Popularly called rhinos, rhinoceroses are heavily-built, thick-skinned herbivores with one or two horns on their snout and three toes on their feet. The family Rhinocerotidae includes five species found in Asia and Africa, all of which face extinction .
The two-ton, one-horned Great Indian rhinoceroses (Rhinoceros unicornis ) are shy and inoffensive animals that seldom act aggressively. These rhinos were once abundant in Pakistan, northern India, Nepal, Bangladesh, and Bhutan. Today, there are about 2,400 Great Indian rhinos left in two game reserves in Assam, India, and in Nepal. The smaller one-horned Javan rhinoceros (Rhinoceros sondaicus ) is the only species in which the females are hornless. Once ranging throughout southeast Asia, Javan rhinos are now on the verge of extinction, with only 60 living on reserves in Java and Vietnam.
The Sumatran rhinoceros (Didermocerus sumatrensis ), the smallest of the rhino family, has two horns and a hairy hide. There are two subspecies—D. s. sumatrensis (found in Sumatra and Borneo) and D. s. lasiotis —found in Thailand, Malaysia, and Burma. Sumatran rhinos are found in hilly jungle terrain and once coexisted in southeast Asia with Javan rhinos. Now there are only 300 Sumatran rhinos left.
The two-horned, white, or square-lipped, rhinoceros (Ceratotherium simum ) of the African savanna is the largest land mammal after the African elephant, standing 7 ft (2 m) at the shoulder and weighing more than 3 tons. White rhinos have a wide upper lip for grazing. There are two subspecies: the northern white (C. s. cottoni ) and the southern white (C. s. simum ). Once common in the Sudan, Uganda, and Zaire, northern white rhinos are now extremely rare, with only 40 left (28 in Zaire, the rest in zoos). Southern African white rhinos are faring somewhat better (7,500) and are the world's most common rhino.
The smaller two-horned black rhinoceros (Diceros bicornis ) has a pointed upper lip for feeding on leaves and twigs. Black rhinos can be aggressive but their poor eyesight makes for blundering charges. Black rhinos (which are actually dark brown) were once common throughout sub-Saharan Africa but are now found only in Kenya, Zimbabwe, Namibia, and South Africa. Today, there are only 2,600 black rhinos left in the wild, compared to 100,000 30 years ago.
Widespread poaching has diminished rhino populations. The animals are slaughtered for their horns, which are made of hardened, compressed hair-like fibers. In Asia, the horn is prized for its supposed medicinal properties, and powdered horn brings $28,000 per kg. In Yemen, a dagger handle made of rhino horn can command more than $1,000. As a result, rhinos now survive only where there is strict protection from poachers. Captive breeding programs for endangered rhinos are hindered by the general lack of breeding success for most species in zoos and a painfully slow reproduction rate of only one calf every three to five years. The present world rhino population of about 16,000 is little more than half the estimated "safe" long-term survival number of 22,500.
[Neil Cumberlidge Ph.D. ]
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