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Two of the five rhinoceros species are African and three Asian. The African species have two horns, one behind the other, and their skins are gray and smooth rather than folded. The black rhinoceros, Diceros bicornis, of E and S Africa, has declined in numbers from 65,000 in 1970 to about 2,600 in 1996; there were 2 to 3 million at the beginning of the 20th cent. It has a grasping upper lip, used for browsing shrubbery. Its front horn may be over 18 in. (45 cm) long. Unpredictable and sometimes dangerous, it can turn and charge with great force if irritated. The white, or square-lipped, rhinoceros, Ceratotherium simum, is divided into two subspecies: the northern white rhinoceros, which survives in the wild only in the Garamba National Park in the Congo, and the southern white rhinoceros, which is found primarily in South Africa; the term white may be a corruption of the Afrikaans word for "wide," referring to its broad snout. The white rhinoceros is second in size among land mammals to the elephant. It stands 6 1/2 ft (2 m) at the shoulder, is 13 ft (4 m) long, and weighs 3 to 4 tons (2,700–3,600 kg). More than half of the world's estimated 13,600 remaining rhinoceroses are of the southern white subspecies. The estimated 30 surviving northern white rhinoceroses are protected by armed guards.
Two of the Asian species have a single horn. The Indian rhinoceros, Rhinoceros unicornis, is the second largest rhinoceros and can weigh over 2 tons (1,820 kg). Its thick hide is deeply creased in places, creating the impression of armor plates; folds of thinner skin allow body movement and flexibility. Indian rhinos have reached speeds of 30 mph (48 kph) in charges. Perhaps 2,000 live on the grassy plains of Bengal, Assam, and Nepal, some of them in groups. Their population hit a low point in 1970 at 900. The solitary and smaller Javan rhinoceros, R. sondaicus, is nearly extinct. The Sumatran rhinoceros, Dicerorhinus sumatrensis, also critically endangered, is the only rhinoceros with a hairy coat and the only Asian species with two horns. Smallest of the rhinoceroses, it stands 4 1/2 ft (1.4 m) and weighs about 1 ton (900 kg). Fewer than 400 survive in remote forests of Sumatra, the Malay Peninsula, and Borneo.
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