Grevy's zebra

The Grévy's zebra (Equus grevyi), also known as the imperial zebra, is the largest living wild equid and the largest and most threatened of the three species of zebra, the other two being the plains zebra and the mountain zebra. Named after Jules Grévy, it is found in Kenya and Ethiopia. Compared with other zebras, it is tall, has large ears, and its stripes are narrower. The Grévy's zebra lives in semi-arid grasslands where it feeds on grasses, legumes, and browse; it can survive up to five days without water. It differs from the other zebra species in that it does not live in harems and has few long-lasting social bonds. Male territoriality and mother–foal relationships form the basis of the social system of the Grévy's zebra. This zebra is considered to be endangered. Its population has declined from 15,000 to 3,000 since the 1970s. However, as of 2008, the population is stable. The Grévy's zebra was first described by French naturalist Émile Oustalet in 1882. He named it after Jules Grévy, then president of France, who, in the 1880s, was given one by the government of Abyssinia. Traditionally, this species was classified in the subgenus Dolichohippus with plains zebra and mountain zebra in Hippotigris. Groves and Bell (2004) place all three species in the subgenus Hippotigris. Fossils of zebra-like equids have been found throughout Africa and Asia in the Pliocene and Pleistocene deposits. Notable examples include E. sanmeniensis from China, E. cautleyi from India, E. valeriani from central Asia and E. oldowayensis from East Africa. The latter, in particular is very similar to the Grévy's zebra and may have been its ancestor. The modern Grévy's zebra arose in the early Pleistocene. Zebras appear to be a monophyletic lineage and recent (2013) phylogenies have placed Grevy's zebra in a sister taxon with the plains zebra. In areas where Grévy's zebras are sympatric with plains zebras, the two may gather in same herds and fertile hybrids do occur. The Grévy's zebra is the largest of all wild equines. It is 2.5–2.75 m (8.2–9.0 ft) from head to tail with a 55–75 cm (22–30 in) tail, and stands 1.45–1.6 m (4.8–5.2 ft) high at the withers. These zebras weigh 350–450 kg (770–990 lb). Grévy's zebra differs from the other two zebras in its more primitive characteristics.:147 It is particularly mule-like in appearance; the head is large, long, and narrow with elongated nostril openings;:147 the ears are very large, rounded, and conical and the neck is short but thick. The zebra's muzzle is ash-grey to black in colour with the lips having whiskers. The mane is tall and erect; juveniles have a mane that extends to the length of the back and shortens as they reach adulthood. As with all zebra species, the Grevy's zebra's pelage has a black and white striping pattern. The stripes are narrow and close-set, being broader on the neck, and they extend to the hooves. The belly and the area around the base of the tail lack stripes and are just white in color, which is unique to the Grevy's zebra. Due to the stripes being closer together and thinner than most of the other zebras, it is easier for them to make a good escape and to hide from predators. Foals are born with brown and white striping, with the brown stripes darkening as they grow older. Embryological evidence has shown that the zebra's background colour is dark and the white is an addition. The stripes of the zebra may serve to make it look bigger than it actually is or disrupt its outline. It appears that a stationary zebra can be inconspicuous at night or in shade. Experiments have suggested that the stripes polarize light in such a way that it discourages biting horse-flies in a manner not shown with other coat patterns. Other studies suggest that, when moving, the stripes may confuse observers, such as mammalian predators and biting insects, via two visual illusions, the wagon wheel effect, where the perceived motion is inverted, and the barber pole illusion, where the perceived motion is in a wrong direction. The Grévy’s zebra largely inhabits northern Kenya, with some isolated populations in Ethiopia.:147 It was extirpated from Somalia and Djibouti and its status in South Sudan is uncertain. It lives in Acacia-Commiphora bushlands and barren plains. Ecologically, this species is intermediate between the arid-living African wild ass and the water-dependent plains zebra.:147 Lactating females and non-territorial males use areas with green, short grass and medium, dense bush more often than non-lactating females and territorial males. Grévy's zebras rely on grasses, legumes, and browse for nutrition. They commonly browse when grasses are not plentiful. Their hindgut fermentation digestive system allows them to subsist on diets of lower nutritional quality than that necessary for ruminant herbivores. Grevy's zebras can survive up to a week without water, but will drink daily when it is plentiful. They often migrate to better watered highlands during the dry season. Females require significantly more water when they are lactating. During droughts, the zebras will dig water holes and defend them. The grévy's zebras main predator is the lion, but adults can be hunted by spotted hyenas. African hunting dogs, cheetahs and leopards almost never attack adults, even in desperate times, but sometimes prey on young animals, although females are fiercely protective of their young. In addition, they are susceptible to various gastro-intestinal parasites, notably of the genus Trichostrongylus.