zebra, herbivorous hoofed African mammal of the genus Equus, which also includes the horse and the ass. It is distinguished by its striking pattern of black or dark brown stripes alternating with white. In size and body form it is intermediate between the larger horse and the smaller ass. It has a heavy head, stout body, short, stiff mane, and tufted tail. There are three living zebra species; a fourth species, the quagga, became extinct in the late 19th cent. Most zebras inhabit open plains or brush country, while mountain zebras favor rocky hillsides. Zebra herds on the Serengeti of E Africa can be as large as 200,000 individuals, but all are organized in family groups led by a stallion. The plains zebras usually mix with other grazing animals, such as wildebeest and antelopes. They are swift runners, achieving speeds of up to 40 mph. Some authorities believe that the stripes evolved as visual identification to reinforce social bonds with other zebras, rather than for disguise or insect protection. The zebra's natural enemies are the lion and the leopard. The plains zebra, Equus burchelli, is found throughout Africa S of the Sahara. It stands about 4 ft (120 cm) tall at the shoulder and has small ears. It has very broad stripes, which vary greatly in their pattern among the several races of the species, as well as among individuals of the same race. Grevy's zebra, E. grevyii, is a large zebra found in E Africa. It stands 41/2 to 5 ft (140–150 cm) at the shoulder and weighs about 600 lb (270 kg). It has large, rounded ears and numerous very narrow stripes. Most distinctive is the mountain zebra, E. zebra, with a donkeylike build, long ears, and a characteristic stripe pattern. Unlike any other member of the genus Equus, its throat has a dewlap. One race of the mountain species, Hartmann's zebra, found in the arid mountains and coastal plains of SW Africa, increased in numbers in the 1980s to an estimated 15,000 from about 7,000 in 1967. The other race, the endangered Cape mountain zebra, is rarely found outside a protected area in South Africa. Zebras have been hunted extensively for their flesh and skins, but the plains zebra and Grevy's zebra are still numerous. Zebras have been crossed with horses in an attempt to produce a draft animal, but the offspring have proved sterile and unreliable. Zebras are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Perissodactyla, family Equidae.