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...