Africa is estimated by two separate recent surveys at 850–1,160 (2002/2004). There is disagreement over the size of the largest individual population in West Africa(Dell Inspiron 1410 battery): the estimates range from 100 to 400 lions in Burkina Faso's Arly-Singou ecosystem.[2] Another population in northwestern Africa is found in Waza National Park, where only about 14-21 animals persist

Conservation of both African and Asian lions has required the setup and maintenance of national parks and game reserves(Dell Vostro 1014N battery); among the best known are Etosha National Park in Namibia, Serengeti National Park in Tanzania, and Kruger National Park in eastern South Africa. Outside these areas, the issues arising from lions' interaction with livestock and people usually results in the elimination of the former.[143] In India, the last refuge of the Asiatic lion is the 1,412 km2 (545 sq mi) Gir Forest National Park in western India which had about 359 lions (as of April 2006) (Dell Vostro 1015 battery). As in Africa, numerous human habitations are close by with the resultant problems between lions, livestock, locals and wildlife officials.[144] The Asiatic Lion Reintroduction Project plans to establish a second independent population of Asiatic lions at the Kuno Wildlife Sanctuary in the Indian state of Madhya Pradesh(Dell Vostro 1015N battery). It is important to start a second population to serve as a gene pool for the last surviving Asiatic lions and to help develop and maintain genetic diversity enabling the species to survive.

The former popularity of the Barbary lion as a zoo animal has meant that scattered lions in captivity are likely to be descended from Barbary lion stock. This includes twelve lions at Port Lympne Wild Animal Park in Kent, England that are descended from animals owned by the King of Morocco. (Dell Inspiron 1088 battery) Another eleven animals believed to be Barbary lions were found in Addis Ababa zoo, descendants of animals owned by Emperor Haile Selassie. WildLink International, in collaboration with Oxford University, launched their ambitious International Barbary Lion Project with the aim of identifying and breeding Barbary lions in captivity for eventual reintroduction into a national park in the Atlas Mountains of Morocco. (Dell Vostro A840 battery)

Following the discovery of the decline of lion population in Africa, several coordinated efforts involving lion conservation have been organised in an attempt to stem this decline. Lions are one species included in the Species Survival Plan, a coordinated attempt by the Association of Zoos and Aquariums to increase its chances of survival(Dell Vostro A860 battery). The plan was originally started in 1982 for the Asiatic lion, but was suspended when it was found that most Asiatic lions in North American zoos were not genetically pure, having been hybridised with African lions. The African lion plan started in 1993, focusing especially on the South African subspecies, although there are difficulties in assessing the genetic diversity of captive lions(Dell Inspiron Mini 1012 battery), since most individuals are of unknown origin, making maintenance of genetic diversity a problem.[16]

Man-eaters

Main article: Man-eater

While lions do not usually hunt people, some (usually males) seem to seek out human prey; well-publicised cases include the Tsavo maneaters, where 28 railway workers building the Kenya-Uganda Railway were taken by lions over nine months during the construction of a bridge over the Tsavo River in Kenya in 1898, and the 1991 Mfuwe man-eater(SONY PCG-5G2L battery), which killed six people in the Laungwa River Valley in Zambia.[148] In both, the hunters who killed the lions wrote books detailing the animals' predatory behaviour. The Mfuwe and Tsavo incidents bear similarities: the lions in both incidents were larger than normal, lacked manes, and seemed to suffer from tooth decay. The infirmity theory, including tooth decay, is not favored by all researchers(SONY PCG-5G3L battery); an analysis of teeth and jaws of man-eating lions in museum collections suggests that, while tooth decay may explain some incidents, prey depletion in human-dominated areas is a more likely cause of lion predation on humans.

In their analysis of Tsavo and man-eating generally, Kerbis Peterhans and Gnoske acknowledge that sick or injured animals may be more prone to man-eating, but that the behaviour is "not unusual, nor necessarily 'aberrant'" where the opportunity exists(SONY PCG-F305 battery); if inducements such as access to livestock or human corpses are present, lions will regularly prey upon human beings. The authors note that the relationship is well-attested amongst other pantherines and primates in the paleontological record.[150]

The lion's proclivity for man-eating has been systematically examined. American and Tanzanian scientists report that man-eating behaviour in rural areas of Tanzania increased greatly from 1990 to 2005(SONY PCG-5J1L battery). At least 563 villagers were attacked and many eaten over this period—a number far exceeding the more famed "Tsavo" incidents of a century earlier. The incidents occurred near Selous National Park in Rufiji District and in Lindi Province near the Mozambican border. While the expansion of villagers into bush country is one concern, the authors argue that conservation policy must mitigate the danger because, in this case, conservation contributes directly to human deaths(SONY PCG-5J2L battery). Cases in Lindi have been documented where lions seize humans from the center of substantial villages.[151] Another study of 1,000 people attacked by lions in southern Tanzania between 1988 and 2009 found that the weeks following the full moon (when there was less moonlight) were a strong indicator of increased night attacks on people. (SONY PCG-5K2L battery)

The Tsavo Man-Eaters on display in the Field Museum of Natural History in Chicago, Illinois.

Author Robert R. Frump wrote in The Man-eaters of Eden that Mozambican refugees regularly crossing Kruger National Park at night in South Africa are attacked and eaten by the lions; park officials have conceded that man-eating is a problem there. Frump believes thousands may have been killed in the decades after apartheid sealed the park and forced the refugees to cross the park at night(SONY PCG-5L1L battery). For nearly a century before the border was sealed, Mozambicans had regularly walked across the park in daytime with little harm.[153]

Packer estimates more than 200 Tanzanians are killed each year by lions, crocodiles, elephants, hippos, and snakes, and that the numbers could be double that amount, with lions thought to kill at least 70 of those. Packer has documented that between 1990 and 2004(SONY PCG-6S2L battery), lions attacked 815 people in Tanzania, killing 563. Packer and Ikanda are among the few conservationists who believe western conservation efforts must take account of these matters not just because of ethical concerns about human life, but also for the long term success of conservation efforts and lion preservation.[151]

A man-eating lion was killed by game scouts in Southern Tanzania in April 2004(SONY PCG-6S3L battery). It is believed to have killed and eaten at least 35 people in a series of incidents covering several villages in the Rufiji Delta coastal region.[154] Dr Rolf D. Baldus, the GTZ wildlife programme coordinator, commented that it was likely that the lion preyed on humans because it had a large abscess underneath a molar which was cracked in several places. He further commented that "This lion probably experienced a lot of pain, particularly when it was chewing." (SONY PCG-6V1L battery) GTZ is the German development cooperation agency and has been working with the Tanzanian government on wildlife conservation for nearly two decades. As in other cases this lion was large, lacked a mane, and had a tooth problem.

The "All-Africa" record of man-eating generally is considered to be not Tsavo, but incidents in the late 1930s through the late 1940s in what was then Tanganyika (now Tanzania) (SONY PCG-6W1L battery). George Rushby, game warden and professional hunter, eventually dispatched the pride, which over three generations is thought to have killed and eaten 1,500 to 2,000 people in what is now Njombe district.

In captivity

Lions are part of a group of exotic animals that are the core of zoo exhibits since the late eighteenth century; members of this group are invariably large vertebrates and include elephants, rhinoceroses, hippopotamuses, large primates, and other big cats; zoos sought to gather as many of these species as possible. (SONY PCG-7111L battery) Although many modern zoos are more selective about their exhibits,[158] there are over 1,000 African and 100 Asiatic lions in zoos and wildlife parks around the world. They are considered an ambassador species and are kept for tourism, education and conservation purposes.[159] Lions can reach an age of over 20 years in captivity; Apollo, a resident lion of Honolulu Zoo in Honolulu, Hawaii(SONY PCG-71511M battery), died at age 22 in August 2007. His two sisters, born in 1986, are still living (as of August, 2007).[160] Breeding programs need to note origins to avoid breeding different subspecies and thus reducing conservation value.[161]

Male African lion of the Transvaal subspecies (P. l. krugeri)

Lions were kept and bred by Assyrian kings as early as 850 BC,[132] and Alexander the Great was said to have been presented with tame lions by the Malhi of northern India.[162] Later in Roman times, lions were kept by emperors to take part in the gladiator arenas(SONY PCG-6W3L battery). Roman notables, including Sulla, Pompey, and Julius Caesar, often ordered the mass slaughter of hundreds of lions at a time.[163] In the East, lions were tamed by Indian princes, and Marco Polo reported that Kublai Khan kept lions inside.[164] The first European "zoos" spread amongst noble and royal families in the thirteenth century, and until the seventeenth century were called seraglios(SONY PCG-7113L battery); at that time, they came to be called menageries, an extension of the cabinet of curiosities. They spread from France and Italy during the Renaissance to the rest of Europe.[165] In England, although the seraglio tradition was less developed, Lions were kept at the Tower of London in a seraglio established by King John in the thirteenth century, (SONY PCG-7133L battery) probably stocked with animals from an earlier menagerie started in 1125 by Henry I at his palace in Woodstock, near Oxford; where lions had been reported stocked by William of Malmesbury.[168]

