Grevy's Zebra
Equus grevyi
The Grévy’s zebra belongs to the Equidae family, which includes thehorses and donkeys as well as the plains and mountain zebras. The Grévy’s zebra – the first of the zebras to evolve – staked its primary range out of sparse plains and scrublands in the Horn of Africa. Ithas developed finely tuned adaptations to its arid home.
Characteristics
The Grévy’s, roughly 25 to 35 percent larger than the plains and mountain species, is one of the odd-toed ungulates—the large grazing and browsing mammals that have an odd number of weight-bearing toes, or hoofs (actually modified toenails), on each foot. Like the horses, donkeys and other zebras, the Grévy’s has a single weight-bearing hoof on each foot.
- Size and Weight: Shoulder height, about four to five feet high; length (nose tip to tail base), eight to ten feet; weight, male, about 1000 pounds maximum and female, about 900 pounds maximum.
- Body: Stocky and muscular.
- Head: Large, long and narrow, with large ears rounded at tips.
- Mane: Naturally cropped and erect, mohawk-like appearance.
- Legs: Lithe and lean, with the hard hooves suited for rough terrain.
- Tail: One and one-half to two and one-half feet in length, tufted at tip.
- Stripes: Black (or dark brown) and white (or buff), vertical and narrowly set from the face to the hind quarters; generally transverse and broader on the hind quarters and legs; single dark stripe along the spine and tail; stripes absent on the light-colored belly and between the hind quarters.
- Senses: Acute day-and-night, binocular, probably color vision; keen hearing; highly perceptive taste.
- Teeth and Digestive System: Matching incisors designed for cropping coarse grasses; sturdy molars designed for grinding the grasses; single stomach and hind-gut fermentation system that facilitates digestion of grasses that other hoofed herbivores cannot digest.
Range and Diet
The Grévy’s zebra ranges across the hot and arid plains and scrublands of northeastern Kenya and southeastern Ethiopia. It grazes on the coarse grasses for its primary food, but during dry periods, it may also browse on shrub leaves, bark and roots. It must spend much of its time, day and night, feeding--consuming the large volumes it requires to meet its dietary requirements from nutritionally impoverished food sources. If water is available, it will drink daily. If water is not readily available, however, the Grévy’s can survive for two or three days without drinking. During severe drought, it may dig with its front hoofs in dry river beds to uncover subterranean streams.
By contrast, the plains zebra grazes and browses on the more lush plains and grasslands that run from the Horn of Africa southward along the eastern side of the continent, migrating as much as 700 miles to maintain ready access to water. In some areas, its range overlaps that of the Grévy’s zebra. The Mountain Zebra ranges across the arid stony slopes of hills and mountains in southern Africa, grazing and browsing on grasses, shrubs and roots. During drought, it may also resort to digging with its front hoofs in dry river beds to reach water.
Behavior and Life Cycle
For much of the year, the Grévy’s zebra maintains a relatively dispersed social network--a behavioral adaptation that helps reduce competition for the limited resources in its arid plains and scrublands. For much of the year, the male lives a basically solitary life primarily within a three- to four-square-mile territory, marking the boundaries with urine and dung and proclaiming his ownership through a kind of braying growl. Given sufficient water and feed, a male may remain in his territory throughout the year. The female, with one or two foals, may join loose-knit groups of other females with foals, sometimes mixing with plains zebras and other grazing and browsing animals.
During dry periods, the Grévy’s zebra – males and females – may congregate in loosely organized herds of several hundred to migrate to more rewarding pasturage, where they will scatter to minimize competition for sparse grass. During the wetter seasons, as herds begin to retrace migratory routes, the male capitalizes on opportunities to mate with estrous mares passing through his territory. He might go to combat – raring, kicking and biting savagely – with any other male that chances to enter his territory to compete for breeding rights.
About a year after breeding, the female delivers a single foal, which finds its legs within an hour of its birth. At first, she is intensely possessive of her newborn, which may otherwise wander away and follow another female. Once her maternal relationship becomes firmly set, she may leave her foal unattended – and more vulnerable to predation – when she has to travel some distance to reach water. She will nurse her foal for some months, although it starts to graze within several weeks after its birth. She may keep her offspring nearby for the first three years of its life.
At about three years of age, the male declares his independence and joins a small bachelor group. At about six years of age, it reaches sexual maturity. It establishes a territory, ready to begin breeding. At about two years of age, the female attains sexual maturity, and at about three years of age, she may join ever changing herds or harems and begin foaling.
In the wild, the Grévy’s zebra typically lives for 15 or 20 years, and in captivity, for 40 years!
Perils
The Grévy’s zebra, particularly a young foal, suffers predation by a number of the meat eaters, including lions and hyenas and, to a lesser extent, cheetahs, leopards and wild dogs. It suffers more, however, at the hands of man, who hunts the Grévy’s for its elegantly striped and valuable hide and who co-opts the zebra’s pasturage and waterholes for domestic livestock. Listed as threatened by the World Conservation Union, the Grévy’s zebra now numbers no more than perhaps 1,500 to 2,000 in the wild--a decline of 85 to 90 percent within the past several decades.
Interesting Facts
- The Grévy’s was named for François Paul Jules Grévy (President of the Republic of France from 1870 to 1887), who owned one of the zebras.
- As with the other zebras, the Grévy’s stripes serve as an effective camouflage, effectively blending in with the vertical lines of the grasses around it, confusing predators, which are color blind.
- In flight, the Grévy’s stripes effectively create a shimmering and swiftly changing optical illusion, complicating the meat eater’s efforts to single out its prey.
- The zebra has an extra layer of fat beneath each of its dark stripes, making the tissue several degrees Fahrenheit hotter than that beneath the white or cream-colored stripes.
- Like the other zebras, each Grévy’s has a unique stripe pattern, which, like a fingerprint, identifies the individual.
- Like other members of the Equidae family, the Grévy’s foot -- with only the hoof touching the ground and other parts having evolved into essentially leg parts -- serve to increase the length and rate of stride, making it possible for the animal to run 40 miles an hour and outdistance many predators.
- Although the Grévy’s and plains zebras both have stripes and share a common name, they are no more closely related to each other than they are to a horse or a donkey.
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