Rhinoceros

Rhinoceros, 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 2700 individuals remaining in the wild. The White is registered as Vulnerable, with roughly 14,500 remaining in the wild. The rhinoceros family is characterised by large size, one of the largest remaining megafauna alive today, with all of the species capable of reaching 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.

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. 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 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. The name White Rhinoceros was actually a mistake, or rather a corruption of the word wijd ("wide" in Afrikaans), referring to their square lips.

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). 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 Dvur 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.