Seraglios served as expressions of the nobility's power and wealth. Animals such as big cats and elephants, in particular, symbolised power, and would be pitted in fights against each other or domesticated animals(SONY PCG-7Z1L battery). By extension, menageries and seraglios served as demonstrations of the dominance of humanity over nature. Consequently, the defeat of such natural "lords" by a cow in 1682 astonished the spectators, and the flight of an elephant before a rhinoceros drew jeers. Such fights would slowly fade out in the seventeenth century with the spread of the menagerie and their appropriation by the commoners(SONY PCG-7Z2L battery)       . The tradition of keeping big cats as pets would last into the nineteenth century, at which time it was seen as highly eccentric.[169]

Albrecht Dürer, Lions sketch. Circa 1520

The presence of lions at the Tower of London was intermittent, being restocked when a monarch or his consort, such as Margaret of Anjou the wife of Henry VI, either sought or were given animals. Records indicate they were kept in poor conditions there in the seventeenth century, in contrast to more open conditions in Florence at the time. (SONY PCG-8Y1L battery) The menagerie was open to the public by the eighteenth century; admission was a sum of three half-pence or the supply of a cat or dog for feeding to the lions.[171] A rival menagerie at the Exeter Exchange also exhibited lions until the early nineteenth century. The Tower menagerie was closed down by William IV, and animals transferred to the London Zoo which opened its gates to the public on 27 April 1828(SONY PCG-8Y2L battery).

Animal species disappear when they cannot peacefully orbit the center of gravity that is man.

Pierre-Amédée Pichot, 1891

The wild animals trade flourished alongside improved colonial trade of the nineteenth century. Lions were considered fairly common and inexpensive. Although they would barter higher than tigers, they were less costly than larger, or more difficult to transport animals such as the giraffe and hippopotamus, and much less than pandas. Like other animals(SONY PCG-8Z2L battery), lions were seen as little more than a natural, boundless commodity that was mercilessly exploited with terrible losses in capture and transportation. The widely reproduced imagery of the heroic hunter chasing lions would dominate a large part of the century. Explorers and hunters exploited a popular Manichean division of animals into "good" and "evil" to add thrilling value to their adventures(SONY PCG-8Z1L battery), casting themselves as heroic figures. This resulted in big cats, always suspected of being man-eaters, representing "both the fear of nature and the satisfaction of having overcome it."

Lion at Melbourne Zoo enjoying an elevated grassy area with some tree shelter

Lions were kept in cramped and squalid conditions at London Zoo until a larger lion house with roomier cages was built in the 1870s.[179] Further changes took place in the early twentieth century(SONY PCG-7112L battery), when Carl Hagenbeck designed enclosures more closely resembling a natural habitat, with concrete 'rocks', more open space and a moat instead of bars. He designed lion enclosures for both Melbourne Zoo and Sydney's Taronga Zoo, among others, in the early twentieth century. Though his designs were popular, the old bars and cage enclosures prevailed until the 1960s in many zoos. (SONY PCG-6W2L battery) In the later decades of the twentieth century, larger, more natural enclosures and the use of wire mesh or laminated glass instead of lowered dens allowed visitors to come closer than ever to the animals, with some attractions even placing the den on ground higher than visitors, such as the Cat Forest/Lion Overlook of Oklahoma City Zoological Park. (SONY PCG-5K1L battery)Lions are now housed in much larger naturalistic areas; modern recommended guidelines more closely approximate conditions in the wild with closer attention to the lions' needs, highlighting the need for dens in separate areas, elevated positions in both sun and shade where lions can sit and adequate ground cover and drainage as well as sufficient space to roam. (SONY VGP-BPS13 battery)

There have also been instances where a lion was kept by a private individual, such as the lioness Elsa, who was raised by George Adamson and his wife Joy Adamson and came to develop a strong bond with them, particularly the latter. The lioness later achieved fame, her life being documented in a series of books and films(SONY VGP-BPS13Q battery).

Baiting and taming

Main articles: Lion-baiting and Lion taming

Nineteenth century etching of a lion tamer in a cage of lions

Lion-baiting is a blood sport involving the baiting of lions in combat with other animals, usually dogs. Records of it exist in ancient times through until the seventeenth century. It was finally banned in Vienna by 1800 and England in 1825.

Lion taming refers to the practice of taming lions for entertainment, either as part of an established circus or as an individual act, such as Siegfried & Roy(SONY VGP-BPS13A/Q battery). The term is also often used for the taming and display of other big cats such as tigers, leopards, and cougars. The practice was pioneered in the first half of the nineteenth century by Frenchman Henri Martin and American Isaac Van Amburgh who both toured widely, and whose techniques were copied by a number of followers.[183] Van Amburgh performed before Queen Victoria of the United Kingdom in 1838 when he toured Great Britain(SONY VGP-BPS13B/Q battery). Martin composed a pantomime titled Les Lions de Mysore ("the lions of Mysore"), an idea that Amburgh quickly borrowed. These acts eclipsed equestrianism acts as the central display of circus shows, but truly entered public consciousness in the early twentieth century with cinema. In demonstrating the superiority of human over animal, lion taming served a purpose similar to animal fights of previous centuries. (SONY VGP-BPS13/B battery) The ultimate proof of a tamer's dominance and control over a lion is demonstrated by placing his head in the lion's mouth. The now iconic lion tamer's chair was possibly first used by American Clyde Beatty (1903–1965).

Cultural depictions

For more details on this topic, see Cultural depictions of lions.

Lion on a decorative panel from Darius I the Great's palace during Persian Empire (550–330 BC).

The Lion Gate of Mycenae (detail)—two lionesses flank the central column, c. 1300 BC(SONY VGP-BPS13B/B battery)

Detail of the Chinese-style gate of Nishi Hongan-ji in Kyoto; Momoyama period; National Treasure

The lion has been an icon for humanity for thousands of years, appearing in cultures across Europe, Asia, and Africa. Despite incidents of attacks on humans, lions have enjoyed a positive depiction in culture as strong but noble. A common depiction is their representation as "king of the jungle" or "king of beasts"(SONY VGP-BPS13A/S battery); hence, the lion has been a popular symbol of royalty and stateliness,[185] as well as a symbol of bravery; it is featured in several fables of the 6th century BC Greek storyteller Aesop.[186]

Representations of lions date back 32,000 years; the lion-headed ivory carving from Vogelherd cave in the Swabian Alb in southwestern Germany has been determined to be about 32,000 years old from the Aurignacian culture. (SONY VGP-BPS21A/B battery) Two lions were depicted mating in the Chamber of Felines in 15,000-year-old Paleolithic cave paintings in the Lascaux caves. Cave lions are also depicted in the Chauvet Cave, discovered in 1994; this has been dated at 32,000 years of age,[30] though it may be of similar or younger age to Lascaux.[187]

Ancient Egypt venerated the lioness (the fierce hunter) as their war deities and among those in the Egyptian pantheon are(SONY VGP-BPS21B battery), Bast, Mafdet, Menhit, Pakhet, Sekhmet, Tefnut, and the Sphinx;[185] The Nemean lion was symbolic in Ancient Greece and Rome, represented as the constellation and zodiac sign Leo, and described in mythology, where its skin was borne by the hero Heracles.[188] The lion was a prominent symbol in ancient Mesopotamia (from Sumer up to Assyrian and Babylonian times) (SONY VGP-BPS21 battery), where it was strongly associated with kingship.[189] The classic Babylonian lion motif, found as a statue, carved or painted on walls, is often referred to as the striding lion of Babylon. It is in Babylon that the biblical Daniel is said to have been delivered from the lion's den.[190]

In the Puranic texts of Hinduism, Narasimha ("man-lion") a half-lion, half-man incarnation or (avatar) of Vishnu(SONY VGP-BPS21/S battery), is worshipped by his devotees and saved the child devotee Prahlada from his father, the evil demon king Hiranyakashipu;[191] Vishnu takes the form of half-man/half-lion, in Narasimha, having a human torso and lower body, but with a lion-like face and claws.[192] Singh is an ancient Indian vedic name meaning "lion" (Asiatic lion), dating back over 2000 years to ancient India(SONY VGP-BPS13AS battery). It was originally only used by Rajputs a Hindu Kshatriya or military caste in India. After the birth of the Khalsa brotherhood in 1699, the Sikhs also adopted the name "Singh" due to the wishes of Guru Gobind Singh. Along with millions of Hindu Rajputs today, it is also used by over 20 million Sikhs worldwide.[193] Found famously on numerous flags and coats of arms all across Asia and Europe(SONY VGP-BPS13S battery), the Asiatic lions also stand firm on the National Emblem of India.[194] Further south on the Indian subcontinent, the Asiatic lion is symbolic for the Sinhalese,[195] Sri Lanka's ethnic majority; the term derived from the Indo-Aryan Sinhala, meaning the "lion people" or "people with lion blood", while a sword wielding lion is the central figure on the national flag of Sri Lanka(SONY VGP-BPS13B/S battery).

