The term "rhinoceros" is derived from two Greek words rhis meaning nose and keros meaning horn. Thus, the literally meaning of rhinoceros is "nose horn". It is said that rhinoceros
have been roaming on the earth for more than 60 million years.
Rhinoceros are the second heaviest ground living mammals.
They have been hunted for horns and skins which are believed
to have medicinal values. In India, rhinos are threatened by
poaching, habitat destruction and natural disaster.
Zoological name: There are five living species of rhinoceros. They include the great Indian one-horned rhinoceros (Rhinoceros unicornis), the Asiatic two-horned or Sumatran rhinoceros (Dicerorhinus sumatrensis), the lesser one-horned or Javan rhinoceros (Rhinoceros sondaicus), the square-lipped or the African white rhinoceros (Ceratotherium simum) and the hook-lipped or the African black rhinoceros (Diceros bicornis).
Distribution: The present day living species are found in Africa and southern parts of Asia. In India, they are restricted to Assam (mainly) and West Bengal. Habitat: Rhinoceros prefer to live in open grassland or forest interspersed with swamp, lake and marsh. The Indian rhinoceros prefers to live in forest mixed with swampy grassland.
Physical feature: Rhinoceros are characterized in having short and stout limbs and thick-skinned bodies. The body weight varies from 800 kg. (e.g. Sumatran rhinoceros) to 2500 kg (e.g. white rhinoceros) depending on species. The skull is broad at the base. Each foot is furnished with three toes with a hoof-like nail. The sole is tough and homey. The important anatomical feature is its horn or horns. The African species have two horns, while the Asian species with the exception of Sumatran rhinoceros have a single horn. The horns lack a bony core and are composed of collagen fibres. Both horns are located one behind the other in the middle line of the snout. The anterior horn is longer than the posterior one. The horn grows throughout the life and it begins to grow immediately once it is broken. The horn is loosely attached at its base. Females have smaller horns than males. The number of teeth varies from 24 to 30 depending on the species. Incisors and lower canine teeth are absent in the African species, while one or two upper incisors in each half of the jaw are present in the Asiatic species. The Javan and the Sumatran species have one canine tooth on each side of the lower jaw. Except the African white rhinoceros, all have a pointed upper lip. Like horse, they have a large caecum and colon. The gall bladder is absent like elephant. Asiatic rhinoceros (except Sumatran rhinoceros) have more folds of skin as compared to African rhinoceros.