Rhinoceros commonly known as rhino is represented by five species living today. They belong to the family of odd-toed ungulates known as Rhinocerotidae. Two species are native to Africa and three to southern Asia. The family Rhinocerotidae is characterized by its large sized individuals all reaching the body weight of about 1 tonne and herbivorous habit. They are protected by a tough skin coat about 1-1.5 cm thick and is made up of layers of collagen positioned in lattice structure. The brain is relatively small in size as compared to other mammals and bears a tough horn. They prefer to feed on leafy material and are also able to ferment food in their hindgut so can subsist on more fibrous plant material, if required. African species of rhinoceros lack teeth in front of their mouth but possess well developed premolars and molars for grinding the plant material. They are hunted by humans for their precious horns which are made up of keratin. The hairs and fingernails are also made up of keratin. Both species of African and Sumatran Rhinoceros have two horns while the Indian and the Javan Rhinoceros have one horn only. They bear poor eyesight but have acute sense of smell and sense of hearing. Average lifespan is about 60 years or more. The IUCN Red List marks three species to be critically agreed.
The rhino derives its name from a Greek word. They are supposedly to have evolved during the Pliocene and the Miocene Period. The White Rhinoceros is the most massive land animal just after the elephant living present. The Indian Rhinoceros and the hippopotamus come next to it. There are two subspecies of the White Rhinoceros which are the Southern and Northern White Rhinoceros. The population of the Southern White Rhinos is about 14,500. White Rhinos have broad head, massive body, short neck and broad chest. The body weight may exceed to about 3,500 kilograms. The snout is demarcated by the presence of two horns of which the front one is larger reaching a length of 90-150 cm. They also bear a prominent muscular hump that supports the massive head. The body coloring may include the shades of yellowish brown to slate gray. Majority of the hairs are found on the ear fringes and the tail bristles. The mouth is flat and broad suitably adapted for grazing.
The Black Rhinoceros is named just to distinguish it from the White Rhinoceros but this may be quite confusing as both the species can not be identified on the basis of body color. An adult Black Rhinoceros measures 150-170 cm high at the shoulder and 3.5-3.9 m in length. Adult weighs about 850-1,600 kg and the females are smaller than the males. There are two horns on the skull with the front one larger reaching a length of 50-140 cm and both the horns are made up of keratin. Sometimes a smaller third horn may also develop. They are smaller than the White Rhinos and bear pointed mouth which is used for grasping leaves and twigs during feeding. The Indian Rhinoceros or the Great One-Horned Rhinoceros is now exclusively found in Nepal and North Eastern India. Earlier they were also reported from Pakistan, Burma and also roamed to China. But due to human interference they are now confined to the tall grasslands and forests in the foothills of Himalayas. The color of the body is silvery brown which forms huge folds all over the body. The upper legs and shoulders are covered in wart-like bumps with very little body hair. The full grown males are larger than the females weighing about 2,500-3,200 kg. The Indian Rhino stands 1.75-2 meters. Females weigh about 1,900 kg. They have a single horn reaching a length of 20-100 cm. Body size is comparable to the White African Rhino. Two third populations of the Great One Horned Rhinoceros are bound to the Kaziranga National Park located in the Golaghat district of Assam, India.
The Javan Rhinoceros is one of the rarest and most endangered species of large mammals found all over the world. According to an estimate of 2002 only 60 individuals are present in Indonesia and Vietnam. They prefer to inhabit low low rainforest, tall grass and reed beds that are plentiful with large food plains and mud wallows. They were large hunted for the medicinal powers of the horns and the blood. They are on the verge of extinction. At present only 40 individuals are present in the Ujung Kulon Conservation, Java, Indonesia. Like the Indian Rhino it also bears one horn and the skin is present in the form of folds over the shoulder, back and rump giving an armored appearance to the body. The body is 1.5-1.7 m tall. Adults weigh about 900-1,400 kg. Females either lack horn or may bear tiny knobs but in male the horn may be about 26 cm in length.
The Sumatran Rhinoceros is the smallest among all the species of Rhinos present today. Their skin is well adapted to survive at high altitudes of Sumatra and Borneo. Due to habitat destruction and poaching this is one of the rarest mammals of the world. Only 275 individuals are alive in the present scenario. The body attains a length of 240-315 cm and body weight of around 700 kg. Like the African species it also bears two horns the front one is larger and the other one is smaller measuring less than 10 cm in length. Males have larger horns than the females. Hairs are weak in the young ones but they become scarce in the adults. The body color is reddish brown and the body is short with stubby legs. Lips are prehensile. Rhinos have very few natural predators apart from humans. Young ones easily fall in the hands of big cats, crocodiles, hyenas and wild dogs. It is also well known that the Nile crocodile preys on the Black Rhino.
Rhino horn is made up of keratin and lacks bony core. The horns were used in the traditional Asian medicine for the dagger handlers in Yemen and Oman. Horns were also a part of traditional Chinese medicine and were used for the treatment of fever and convulsions. There are legends about rhinos stamping out fire in India, Burma and Malaysia.