Rhinoceros

Rhinoceros (pronounced /raɪˈnɒsərəs/), often colloquially abbreviated rhino, is a group of 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 greater, one-horned Indian Rhinoceros 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 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 (400–600 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.[3]

The rhino is killed by humans 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.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. The collective noun for a group of rhinoceros is crash or herd.[5]

Size comparison of extant rhinoceros species

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.
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White Rhinoceros

These White Rhinoceros are actually gray. The White in this species' name is from the Dutch word wijd which means wide. It refers to the White Rhinoceros's wide lip compared to the Black Rhinoceros's pointed lip. The original meaning was subsequently lost in translation.
Main article: 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 are thought to have become extinct in the wild.[9]. Six are known to be held in captivity, two of which reside in a zoo in San Diego. There are currently four that were in held in captivity since 1982 in a zoo in the Czech Republic which were transferred to a wildlife refuge in Kenya in December 2009, in an effort have the animals reproduce and save the subspecies[10].

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) The record-sized White Rhinoceros was about 4,600 kg (10,000 lb).[11] 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. 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. White rhinos aren't actually white, they are named after the Dutch word for wide.