Zebras

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Zebras

Zebras are members of the horse family (Equidae) that inhabit tropical grasslands (savannas) in much of sub Saharan Africa. Three of the seven species of equids are zebras. Zebras are herd-living, social ungulates (hoofed mammals) recognized by a black-and-white (or cream or yellowish) striped coat, short erect mane, and a tail averaging about 18 in (0.5 m) long. The body length of a zebra is about 6-8.5 ft (2-2.6 m) long, and body weight can reach 770 lb (350 kg), with males slightly bigger than females.

There are three species and several subspecies of zebra. The common, Burchell’s, or plains zebra (E. burchelli) lives throughout much of eastern and southern Africa, and is the best-studied species. Grevy’s zebra (Equus grevyi) is found in Somalia, Kenya, and Ethiopia, and is the largest of the wild horses, characterized by large ears, narrow stripes, and a thick neck. The third species is the mountain zebra (E. zebra) found in the hill country of Angola, Namibia, and western South Africa.

The stripes of the zebra camouflage the animal in the waving grasses of the African grasslands, especially at dusk and dawn. Zebras rest in herds in open ground where they can see predators approaching, rather than lying down in the grass. When a herd of zebras is being chased by predators such as lions or hyenas, their stripes make it difficult for predators to visually latch on to a specific animal to attack. Other suggestions are that the stripes identify individual zebras as part of a group and also initiates mating behavior.

The common zebra

The common or Burchell’s zebra stands about 50-52 in (1.3 m) tall at the shoulder. It has the widest stripes of all zebras, and the stripes continue down to the belly of the animal. The stripes of Burchell’s zebra become fainter and almost disappear in southern populations.

There are several subspecies of the common zebra, distinguishable by the pattern of stripes on the rump. Grant’s zebra (E. burchelli granti) has wide rump stripes, the Chapmann’s or Damaraland zebra has tan shadow stripes between the black stripes, and Selous’s zebra has only faint shadow stripes between the black stripes. A subspecies known as the “true” Burchelli’s zebra had reddish brown stripes, and became extinct in the early 1900s.

Herds of common plains zebras are actually a collection of family groups. Each family group is headed by a dominant male stallion, and one female is dominant over the other seven or eight females and their young. When the group is feeding or drinking, one animal stands guard. If a predator approaches, such as a troop of wild dogs or lions, the stallion zebra moves to the back of the fleeing herd and ensures that no single animal falls behind or gets separated and becomes vulnerable to attack. Zebras that become isolated call attention to their plight by making a harsh sound like a combination bark and bray, which draws the other zebras back to protect it.

The zebra’s large, rounded ears turn in every direction and are able to pick up the slightest sound. The zebra’s primary defense is running, which it can do at speeds approaching 40 mph (64 kph), though for only a short time. Given the chance, a zebra fights primarily by kicking with its hind hooves. However, an attacking predator is likely to grasp the animal’s neck with one quick leap that prevents the zebra from acting.

After a young mare mates for the first time, she will stay with the same family group for the rest of her life. Males that have not yet developed herds—or that have been ousted from their herds by other males— live in male-only bands (bachelor herds), which they leave to find mates at about six years old. If stallions try to take mares from an existing family group, they will have to fight that group’s stallion.

Gestation lasts approximately one year, with only one off spring produced. The young are born with disproportionately long legs and are ready to run with the herd within a few minutes. The brown-striped coat of a new foal gradually changes to the familiar black and white.

Mountain zebras

There are two subspecies of mountain zebras in South Africa which live on rough, rocky highlands, but once also occurred in large numbers in the grassy lowland plains. The Cape mountain zebra of South Africa is the smallest zebra, standing about 4 ft (1.2 m) at the shoulder and weighing about 600 lb (272 kg). The stripes of the Cape mountain zebra are slightly wider and shorter than those of the other subspecies, Hartmann’s mountain zebra of Namibia. The Cape mountain zebra has a dewlap under the lower jaw, which other zebras do not have.

Herds of the common zebra readily mix with herds of wildebeest, but Cape mountain zebras tend to keep apart from other animals. Hartmann’s zebras have the ability to locate water in apparently dry valleys.

Grevy’s zebra

Grevy’s zebra is quite different in both appearance and behavior from the common zebra. It stands about 5 ft (1.5 m) tall at the shoulder and weighs about 990 lb (450 kg). Its stripes are very narrow, do not cross over the lower back as they do in the Cape mountain zebra.

Grevy’s zebras live in semidesert country and do not form herds. Instead, only the mother and foals remain together, while the males and the young females drift off. Individual stallions have remarkably large breeding territories, and any female found within the territory belongs to the male. A stallion will tolerate other males in his territory only if they do not try to mate with the mares. The gestation period of the Grevy’s zebra is about 13 months, one month longer than other species of zebra.

The recently extinct zebra-like quagga (E. quagga) looked like a combination of wild ass and zebra and had a reddish coat and stripes only on the head, neck, and shoulders. The name quagga is derived from the odd bray of this species, which was described as “kwa-ha.” The quagga lived throughout South Africa but was killed by nineteenth-century settlers for its meat and hides. The last quagga died in an Amsterdam zoo in 1883.

KEY TERMS

Dewlap —A loose fold of skin that hangs from the neck.

Equid —Any member of family Equidae, including horses, zebras, and asses.

Gestation —The period of carrying developing off spring in the uterus after conception; pregnancy.

The populations of the common zebra are high, especially in the Serengeti Plains of Tanzania and Kenya, where zebras run with the huge wildebeest herds on their annual migrations.

Grevy’s zebra and the Cape mountain zebra are both endangered. As of 2003, there were from 3,000 to 3,500 Grevy’s zebras in Ethiopia, Somalia, and Kenya, in three separate populations. A major herd of Grevy’s zebra is protected in a game reserve in Kenya. There are about 1,200 Cape mountain zebras, most of which live in Mountain Zebra National Park in South Africa.