The Asiatic lion is a common motif in Chinese art. They were first used in art during the late Spring and Autumn Period (fifth or sixth century BC), and became much more popular during the Han Dynasty (206 BC – AD 220), when imperial guardian lions started to be placed in front of imperial palaces for protection. Because lions have never been native to China(SONY VGP-BPS13B/G battery), early depictions were somewhat unrealistic; after the introduction of Buddhist art to China in the Tang Dynasty (after the sixth century AD), lions were usually depicted without wings, their bodies became thicker and shorter, and their manes became curly.[197] The lion dance is a form of traditional dance in Chinese culture in which performers mimic a lion's movements in a lion costume(SONY VGP-BPS14 battery), often with musical accompaniment from cymbals, drums and gongs. They are performed at Chinese New Year, the August Moon Festival and other celebratory occasions for good luck.[198]

The island nation of Singapore derives its name from the Malay words singa (lion) and pora (city/fortress), which in turn is from the Tamil-Sanskrit சிங்க singa सिंह siṃha and पुर புர pura, which is cognate to the Greek πόλις, pólis. (SONY VGP-BPL14 battery)According to the Malay Annals, this name was given by a fourteenth century Sumatran Malay prince named Sang Nila Utama, who, on alighting the island after a thunderstorm, spotted an auspicious beast on shore which appeared to be a lion.

Museo d'arte antica in the Sforza Castle in Milan, Italy: Italian stained glass with heraldic white lion rampant dated 1674(SONY VGP-BPS14/B battery).

"Lion" was the nickname of several medieval warrior rulers with a reputation for bravery, such as the English King Richard the Lionheart, Henry the Lion (German: Heinrich der Löwe), Duke of Saxony and Robert III of Flanders nicknamed "The Lion of Flanders"—a major Flemish national icon up to the present. Lions are frequently depicted on coats of arms, either as a device on shields themselves, or as supporters(SONY VGP-BPS14/S battery). (The lioness is much more infrequent.) The formal language of heraldry, called blazon, employs French terms to describe the images precisely. Such descriptions specified whether lions or other creatures were "rampant" or "passant", that is whether they were rearing or crouching.[202] The lion is used as a symbol of sporting teams, from national association football teams such as England(SONY VGP-BPS14B battery), Scotland and Singapore to famous clubs such as the Detroit Lions[203] of the NFL, Chelsea[204] and Aston Villa of the English Premier League,[205] (and the Premiership itself) to a host of smaller clubs around the world.

Lions continue to feature in modern literature, from the messianic Aslan in The Lion, the Witch and the Wardrobe and following books from The Chronicles of Narnia series written by C. S. Lewis, (SONY VGP-BPS22 battery) to the comedic Cowardly Lion in The Wonderful Wizard of Oz.[207] The advent of moving pictures saw the continued presence of lion symbolism; one of the most iconic and widely recognised lions is Leo the Lion, which has been the mascot for Metro-Goldwyn-Mayer (MGM) studios since the 1920s.[208] The 1960s saw the appearance of what is possibly the most famous lioness(SONY VGP-BPS22 battery), the Kenyan animal Elsa in the movie Born Free,[209] based on the true-life international bestselling book of the same title.[210] The lion's role as King of the Beasts has been used in cartoons, from the 1950s manga which gave rise to the first Japanese colour TV animation series, Kimba the White Lion, Leonardo Lion of King Leonardo and his Short Subjects, both from the 1960s(SONY VGP-BPS18 battery), up to the 1994 Disney animated feature film The Lion King, which also featured the popular song "The Lion Sleeps Tonight" in its soundtrack. A lion appears on the 50-rand South African banknote.

The domestic dog (Canis lupus familiaris), is a subspecies of the gray wolf (Canis lupus), a member of the Canidae family of the mammilian order Carnivora. The term "domestic dog" is generally used for both domesticated and feral varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept workingSony VAIO PCG-8131M battery, hunting, and companion animal in human history. The word "dog" may also mean the male of a canine species, as opposed to the word "bitch" for the female of the species.

The present lineage of dogs was domesticated from gray wolves about 15,000 years ago.[5] Remains of domesticated dogs have been found in Siberia and Belgium from about 33,000 years ago. None of these early domestication lineages seem to have survived the Last Glacial MaximumSony VAIO PCG-8152M battery. Although mDNA testing suggests a split between dogs and wolves around 100,000 years ago, no specimens prior to 33,000 years ago are clearly morphologically domesticated dog.

Dogs' value to early human hunter-gatherers led to them quickly becoming ubiquitous across world cultures. Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship, and, more recently, aiding handicapped individualsSony VAIO PCG-31311M battery. This impact on human society has given them the nickname "Man's Best Friend" in the Western world. In some cultures, dogs are also source of meat. In 2001, there were estimated to be 400 million dogs in the world.[11]

Most breeds of dogs are at most a few hundred years old, having been artificially selected for particular morphologies and behaviors by people for specific functional roles. Through this selective breeding, the dog has developed into hundreds of varied breedsSony VAIO PCG-31111M battery, and shows more behavioral and morphological variation than any other land mammal.[12] For example, height measured to the withers ranges from 6 inches (150 mm) in the Chihuahua to about 2.5 feet (0.76 m) in the Irish Wolfhound; color varies from white through grays (usually called "blue") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patternsSony VAIO PCG-8112M battery; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth.[13] It is common for most breeds to shed this coat.

Etymology and related terminology

"Dog" is the common use term that refers to members of the subspecies Canis lupus familiaris (canis, "dog"; lupus, "wolf"; familiaris, "of a household" or "domestic"). The term can also be used to refer to a wider range of related species, such as the members of the genus CanisSony VAIO PCG-7186M battery, or "true dogs", including the wolf, coyote, and jackals, or it can refer to the members of the tribe Canini, which would also include the African wild dog, or it can be used to refer to any member of the family Canidae, which would also include the foxes, bush dog, raccoon dog, and others.[14] Some members of the family have "dog" in their common names, such as the raccoon dog and the African wild dogSony VAIO PCG-7171M battery. A few animals have "dog" in their common names but are not canids, such as the prairie dog.

The English word "dog" comes from Middle English dogge, from Old English docga, a "powerful dog breed".[15] The term may derive from Proto-Germanic *dukkōn, represented in Old English finger-docce ("finger-muscle").Sony VAIO PCG-9Z1M batteryThe word also shows the familiar petname diminutive -ga also seen in frogga "frog", picga "pig", stagga "stag", wicga "beetle, worm", among others.[17] Due to the archaic structure of the word, the term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary, reflecting the role of the dog as the earliest domesticated animal. Sony VAIO PCG-5S1M battery

In 14th-century England, "hound" (from Old English: hund) was the general word for all domestic canines, and "dog" referred to a subtype of hound, a group including the mastiff. It is believed this "dog" type of "hound" was so common, it eventually became the prototype of the category “hound”.[19] By the 16th century, dog had become the general wordSony VAIO PCG-5P1M battery, and hound had begun to refer only to types used for hunting.[20] Hound, cognate to German Hund, Dutch hond, common Scandinavian hund, and Icelandic hundur, is ultimately derived from the Proto-Indo-European *kwon- "dog", found in Welsh ci (plural cwn), Latin canis, Greek kýōn, and Lithuanian šuõ.[21]

In breeding circles, a male canine is referred to as a dog, while a female is called a bitch (Middle English biccheSony VAIO PCG-5N2M battery, from Old English bicce, ultimately from Old Norse bikkja). A group of offspring is a litter. The father of a litter is called the sire, and the mother is called the dam. Offspring are, in general, called pups or puppies, from French poupée, until they are about a year old. The process of birth is whelping, from the Old English word hwelp (cf. German Welpe, Dutch welp, Swedish valpa, Icelandic hvelpur) Sony VAIO PCG-3C2M battery.

Taxonomy

In 1753, the father of modern biological taxonomy, Carl Linnaeus, listed among the types of quadrupeds familiar to him, the Latin word for dog, canis. Among the species within this genus, Linnaeus listed the fox, as Canis vulpes, wolves (Canis lupus), and the domestic dog, (Canis canis; see File:Linnaeus - Regnum Animale (1735).png) Sony VAIO PCG-8161M battery.

