Rhinoceros
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| Rhinoceros Fossil range: Eocene–Recent | ||||||||||
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 Black Rhinoceros, Diceros bicornis | ||||||||||
| Scientific classification | ||||||||||
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| Extant Genera | ||||||||||
| Ceratotherium |
Rhinoceros (pronounced /raɪˈnɒsərəs/), often colloquially abbreviated rhino, is a name used to group five extant species of odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia. Three of the five species—the Javan, Sumatran and Black Rhinoceros—are critically endangered. The Indian is endangered, with fewer than 2,700 individuals remaining in the wild. The White is registered as "vulnerable", with approximately 17,500 remaining in the wild, as reported by the International Rhino Foundation.[1][2] The Rhinoceros Beetle is named as such due to its horns, which simulate rhino's horns.
The white rhino is actually not white at all. The name comes from the Dutch word wijde, meaning "wide", referring to the wide square mouth that allows the rhino to graze, as opposed to the black rhino which is a browser.
The rhinoceros family is characterized by its large size (one of the largest remaining megafauna alive today), with all of the species able to reach one ton or more in weight; herbivorous diet; and 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 (400–600g); 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.[3]
The rhino is prized for its horn. The horns of a rhinoceros are made of keratin, the same type of protein that makes up hair and fingernails.[4] Both African species and the Sumatran Rhinoceros have two horns, while the Indian and Javan Rhinoceros have a single horn. Rhinoceroses have acute hearing and sense of smell, but poor eyesight. Most live to be about 60 years old or more.
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[edit] Taxonomy and naming
The word rhinoceros is derived through Latin from the Greek ῥῑνόκερως, which is composed of ῥῑνο-, ῥίς (rhino-, rhis), meaning nose, and κέρας (keras), meaning horn. The standard plural in English is rhinoceroses (some dictionaries also list rhinoceri, although this is neither a proper Latin, Greek or English plural form). The collective noun for a group of rhinoceros is crash or herd.[5] They are commonly known as rhinos.
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. 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 wyd ("wide" in Afrikaans), referring to their square lips.[6]
White Rhinoceros are divided into Northern and Southern subspecies. There are two living Rhinocerotini species, the endangered Indian Rhinoceros and the critically endangered Javan Rhinoceros, which diverged from one another about 10 million years ago. The critically endangered Sumatran Rhinoceros is the only surviving representative of the most primitive group, the Dicerorhinini, which emerged in the Miocene (about 20 million years ago).[7] 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.[8]
All rhinoceros species have 82 chromosomes (diploid number, 2N, per cell), except the Black Rhinoceros, which has 84. This is the highest known chromosome number of all mammals.
[edit] White Rhinoceros
The White or Square-lipped Rhinoceros (Ceratotherium simum) is, after the elephant, the most massive remaining land animal in the world, along with the Indian Rhinoceros and the hippopotamus, which are of comparable size. 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), is down to as few as four individuals in the wild, and as of June 2008 this sub-species could even be extinct.[9]
The White Rhino has an immense body and large head, a short neck and broad chest. This rhino can exceed 3500 kg (6600 pounds), have a head-and-body length of 3.5-4.6 m (12-15.9 feet) and a shoulder height of 180-200 cm (5.85-6.56 feet) The record-sized White Rhinoceros was about 4600 kg (11,500 lb).[10] On its snout it has two horns. The front horn is larger than the other horn and averages 90 cm (23.6 inches) in length and can reach 150 cm (60 inches). 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. 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.
[edit] 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 colour. 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, western Botswana and western South Africa; East African (Diceros bicornis michaeli), primarily in Tanzania; and West African (Diceros bicornis longipes) which was tentatively declared extinct in 2006. Only 8 of this subspecies are left in existence, all in captivity.[11]
An adult Black Rhinoceros stands 150–175 cm (59–67inches) high at the shoulder and is 3.5-3.9 m (11–12.2 feet) in length.[12] An adult weighs from 850 to 1600 kg (1,800 to 3,200 lb), exceptionally to 1820 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. 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.
[edit] Indian Rhinoceros
The Indian Rhinoceros or the Great One-horned Rhinoceros (Rhinoceros unicornis) is now found almost exclusively in Nepal and North-Eastern India. 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 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.
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 2500–3200 kg (4,980–6,900 lb). Female Indian rhinos weigh about 1900 kg. The Indian Rhino is from 3-4 meters long. The record-sized specimen of this rhino was approximately 3800 kg. The Indian Rhino has a single horn that reaches a length of between 20 and 101 cm. Its size is comparable to that of the White Rhino in Africa.
Two-thirds of the world's Great One-horned Rhinoceroses are now confined to the Kaziranga National Park situated in the Golaghat district of Assam, India.[13]
[edit] Javan Rhinoceros
The Javan Rhinoceros (Rhinoceros sondaicus) is one of the rarest and most endangered large mammals anywhere in the world.[14] 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. 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.
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 (10-10.5 feet), including its head and a height of 1.5–1.7 m (4.9-5.6ft)tall. Adults are variously reported to weigh between 900–1,400 kg[15] or 1,360-2,000 kg.[16] Horns of males can reach 26 cm in length while in females they are knobs or no horn at all.[16]
