The rhinoceros, or rhino, is any of five surviving species of odd-toed ungulates in the family Rhinocerotidae. Two species are native to Africa and three to southern Asia. Four of the five species are critically endangered, and the other, the Indian Rhinoceros, is endangered.
The word "rhinoceros" is derived from the Greek words rhino,
meaning nose, and kera, meaning horn; hence "horned-nose". The
plural can be rhinoceros, rhinoceri, or rhinoceroses.
The family is characterized by large size (one of the few remaining megafauna surviving 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 its horn. The rhino is prized for its horn. Not a true horn, it is made of thickly matted hair that grows from the skull without skeletal support. Rhinoceros also have acute hearing and sense of smell, but poor eyesight over any distance. Most rhinoceros live to be about 50 years old or more. The collective noun for a group of rhinoceros is "crash".
Both African varieties have two horns in tandem while the Asian types have a single horn.
Several rhinoceros species became extinct within geologically recent times, notably the Giant Unicorn and the Woolly Rhinoceros in Eurasia; the extent to which climate change or human predation was responsible is debated. Current evidence indicates that they probably had survived many climate changes before modern man arrived.
Rhinoceros-like animals first appeared in the Eocene as rather slender animals, and by the late Miocene there were many species. Most were large. One, Indricotherium, may have weighed about 20 tons and (so far as is known) was the largest terrestrial mammal that ever lived. Rhinos in North America became locally extinct during the Pliocene, and in northern Asia, and Europe during the Pleistocene.
The five living species fall into three categories. 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. 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 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
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) because of their square lips. White Rhinoceros are
divided into Northern and Southern subspecies.
Interspecific hybridisation of Black and White Rhinoceros has also been confirmed.
This Rhinoceros Page is Copyright The Animal Web Guide © 2004 - 2009 Chuck Ayoub