In later editions, Linnaeus dropped Canis canis and greatly expanded his list of the Canis genus of quadrupeds, and by 1758 included alongside the foxes, wolves, and jackels and many more terms that are now listed as synonyms for domestic dog, including aegyptius (hairless dog), aquaticus, (water dog), and mustelinus (literally “badger dog)” Sony VAIO PCG-8141M battery. Among these were two that later experts have been widely used for domestic dogs as a species: Canis domesticus and, most predominantly, Canis familiaris, the “common” or “familiar” dog.[23]

The domestic dog was accepted as a species in its own right until overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single speciesSony VAIO PCG-3J1M battery, the gray wolf, is the common ancestor for all breeds of domestic dogs. In recognition of this fact, the domestic dog was reclassified in 1993 as Canis lupus familiaris, a subspecies of the gray wolf Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists. C. l. familiaris is listed as the name for the taxon that is broadly used in the scientific community and recommended by ITIS, although Canis familiaris is a recognised synonym. Sony VAIO PCG-3H1M battery

Since that time, C. domesticus and all taxa referring to domestic dogs or subspecies of dog listed by Linnaeus, Johann Friedrich Gmelin in 1792, and Christian Smith in 1839, lost their subspecies status and have been listed as taxonomic synonyms for Canis lupus familiaris

History and evolution

Main articles: Origin of the domestic dog and Gray wolf

Ancient Greek rhyton in the shape of a dog's head, made by Brygos, early 5th century BC. Jérôme Carcopino Museum, Department of Archaeology, AleriaSony VAIO PCG-3F1M battery

Domestic dogs inherited complex behaviors from their wolf ancestors, which would have been pack hunters with complex body language. These sophisticated forms of social cognition and communication may account for their trainability, playfulness, and ability to fit into human households and social situations, and these attributes have given dogs a relationship with humans that has enabled them to become one of the most successful species on the planet today. 
Sony VAIO PCG-3C1M battery

Although experts largely disagree over the details of dog domestication, it is agreed that human interaction played a significant role in shaping the subspecies.[29] Domestication may have occurred initially in separate areas particularly Siberia and Europe. Currently it is thought domestication of our current lineage of dog occurred sometime as early as 15,000 years ago and arguably as late as 8500 years agoSony VAIO PCG-9Z2L battery. Shortly after the latest domestication, dogs became ubiquitous in human populations, and spread throughout the world.

Emigrants from Siberia likely crossed the Bering Strait with dogs in their company, and some experts[who?] suggest the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago,[citation needed] although the earliest archaeological evidence of dog-like canids in North America dates from about 9,000 years agoSony VAIO PCG-9Z1L battery.[30] Dogs were an important part of life for the Athabascan population in North America, and were their only domesticated animal. Dogs also carried much of the load in the migration of the Apache and Navajo tribes 1,400 years ago. Use of dogs as pack animals in these cultures often persisted after the introduction of the horse to North America. Sony VAIO PCG-9131L battery

The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate, although more recent evidence shows isolated domestication events as early as 33,000 years ago. There is conclusive evidence the present lineage of dogs genetically diverged from their wolf ancestors at least 15,000 years agoSony VAIO PCG-8161L battery, but some believe domestication to have occurred earlier.[29] Evidence is accruing that there were previous domestication events, but that those lineages died out.[7]

It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domesticationSony VAIO PCG-8152L battery. For example, it is hypothesized that some wolves gathered around the campsites of paleolithic camps to scavenge refuse, and associated evolutionary pressure developed that favored those who were less frightened by, and keener in approaching, humans.

Tesem, an old Egyptian sighthound-like dog.

The bulk of the scientific evidence for the evolution of the domestic dog stems from morphological studies of archaeological findings and mitochondrial DNA studiesSony VAIO PCG-8141L battery. The divergence date of roughly 15,000 years ago is based in part on archaeological evidence that demonstrates the domestication of dogs occurred more than 15,000 years ago, and some genetic evidence indicates the domestication of dogs from their wolf ancestors began in the late Upper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago. Sony VAIO PCG-8131L battery But there is a wide range of other, contradictory findings that make this issue controversial.[citation needed] There are findings beginning currently at 33,000 years ago distinctly placing them as domesticated dogs evidenced not only by shortening of the muzzle but widening as well as crowding of teeth.

Archaeological evidence suggests the latest dogs could have diverged from wolves was roughly 15,000 years ago, although it is possible they diverged much earlier. Sony VAIO PCG-81312L battery In 2008, a team of international scientists released findings from an excavation at Goyet Cave in Belgium declaring a large, toothy canine existed 31,700 years ago and ate a diet of horse, musk ox and reindeer.[37]

Prior to this Belgian discovery, the earliest dog fossils were two large skulls from Russia and a mandible from Germany dated from roughly 14,000 years ago. Sony VAIO PCG-81214L batteryRemains of smaller dogs from Natufian cave deposits in the Middle East, including the earliest burial of a human being with a domestic dog, have been dated to around 10,000 to 12,000 years ago.[5][38] There is a great deal of archaeological evidence for dogs throughout Europe and Asia around this period and through the next two thousand years (roughly 8,000 to 10,000 years ago) Sony VAIO PCG-81115L battery, with fossils uncovered in Germany, the French Alps, and Iraq, and cave paintings in Turkey.[24] The oldest remains of a domesticated dog in the Americas were found in Texas and have been dated to about 9,400 years ago.[39]

DNA studies

DNA studies have provided a wide range of possible divergence dates, from 15,000 to 40,000 years ago,[5] to as much as 100,000 to 140,000 years ago.[40] These results depend on a number of assumptions. Sony VAIO PCG-81114L battery Genetic studies are based on comparisons of genetic diversity between species, and depend on a calibration date. Some estimates of divergence dates from DNA evidence use an estimated wolf-coyote divergence date of roughly 700,000 years ago as a calibration.[41] If this estimate is incorrect, and the actual wolf-coyote divergence is closer to one or two million years ago, or more, then the DNA evidence that supports specific dog-wolf divergence dates would be interpreted very differentlySony VAIO PCG-81113L battery.

Furthermore, it is believed the genetic diversity of wolves has been in decline for the last 200 years, and that the genetic diversity of dogs has been reduced by selective breeding. This could significantly bias DNA analyses to support an earlier divergence date. The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptionsSony VAIO PCG-7142L battery. These conclusions are based on the location of maximal genetic divergence, and assume hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines.[24]

Genetic analyses indicate all dogs are likely descended from a handful of domestication events with a small number of founding females, Sony VAIO PCG-7141L battery although there is evidence domesticated dogs interbred with local populations of wild wolves on several occasions.[5] Data suggest dogs first diverged from wolves in East Asia, and these domesticated dogs then quickly migrated throughout the world, reaching the North American continent around 8000 BC.[5] The oldest groups of dogs, which show the greatest genetic variability and are the most similar to their wolf ancestorsSony VAIO PCG-71111L battery, are primarily Asian and African breeds, including the Basenji, Lhasa Apso, and Siberian Husky.[43] Some breeds thought to be very old, such as the Pharaoh Hound, Ibizan Hound, and Norwegian Elkhound, are now known to have been created more recently.[43]

A great deal of controversy surrounds the evolutionary framework for the domestication of dogs.[24] Although it is widely claimed that "man domesticated the wolf," Sony VAIO PCG-61411L battery man may not have taken such a proactive role in the process.[24] The nature of the interaction between man and wolf that led to domestication is unknown and controversial. At least three early species of the Homo genus began spreading out of Africa roughly 400,000 years ago, and thus lived for a considerable time in contact with canine species. Sony VAIO PCG-61112L battery

Despite this, there is no evidence of any adaptation of canine species to the presence of the close relatives of modern man. If dogs were domesticated, as believed, roughly 15,000 years ago, the event (or events) would have coincided with a large expansion in human territory and the development of agricultureSony VAIO PCG-61111L battery. This has led some biologists to suggest one of the forces that led to the domestication of dogs was a shift in human lifestyle in the form of established human settlements. Permanent settlements would have coincided with a greater amount of disposable food and would have created a barrier between wild and anthropogenic canine populations. Sony VAIO PCG-5T4L battery

Roles with humans

A Siberian Husky used as a pack animal

Early roles

Wolves, and their dog descendants, would have derived significant benefits from living in human camps—more safety, more reliable food, lesser caloric needs, and more chance to breed.[45] They would have benefited from humans’ upright gait that gives them larger range over which to see potential predators and prey, as well as color vision that, at least by day, gives humans better visual discrimination. Sony VAIO PCG-5T3L batteryCamp dogs would also have benefitted from human tool use, as in bringing down larger prey and controlling fire for a range of purposes.[45]

Humans would also have derived enormous benefit from the dogs associated with their camps.[46] For instance, dogs would have improved sanitation by cleaning up food scraps.[46] Dogs may have provided warmth, as referred to in the Australian Aboriginal expression “three dog night” (an exceptionally cold night) Sony VAIO PCG-5T2L battery, and they would have alerted the camp to the presence of predators or strangers, using their acute hearing to provide an early warning.[46]

Anthropologists believe the most significant benefit would have been the use of dogs' sensitive sense of smell to assist with the hunt.[46] The relationship between the presence of a dog and success in the hunt is often mentioned as a primary reason for the domestication of the wolfSony VAIO PCG-5S3L battery, and a 2004 study of hunter groups with and without a dog gives quantitative support to the hypothesis that the benefits of cooperative hunting was an important factor in wolf domestication.[47]

The cohabitation of dogs and humans would have greatly improved the chances of survival for early human groups, and the domestication of dogs may have been one of the key forces that led to human success. Sony VAIO PCG-5S2L battery

A British Bulldog shares a day at the park.

