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You are here: Home > Wildlife > Mammals > Grevy's zebra
WILDLIFE: MAMMALS: GREVY'S ZEBRA

Class: Mammals
Order: Perissodactyls
Family: Equids
Genus and species: Equus grevyi
Common name:
English: Grevy's zebra
Swahili: Kangaja
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Identification
Body: the silhouette of Grevy's zebra recalls an ass or a mule, contrary to the plains zebra that resembles a pony. Background colour white or cream. Stripes black or dark brown, very numerous, narrow and vertical. Belly unstriped, white in colour. Mane thick and high that reaches the withers. Broad dorsal stripe from half back to tail, separated from the rump stripes by a white area. In rump and tail base, stripes are narrower and concave upwards, forming a "target". Stripes are broader in neck and chest. Legs completely striped with a transversal pattern. Height at shoulder: 1.5 m. Length: 2.5 m. Tail: 70 cm. Weight: males 380-450 kg, females 350-450 kg. The largest of all zebras. The foal's stripes are brown reddish.
Head: long and narrow, especially the muzzle, which has a brown spot separated from the striped pattern by a white area. Large rounded ears, with a black edge and a white tip. The inner margin is framed by a hairy fringe.
Distribution and ecology
Distributed throughout North Kenya, from Tana river northwards, and northwestwards to the eastern shore of Lake Turkana. It is found exclusively in this region of Kenya and in southern Ethiopia, with only a few thousands surviving today. Occupies the intermediate niche between the plains zebra, more water-dependent, and the wild ass, more desert-adapted. Inhabits open dry plains and arid scrubland. Associates with plains zebras in mixed herds, in which Grevy's outnumber their partners. However, both species do not interbreed in the wild.
Food
Grazes all types of grass, even of the kind that is too coarse for cattle. It also browses leaves, especially in the dry season. It is less dependent on water than plains zebra; drinks daily if there is water available, but if necessary, it can resist two or three days without liquid. During prolonged drought, it can dig the dry river beds searching for subterranean streams.
Behaviour
Diurnal and nocturnal. Grevy's social behaviour is completely different from plains zebras. Their sociability is similar; however, Grevy's zebra is territorial and builds open, non-cohesive groups. Contrary to the plains zebra, grooming is almost absent.
The basic social unit is a female with her 1-2 younger foals. These families combine in groups of 5-10 females with their offspring, but they are unstable unions, without cohesion or rank hierarchies. Groups may associate with plains zebras and several antelope species, and during the dry season they can aggregate in mixed herds of 100-200 head, sometimes reaching 450. These herds migrate in the dry season in search of rich water and pasture areas, but afterwards they disperse to avoid competing for the scarce grass.
Adult males are solitary and territorial. Generally they dominate an area of 6 km², bordered by topographic accidents such as stream beds. Stallions signpost their domains with urine and dung piles, apart from raising awareness with their physical presence and their call, a blend of an ass's bray and a hippopotamus's growl. In many cases and if conditions of water and food are favourable, territorial males will remain in their domains all year round without joining the migrations, thus awaiting for the return of females with the onset of rains, when the peak breeding season begins. Neighbouring territorial males frequently socialize at the boundaries through a series of rituals, and combats may sometimes break out, in which males neck-wrestle, bite each other and exchange kicks.
The groups of mares usually roam through overlapping territories, covering each day a distance of 10-15 km that comprises the domains of several territorial males. At the age of 3, young males leave their mothers to gather in bachelor groups of 2-6, maximum 10. These groups can be allowed by territorial stallions into their domains, and they may even mix up with female groups in search of pasture, but only as long as mares are not in heat. If estrous females are present, the adult stallion will never tolerate an invasion by another territorial male, but it may grant the presence of bachelor groups within its territory as long as they keep at a reasonable distance from estrous mares. At the age of 6, young bachelors can demarcate their own territory.
The primary predator of Grevy's zebra is the lion, that preys both on adults and foals. The latter are threatened as well by leopards and hyenas. During drought, when females are bound to walk great distances in search of water, they often leave foals unattended. The youngs lack concealment instinct and thus become easy prey for carnivores. The longevity of Grevy's zebras is 15-20 years.
It is remarkable that, regardless of the stripes and the name of "zebra" shared by both, actually Grevy's and plains zebras are not more closely related than each of them is with horses or asses. This is also shown by their different social organizations, which respond to adaptations to diverse habitats. Plains zebras are basically nomadic and non-territorial, hence stallions find it convenient to join the groups of mares and follow them along their movements to ensure reproduction. Instead, Grevy's are territorial despite their migrations, so males can establish their domains and thus gain access to females in transit through their territory.
Reproduction
Mares start breeding at the age of 3. Most births occur in the wet season, but procreation takes place all year round. Gestation is 12-13 months. The only foal born is able to stand on its legs several minutes after birth, and one hour later it starts trotting, though its legs are so long that it has to split them apart to reach the ground with the nose. Within the great herds, mares with young foals gather in nursing groups, sometimes together with heavily pregnant females and mothers with older foals.
Related species
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