As pets

"The most widespread form of interspecies bonding occurs between humans and dogs"[46] and the keeping of dogs as companions, particularly by elites, has a long history.[49] However, pet dog populations grew significantly after World War II as suburbanization increased.[49] In the 1950s and 1960s, dogs were kept outside more often than they tend to be today Sony VAIO PCG-5S1L battery (using the expression “in the doghouse” to describe exclusion from the group signifies the distance between the doghouse and the home) and were still primarily functional, acting as a guard, children’s playmate, or walking companion. From the 1980s, there have been changes in the role of the pet dog, such as the increased role of dogs in the emotional support of their owners. Sony VAIO PCG-5R2L battery People and dogs have become increasingly integrated and implicated in each other’s lives,[52] to the point where pet dogs actively shape the way a family and home are experienced.[53]

There have been two major trends in the changing status of pet dogs. The first has been the ‘commodification’ of the dog, shaping it to conform to human expectations of personality and behaviour.[53] The second has been the broadening of the concept of the family and the home to include dogs-as-dogs within everyday routines and practices. Sony VAIO PCG-5R1L battery

There are a vast range of commodity forms available to transform a pet dog into an ideal companion.[54] The list of goods, services and places available is enormous: from dog perfumes, couture, furniture and housing, to dog groomers, therapists, trainers and care-takers, dog cafes, spas, parks and beaches, and dog hotels, airlines and cemeteries. Sony VAIO PCG-5P4L battery While dog training as an organized activity can be traced back to the 18th century, in the last decades of the 20th century it became a high profile issue as many normal dog behaviors such as barking, jumping up, digging, rolling in dung, fighting, and urine marking became increasingly incompatible with the new role of a pet dog.[55] Dog training books, classes and television programs proliferated as the process of commodifying the pet dog continued. Sony VAIO PCG-5P2L battery

A pet dog taking part in Christmas traditions

The majority of contemporary dog owners describe their dog as part of the family,[53] although some ambivalence about the relationship is evident in the popular reconceptualization of the dog-human family as a pack.[53] A dominance model of dog-human relationships has been promoted by some dog trainers, such as on the television program Dog WhispererSony VAIO PCG-5N4L battery. However it has been disputed that "trying to achieve status" is characteristic of dog–human interactions.[57] Pet dogs play an active role in family life; for example, a study of conversations in dog-human families showed how family members use the dog as a resource, talking to the dog, or talking through the dog, to mediate their interactions with each other.Sony VAIO PCG-5N2L battery

Another study of dogs’ roles in families showed many dogs have set tasks or routines undertaken as family members, the most common of which was helping with the washing-up by licking the plates in the dishwasher, and bringing in the newspaper from the lawn.[53] Increasingly, human family members are engaging in activities centred on the perceived needs and interests of the dog, or in which the dog is an integral partner, such as Dog Dancing and Doga. Sony VAIO PCG-51513L battery

According to the statistics published by the American Pet Products Manufacturers Association in the National Pet Owner Survey in 2009–2010, it is estimated there are 77.5 million dog owners in the United States.[59] The same survey shows nearly 40% of American households own at least one dog, of which 67% own just one dogSony VAIO PCG-51511L battery, 25% two dogs and nearly 9% more than two dogs. There does not seem to be any gender preference among dogs as pets, as the statistical data reveal an equal number of female and male dog pets. Yet, although several programs are undergoing to promote pet adoption, less than a fifth of the owned dogs come from a shelterSony VAIO PCG-51412L battery.

Work

Dogs have lived and worked with humans in so many roles that they have earned the unique nickname, "man's best friend",[60] a phrase used in other languages as well. They have been bred for herding livestock,[61] hunting (e.g. pointers and hounds),[62] rodent control,[3] guarding, helping fishermen with nets, detection dogs, and pulling loads, in addition to their roles as companionsSony VAIO PCG-51411L battery.

Book of the Hunt, Gaston III, Count of Foix, 1387–88.

Service dogs such as guide dogs, utility dogs, assistance dogs, hearing dogs, and psychological therapy dogs provide assistance to individuals with physical or mental disabilities.[63][64] Some dogs owned by epileptics have been shown to alert their handler when the handler shows signs of an impending seizure, sometimes well in advance of onset, allowing the owner to seek safety, medication, or medical care. Sony VAIO PCG-51312L battery

Dogs included in human activities in terms of helping out humans are usually called working dogs. Dogs of several breeds are considered working dogs. Some working dog breeds include Akita, Alaskan Malamute, Anatolian Shepherd Dog, Bernese Mountain Dog, Black Russian Terrier, Boxer, Bullmastiff, Doberman Pinscher, Dogue de Bordeaux, German Pinscher, German Shepherd, Sony VAIO PCG-51311L batteryGiant Schnauzer, Great Dane, Great Pyrenees, Great Swiss Mountain Dog, Komondor, Kuvasz, Mastiff, Neapolitan Mastiff, Newfoundland, Portuguese Water Dog, Rottweiler, Saint Bernard, Samoyed, Siberian Husky, Standard Schnauzer, and Tibetan Mastiff.

Sports and shows

See also: Conformation show

Owners of dogs often enter them in competitions[67] such as breed conformation shows or sports, including racing and sledding.

In conformation shows, also referred to as breed shows, a judge familiar with the specific dog breed evaluates individual purebred dogs for conformity with their established breed type as described in the breed standardSony VAIO PCG-51211L battery. As the breed standard only deals with the externally observable qualities of the dog (such as appearance, movement, and temperament), separately tested qualities (such as ability or health) are not part of the judging in conformation shows.

As a food source

See also: Dog meat

Fried dog meat offered as speciality, among lamb and fish. Shaoyang, Hunan Province, China

Dog meat is consumed in some East Asian countries, including Korea, China, and Vietnam, a practice that dates back to antiquity. Sony VAIO PCG-41112L battery It is estimated that 13–16 million dogs are killed and consumed in Asia every year.[69] The BBC claims that, in 1999, more than 6,000 restaurants served soups made from dog meat in South Korea.[70] In Korea, the primary dog breed raised for meat, the nureongi (누렁이), differs from those breeds raised for pets that Koreans may keep in their homes. Sony VAIO PCG-3A4L battery

The most popular Korean dog dish is gaejang-guk (also called bosintang), a spicy stew meant to balance the body's heat during the summer months; followers of the custom claim this is done to ensure good health by balancing one's gi, or vital energy of the body. A 19th century version of gaejang-guk explains that the dish is prepared by boiling dog meat with scallions and chili powderSony VAIO PCG-3A3L battery. Variations of the dish contain chicken and bamboo shoots. While the dishes are still popular in Korea with a segment of the population, dog is not as widely consumed as beef, chicken, and pork.

Other cultures, such as Polynesia and pre-Columbian Mexico, also consumed dog meat in their history. However, Western, South Asian, African, and Middle Eastern cultures, in general, regard consumption of dog meat as tabooSony VAIO PCG-3A2L battery. In some places, however, such as in rural areas of Poland, dog fat is believed to have medicinal properties—being good for the lungs for instance.[73]

A CNN report in China dated March 2010 interviews a dog meat vendor who states that most of the dogs that are available for selling to restaurant are raised in special farms but that there is always a chance that a sold dog is someone's lost pet, although dog pet breeds are not considered edible. Sony VAIO PCG-3A1L battery

Health risks to humans

Main article: Dog attack

It is estimated that two percent of the US population, 4.7 million people, are bitten each year.[75] In the 1980s and 1990s the US averaged 17 fatalities per year, while in the 2000s this has increased to 26. 77% of dog bites are from the pet of family or friends, and 50% of attacks occur on the dog owner's property. Sony VAIO PCG-394L battery

A Colorado study found bites in children were less severe than bites in adults.[77] The incidence of dog bites in the U.S. is 12.9 per 10,000 inhabitants, but for boys aged 5 to 9, the incidence rate is 60.7 per 10,000. Moreover, children have a much higher chance to be bitten in the face or neck.[78] Sharp claws with powerful muscles behind them can lacerate flesh in a scratch that can lead to serious infections. Sony VAIO PCG-393L battery

In the UK between 2003 and 2004, there were 5,868 dog attacks on humans, resulting in 5,770 working days lost in sick leave.[80]

In the United States, cats and dogs are a factor in more than 86,000 falls each year.[81] It has been estimated around 2% of dog-related injuries treated in UK hospitals are domestic accidents. The same study found that while dog involvement in road traffic accidents was difficult to quantify, dog-associated road accidents involving injury more commonly involved two-wheeled vehicles. Sony VAIO PCG-391L battery

Toxocara canis (dog roundworm) eggs in dog feces can cause toxocariasis. In the United States, about 10,000 cases of Toxocara infection are reported in humans each year, and almost 14% of the U.S. population is infected.[83] In Great Britain, 24% of soil samples taken from public parks contained T. canis eggs.[84] Untreated toxocariasis can cause retinal damage and decreased vision. Sony VAIO PCG-384L battery Dog feces can also contain hookworms that cause cutaneous larva migrans in humans.

Health benefits for humans

A human cuddles a Doberman puppy.

A growing body of research indicates the companionship of a dog can enhance human physical health and psychological wellbeing.[89] Dog and cat owners have been shown to have better mental and physical health than nonowners, making fewer visits to the doctor and being less likely to be on medication than nonowners. Sony VAIO PCG-383L battery In one study, new pet owners reported a highly significant reduction in minor health problems during the first month following pet acquisition, and this effect was sustained in dog owners through to the end of the study.[91]

In addition, dog owners took considerably more physical exercise than cat owners and people without pets. The group without pets exhibited no statistically significant changes in health or behaviourSony VAIO PCG-382L battery. The results provide evidence that pet acquisition may have positive effects on human health and behaviour, and that for dog owners these effects are relatively long term.[91] Pet ownership has also been associated with increased coronary artery disease survival, with dog owners being significantly less likely to die within one year of an acute myocardial infarction than those who did not own dogs.Sony VAIO PCG-381L battery

Gunnar Kaasen and Balto, the lead dog on the last relay team of the 1925 serum run to Nome.

The health benefits of dogs can result from contact with dogs, not just from dog ownership. For example, when in the presence of a pet dog, people show reductions in cardiovascular, behavioral, and psychological indicators of anxiety. Sony VAIO PCG-7185L battery The benefits of contact with a dog also include social support, as dogs are able to not only provide companionship and social support themselves, but also to act as facilitators of social interactions between humans.[94] One study indicated that wheelchair users experience more positive social interactions with strangers when they are accompanied by a dog than when they are not. Sony VAIO PCG-7184L battery

The practice of using dogs and other animals as a part of therapy dates back to the late 18th century, when animals were introduced into mental institutions to help socialize patients with mental disorders.[96] Animal-assisted intervention research has shown that animal-assisted therapy with a dog can increase a person with Alzheimer’s disease’s social behavioursSony VAIO PCG-7183L battery, such as smiling and laughing.[97] One study demonstrated that children with ADHD and conduct disorders who participated in an education program with dogs and other animals showed increased attendance, increased knowledge and skill objectives, and decreased antisocial and violent behavior compared to those who were not in an animal-assisted program. Sony VAIO PCG-7182L battery

Shelters

Main article: Animal shelter

Every year, between 6 and 8 million dogs and cats enter US animal shelters.[99] The Humane Society of the United States (HSUS) estimates that approximately 3 to 4 million dogs and cats are euthanized yearly in shelters across the United States. However, the percentage of dogs in US animal shelters that are eventually adopted and removed from the sheltersSony VAIO PCG-7181L battery by their new owners has increased since the mid 1990s from around 25% up to around 60–75% in the mid first decade of the 21st century.[101]

Pets entering the shelters are euthanized in countries all over the world because of the lack of financial provisions to take care of these animals. Most shelters complain of not having enough resources to feed the pets and by being constrained to kill them, as the likelihood for all of them to find an owner is very small. In poor countries, euthanasia is usually violentSony VAIO PCG-7174L battery.

Biology

Main article: Dog anatomy

Lateral view of a dog's bone structure.

Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes.[3] Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Nevertheless, their morphology is based on that of their wild ancestors, gray wolves.[3] Dogs are predators and scavengersSony VAIO PCG-7173L battery, and like many other predatory mammals, the dog has powerful muscles, fused wrist bones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.

Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 centimetres (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz)Sony VAIO PCG-7172L battery. The largest known dog was an English Mastiff which weighed 155.6 kilograms (343 lb) and was 250 cm (98 in) from the snout to the tail.[102] The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.

Senses

Vision

Dog's visual colour perception compared with humans.

Like most mammals, dogs are dichromats and have color vision equivalent to red-green color blindness in humans (deuteranopia). Dogs are less sensitive to differences in grey shades than humans and also can detect brightness at about half the accuracy of humans. Sony VAIO PCG-7171L battery

The dog's visual system has evolved to aid proficient hunting.[104] While a dog's visual acuity is poor (that of a poodle's has been estimated to translate to a Snellen rating of 20/75[104]), their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (e.g., identifying their owner) at a range of between 800 and 900 m, however this range decreases to 500–600 m if the object is stationary. Sony VAIO PCG-7162L battery

Dogs have a temporal resolution of between 60 and 70 Hz, which explains why many dogs struggle to watch television, as most such modern screens are optimized for humans at 50–60 Hz.[108] Dogs can detect a change in movement that exists in a single diopter of space within their eye. Humans, by comparison, require a change of between 10 and 20 diopters to detect movementSony VAIO PCG-7161L battery.

The physiology of a dog ear.

As crepuscular hunters, dogs often rely on their vision in low light situations: They have very large pupils, a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum.[104] The tapetum is a reflective surface behind the retina that reflects light to give the photoreceptors a second chance to catch the photons. There is also a relationship between body size and overall diameter of the eyeSony VAIO PCG-7154L battery. A range of 9.5 and 11.6 mm can be found between various breeds of dogs. This 20% variance can be substantial and is associated as an adaptation toward superior night vision.[111]

The eyes of different breeds of dogs have different shapes, dimensions, and retina configurations.[112] Many long-nosed breeds have a "visual streak" – a wide foveal region that runs across the width of the retina and gives them a very wide field of excellent visionSony VAIO PCG-7153L battery. Some long-muzzled breeds, in particular, the sighthounds, have a field of vision up to 270° (compared to 180° for humans). Short-nosed breeds, on the other hand, have an "area centralis": a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's. Some broad-headed breeds with short noses have a field of vision similar to that of humans. Sony VAIO PCG-7152L battery

Most breeds have good vision, but some show a genetic predisposition for myopia – such as Rottweilers, with which one out of every two has been found to be myopic.[104] Dogs also have a greater divergence of the eye axis than humans, enabling them to rotate their pupils farther in any direction. The divergence of the eye axis of dogs ranges from 12–25° depending on the breed.Sony VAIO PCG-7151L battery

Experimentation has proven that dogs can distinguish between complex visual images such as that of a cube or a prism. Dogs also show attraction to static visual images such as the silhouette of a dog on a screen, their own reflections, or videos of dogs; however, their interest declines sharply once they are unable to make social contact with the image. 
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Hearing

The frequency range of dog hearing is approximately 40 Hz to 60,000 Hz,[114] which means that dogs can detect sounds far beyond the upper limit of the human auditory spectrum. In addition, dogs have ear mobility, which allows them to rapidly pinpoint the exact location of a sound. Eighteen or more muscles can tilt, rotate, raise, or lower a dog's earSony VPCW21M2E/WI battery. A dog can identify a sound's location much faster than a human can, as well as hear sounds at four times the distance.[116]

Smell

The wet, textured nose of a dog

While the human brain is dominated by a large visual cortex, the dog brain is dominated by an olfactory cortex.[104] The olfactory bulb in dogs is roughly forty times bigger than the olfactory bulb in humans, relative to total brain size, with 125 to 220 million smell-sensitive receptors.[104] The bloodhound exceeds this standard with nearly 300 million receptors. Sony VPCW21C7E battery

Consequently, it has been estimated that dogs, in general, have an olfactory sense ranging from one hundred thousand to one million times more sensitive than a human's. In some dog breeds, such as bloodhounds, the olfactory sense may be up to 100 million times greater than a human's.[117] The wet nose is essential for determining the direction of the air current containing the smellSony VPCW12S1E/WZ battery. Cold receptors in the skin are sensitive to the cooling of the skin by evaporation of the moisture by air currents.[118]

Physical characteristics

Main article: Dog anatomy

Coat

Main article: Coat (dog)

A heavy winter coat with countershading in a mixed-breed dog

The coats of domestic dogs are of two varieties: "double" being common with dogs (as well as wolves) originating from colder climates, made up of a coarse guard hair and a soft down hair, or "single", with the topcoat onlySony VPCW12S1E/W battery.

Domestic dogs often display the remnants of countershading, a common natural camouflage pattern. A countershaded animal will have dark coloring on its upper surfaces and light coloring below,[119] which reduces its general visibility. Thus, many breeds will have an occasional "blaze", stripe, or "star" of white fur on their chest or underside. Sony VPCW12S1E/T battery

Tail

See also: Docking

There are many different shapes for dog tails: straight, straight up, sickle, curled, or cork-screw. As with many canids, one of the primary functions of a dog's tail is to communicate their emotional state, which can be important in getting along with others. In some hunting dogs, however, the tail is traditionally docked to avoid injuries.[121] In some breeds, puppies can be born with a short tail or no tail at allSony VPCW12S1E/P battery.

Types and breeds

Main article: Dog breed

Further information: Dog type

Cavalier King Charles Spaniels demonstrate with-breed variation.

While all dogs are genetically very similar,[5] natural selection and selective breeding have reinforced certain characteristics in certain populations of dogs, giving rise to dog types and dog breeds. Dog types are broad categories based on function, genetics, or characteristics.[123] Dog breeds are groups of animals that possess a set of inherited characteristics that distinguishes them from other animals within the same speciesSony VPCW11S1E/W battery. Modern dog breeds are non-scientific classifications of dogs kept by modern kennel clubs.

Purebred dogs of one breed are genetically distinguishable from purebred dogs of other breeds,[43] but the means by which kennel clubs classify dogs is unsystematic. Systematic analyses of the dog genome has revealed only four major types of dogs that can be said to be statistically distinct.[43] These include the "old world dogs" (e.g., Malamute and Shar Pei) Sony VPCW11S1E/T battery, "Mastiff"-type (e.g., English Mastiff), "herding"-type (e.g., Border Collie), and "all others" (also called "modern"- or "hunting"-type).

Health

Main article: Dog health

Further information: Category:Dog health

See also: CVBD

Dogs are susceptible to various diseases, ailments, and poisons, some of which can affect humans. To defend against many common diseases, dogs are often vaccinated.

A mixed-breed dog

Some breeds of dogs are prone to certain genetic ailments such as elbow or hip dysplasia, blindness, deafness, pulmonic stenosis, cleft palate, and trick knees. Two serious medical conditions particularly affecting dogs are pyometra, affecting unspayed females of all types and agesSony VPCW11S1E/P battery, and bloat, which affects the larger breeds or deep-chested dogs. Both of these are acute conditions, and can kill rapidly. Dogs are also susceptible to parasites such as fleas, ticks, and mites, as well as hookworm, tapeworm, roundworm, and heartworm.

Dogs are highly susceptible to theobromine poisoning, typically from ingestion of chocolate. Theobromine is toxic to dogs because, although the dog's metabolism is capable of breaking down the chemicalSony VPCYA1S1E/B battery, the process is so slow that even small amounts of chocolate can be fatal, especially dark chocolate.

Dogs are also vulnerable to some of the same health conditions as humans, including diabetes, dental and heart disease, epilepsy, cancer, hypothyroidism, and arthritis.[125]

Mortality

Main article: Aging in dogs

The typical lifespan of dogs varies widely among breeds, but for most the median longevity, the age at which half the dogs in a population have died and half are still alive, ranges from 10 to 13 years. Individual dogs may live well beyond the median of their breedSony VPCYA1V9E/B battery.

The breed with the shortest lifespan (among breeds for which there is a questionnaire survey with a reasonable sample size) is the Dogue de Bordeaux, with a median longevity of about 5.2 years, but several breeds, including Miniature Bull Terriers, Bloodhounds, and Irish Wolfhounds are nearly as short-lived, with median longevities of 6 to 7 years. Sony VPCY21S1E/SI battery

The longest-lived breeds, including Toy Poodles, Japanese Spitz, Border Terriers, and Tibetan Spaniels, have median longevities of 14 to 15 years.[129] The median longevity of mixed-breed dogs, taken as an average of all sizes, is one or more years longer than that of purebred dogs when all breeds are averaged. The dog widely reported to be the longest-lived is "Bluey," Sony VPCY21S1E/L batterywho died in 1939 and was claimed to be 29.5 years old at the time of his death; however, the Bluey record is anecdotal and unverified.[131] On December 5, 2011, Pusuke, the world's oldest living dog recognized by Guinness Book of World Records, died aged 26 years and 9 months.[132]

Predation

Although wild dogs, like wolves, are apex predators, they can be killed in territory disputes with wild animals. Sony VPCY21S1E/G batteryFurthermore, in areas where both dogs and other large predators live, dogs can be a major food source for big cats or canines. Reports from Croatia indicate wolves kill dogs more frequently than they kill sheep. Wolves in Russia apparently limit feral dog populations. In Wisconsin, more compensation has been paid for dog losses than livestock.[133] Some wolf pairs have been reported to prey on dogs by having one wolf lure the dog out into heavy brush where the second animal waits in ambush. Sony VPCY11S1E/S battery In some instances, wolves have displayed an uncharacteristic fearlessness of humans and buildings when attacking dogs, to the extent that they[which?] have to be beaten off or killed.[135]

Coyotes and big cats have also been known to attack dogs. Leopards in particular are known to have a predilection for dogs, and have been recorded to kill and consume them regardless of the dog's size or ferocity.[136] Tigers in Manchuria, Indochina, Indonesia, and Malaysia are reputed to kill dogs with the same vigor as leopards. Sony VPCY11S1E battery Striped Hyenas are major predators of village dogs in Turkmenistan, India, and the Caucasus.[138] Reptiles such as alligators and pythons have been known to kill and eat dogs.

Diet

Dog food

Golden Retriever gnawing a pig's foot

Despite their descent from wolves and classification as Carnivora, dogs are variously described in scholarly and other writings as carnivores or omnivores. Unlike obligate carnivores, such as the cat family with its shorter small intestineSony VPCZ11X9E/B battery, dogs can adapt to a wide-ranging diet, and are not dependent on meat-specific protein nor a very high level of protein in order to fulfill their basic dietary requirements. Dogs will healthily digest a variety of foods, including vegetables and grains, and can consume a large proportion of these in their diet. Sony VPCZ11Z9E/B battery

A number of common human foods and household ingestibles are toxic to dogs, including chocolate solids (theobromine poisoning), onion and garlic (thiosulphate, sulfoxide or disulfide poisoning),[144] grapes and raisins, macadamia nuts, as well as various plants and other potentially ingested materialsSony VPCZ12M9E/B battery.

Reproduction

Two dogs copulating on a beach

Main article: Canine reproduction

In domestic dogs, sexual maturity begins to happen around age six to twelve months for both males and females,[3][147] although this can be delayed until up to two years old for some large breeds. This is the time at which female dogs will have their first estrous cycle. They will experience subsequent estrous cycles biannually, during which the body prepares for pregnancySony VPCZ12X9E/X battery. At the peak of the cycle, females will come into estrus, being mentally and physically receptive to copulation.[3] Because the ova survive and are capable of being fertilized for a week after ovulation, it is possible for a female to mate with more than one male.[3]

Dogs bear their litters roughly 56 to 72 days after fertilization,[3][148] with an average of 63 days, although the length of gestation can vary. An average litter consists of about six puppies, Sony VPCZ12Z9E/X battery though this number may vary widely based on the breed of dog. In general, toy dogs produce from one to four puppies in each litter, while much larger breeds may average as many as twelve.

Some dog breeds have acquired traits through selective breeding that interfere with reproduction. Male French Bulldogs, for instance, are incapable of mounting the female. For many dogs of this breed, the female must be artificially inseminated in order to reproduce. Sony VPCZ138GA battery

Neutering

The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page. (March 2012)

A feral dog from Sri Lanka nursing her four puppies

Neutering refers to the sterilization of animals, usually by removal of the male's testicles or the female's ovaries and uterus, in order to eliminate the ability to procreate and reduce sex driveSony VPCZ13M9E/B battery. Because of the overpopulation of dogs in some countries, many animal control agencies, such as the American Society for the Prevention of Cruelty to Animals (ASPCA), advise that dogs not intended for further breeding should be neutered, so that they do not have undesired puppies that may have to later be euthanized.[151]

According to the Humane Society of the United States, 3–4 million dogs and cats are put down each year in the United States and many more are confined to cages in shelters because there are many more animals than there are homesSony VPCZ13M9E/X battery. Spaying or castrating dogs helps keep overpopulation down.[152] Local humane societies, SPCAs, and other animal protection organizations urge people to neuter their pets and to adopt animals from shelters instead of purchasing them.

Neutering reduces problems caused by hypersexuality, especially in male dogs.[153] Spayed female dogs are less likely to develop some forms of cancer, affecting mammary glands, ovaries, and other reproductive organs. Sony VPCZ13V9E batteryHowever, neutering increases the risk of urinary incontinence in female dogs,[155] and prostate cancer in males,[156] as well as osteosarcoma, hemangiosarcoma, cruciate ligament rupture, obesity, and diabetes mellitus in either gender.[157]

Intelligence and behavior

Intelligence

Main article: Dog intelligence

The Border Collie is considered to be one of the most intelligent breeds.

The domestic dog has a predisposition to exhibit a social intelligence that is uncommon in the animal world.[104] Dogs are capable of learning in a number of ways, such as through simple reinforcement (e.g., classical or operant conditioning) and by observation. Sony VPCZ13V9E/X battery

Dogs go through a series of stages of cognitive development. As with humans, the understanding that objects not being actively perceived still remain in existence (called object permanence) is not present at birth. It develops as the young dog learns to interact intentionally with objects around it, at roughly 8 weeks of age. Sony VPCZ13Z9E/X battery

Puppies learn behaviors quickly by following examples set by experienced dogs.[104] This form of intelligence is not peculiar to those tasks dogs have been bred to perform, but can be generalized to myriad abstract problems. For example, Dachshund puppies that watched an experienced dog pull a cart by tugging on an attached piece of ribbon in order to get a reward from inside the cart learned the task fifteen times faster than those left to solve the problem on their own. Sony VPCZ21M9E battery

Dogs can also learn by mimicking human behaviors. In one study, puppies were presented with a box, and shown that, when a handler pressed a lever, a ball would roll out of the box. The handler then allowed the puppy to play with the ball, making it an intrinsic reward. The pups were then allowed to interact with the box. Roughly three-quarters of the puppies subsequently touched the leverSony VPCZ21Q9E battery, and over half successfully released the ball, compared to only 6% in a control group that did not watch the human manipulate the lever.[159] Another study found that handing an object between experimenters who then used the object's name in a sentence successfully taught an observing dog each object's name, allowing the dog to subsequently retrieve the item. Sony VPCZ21V9E battery

Sergeant Stubby wearing his uniform and medals. Stubby participated in four offensives and 17 battles.

Dogs also demonstrate sophisticated social cognition by associating behavioral cues with abstract meanings.[104] One such class of social cognition involves the understanding that others are conscious agents. Research has shown that dogs are capable of interpreting subtle social cuesSony VPCEH3T9E battery, and appear to recognize when a human or dog's attention is focused on them. To test this, researchers devised a task in which a reward was hidden underneath one of two buckets. The experimenter then attempted to communicate with the dog to indicate the location of the reward by using a wide range of signals: tapping the bucket, pointing to the bucket, nodding to the bucket, or simply looking at the bucket. Sony VPCEH3N6E battery The results showed that domestic dogs were better than chimpanzees, wolves, and human infants at this task, and even young puppies with limited exposure to humans performed well.[104]

Psychology research has shown that humans´ gaze instinctively moves to the left in order to watch the right side of a person's face, which is related to use of right hemisphere brain for facial recognition, including human facial emotions. Research at the University of Lincoln (2008) shows that dogs share this instinct when meeting a human beingSony VPCEH3N1E battery, and only when meeting a human being (i.e., not other animals or other dogs). As such they are the only non-primate species known to do so.[162][163]

Stanley Coren, an expert on dog psychology, states that these results demonstrated the social cognition of dogs can exceed that of even our closest genetic relatives, and that this capacity is a recent genetic acquisition that distinguishes the dog from its ancestor, the wolf. Sony VPCEH3D0E battery Studies have also investigated whether dogs engaged in partnered play change their behavior depending on the attention-state of their partner.[164] Those studies showed that play signals were only sent when the dog was holding the attention of its partner. If the partner was distracted, the dog instead engaged in attention-getting behavior before sending a play signal. Sony VPCEH3B1E battery

Coren has also argued that dogs demonstrate a sophisticated theory of mind by engaging in deception, which he supports with a number of anecdotes, including one example wherein a dog hid a stolen treat by sitting on it until the rightful owner of the treat left the room.[104] Although this could have been accidental, Coren suggests that the thief understood that the treat's owner would be unable to find the treat if it were out of viewSony VPCEH2Z1E battery. Together, the empirical data and anecdotal evidence points to dogs possessing at least a limited form of theory of mind.[104][164]

A study found a third of dogs suffered from anxiety when separated from others.[165]

A Border Collie named Chaser has learned the names for 1,022 toys after three years of training, so many that her trainers have had to mark the names of the objects lest they forget themselves. This is higher than Rico, another border collie who could remember at least 200 objects. Sony VPCEH2S9E battery

Behavior

Main article: Dog behavior

Further information: Category:Dog training and behavior

Although dogs have been the subject of a great deal of behaviorist psychology (e.g. Pavlov's dog), they do not enter the world with a psychological "blank slate".[104] Rather, dog behavior is affected by genetic factors as well as environmental factors.[104] Domestic dogs exhibit a number of behaviors and predispositions that were inherited from wolves. Sony VPCEH2Q1E battery

The Gray Wolf is a social animal that has evolved a sophisticated means of communication and social structure. The domestic dog has inherited some of these predispositions, but many of the salient characteristics in dog behavior have been largely shaped by selective breeding by humans. Thus some of these characteristics, such as the dog's highly developed social cognition, are found only in primitive forms in grey wolves. Sony VPCEH2P0E battery

The existence and nature of personality traits in dogs have been studied (15329 dogs of 164 different breeds) and five consistent and stable "narrow traits" identified, described as playfulness, curiosity/fearlessness, chase-proneness, sociability and aggressiveness. A further higher order axis for shyness–boldness was also identified. Sony VPCEH2N1E battery

Sleep

Further information: Sleep (non-human)

The average sleep time of a dog is said to be 10.1 hours per day.[169] Like humans, dogs have two main types of sleep: Slow-wave sleep, then Rapid eye movement sleep sleep, the state in which dreams occur.[170]

Dog growl

A new study in Budapest, Hungary has found that dogs are able to tell how big another dog is just by listening to its growl. A specific growl is used by dogs to protect their food. The research also shows that dogs do not lie about their sizeSony VPCEH2M9E battery, and this is the first time research has shown animals can determine another’s size by the sound it makes. The test, using images of many kinds of dogs, showed a small and big dog and played a growl. The result, showed that 20 of the 24 test dogs looked at the image of the appropriate-sized dog first and looked at it longest. Sony VPCEH2M1E battery

Differences from wolves

Some dogs, like this Tamaskan, look very much like wolves.

Physical characteristics

Further information: Wolf

Compared to equally sized wolves, dogs tend to have 20% smaller skulls, 30% smaller brains,[172] as well as proportionately smaller teeth than other canid species.[173] Dogs require fewer calories to function than wolves. It is thought by certain experts that the dog's limp ears are a result of atrophy of the jaw muscles.[173] The skin of domestic dogs tends to be thicker than that of wolvesSony VPCEH2L9E battery, with some Inuit tribes favoring the former for use as clothing due to its greater resistance to wear and tear in harsh weather.[173]

Behavior

Dogs tend to be poorer than wolves at observational learning, being more responsive to instrumental conditioning.[173] Feral dogs show little of the complex social structure or dominance hierarchy present in wolf packs. For example, unlike wolves, the dominant alpha pairs of a feral dog pack do not force the other members to wait for their turn on a meal when scavenging off a dead ungulate as the whole family is free to join inSony VPCEH2J1E battery. For dogs, other members of their kind are of no help in locating food items, and are more like competitors.[173]

Feral dogs are primarily scavengers, with studies showing that unlike their wild cousins, they are poor ungulate hunters, having little impact on wildlife populations where they are sympatric. However, feral dogs have been reported to be effective hunters of reptiles in the Galápagos Islands, Sony VPCEH2H1E battery and free ranging pet dogs are more prone to predatory behavior toward wild animals.

Domestic dogs can be monogamous.[175] Breeding in feral packs can be, but does not have to be restricted to a dominant alpha pair (such things also occur in wolf packs).[176] Male dogs are unusual among canids by the fact that they mostly seem to play no role in raising their puppies, and do not kill the young of other females to increase their own reproductive success. Sony VPCEH2F1E battery Some sources say that dogs differ from wolves and most other large canid species by the fact that they do not regurgitate food for their young, nor the young of other dogs in the same territory.[173]

An Australian Shepherd-Beagle mix displaying mastery of the "sit" command

However, this difference was not observed in all domestic dogs. Regurgitating of food by the females for the young as well as care for the young by the males has been observed in domestic dogsSony VPCEH2E0E battery, dingos as well as in other feral or semi-feral dogs. Regurgitating of food by the females and direct choosing of only one mate has been observed even in those semi-feral dogs of direct domestic dog ancestry. Also regurgitating of food by males has been observed in free-ranging domestic dogs.

Trainability

Dogs display much greater tractability than tame wolves, and are, in general, much more responsive to coercive techniques involving fearSony VPCEH2D0E battery, aversive stimuli, and force than wolves, which are most responsive toward positive conditioning and rewards.[178] Unlike tame wolves, dogs tend to respond more to voice than hand signals.[179]

Mythology

In mythology, dogs often serve as pets or as watchdogs.[180]

In Greek mythology, Cerberus is a three-headed watchdog who guards the gates of Hades.[180] In Norse mythology, a bloody, four-eyed dog called Garmr guards Helheim.[180] In Persian mythology, two four-eyed dogs guard the Chinvat Bridge. Sony VPCEH2C0E batteryIn Philippine mythology, Kimat who is the pet of Tadaklan, god of thunder, is responsible for lightning. In Welsh mythology, Annwn is guarded by Cŵn Annwn[180]

In Judaism and Islam, dogs are viewed as unclean scavengers.[180] In Christianity, dogs represent faithfulness.[180] In Asian countries such as China, Korea, and Japan, dogs are viewed as kind protectorsSony VPCEH1Z1E battery.