Grévy's zebra

Grévy's zebra (Equus grevyi), also known commonly as the imperial zebra, is the largest living species of wild equid and the most threatened of the three species of zebras, the other two being the plains zebra and the mountain zebra. Named after French president Jules Grévy, it is found in parts of Kenya and Ethiopia. Superficially, Grévy's zebra's physical features can help to identify it from the other zebra species; its overall appearance is slightly closer to that of a mule and donkey, compared to the more "equine" (horse) appearance of the plains and mountain zebras. Compared to other zebra species, Grévy's zebra is the tallest; it has mule-like, larger ears, and has the tightest stripes of all zebras. It has a distinctively erect mane, and a more slender snout.

Grévy's zebra lives in semi-arid savanna, where it feeds on grasses, legumes, and browse, such as acacia; it can survive up to five days without water. It differs from the other zebra species in that it does not live in a harem, and it maintains few long-lasting social bonds. Stallion territoriality and mother–foal relationships form the basis of the social system of the Grévy's zebra. Despite a handful of zoos and animal parks around the world having had successful captive-breeding programs, in its native home this zebra is listed by the IUCN as endangered. Its population has declined from 15,000 to 2,000 since the 1970s. In 2016, the population was reported to be "stable"; however, as of 2020, the wild numbers are still estimated at only around 2,250 animals, in part due to anthrax outbreaks in eastern Africa.

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 Middle Pleistocene. Zebras appear to be a monophyletic lineage and recent (2013) phylogenies have placed Grévy'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.

Grévy's zebra is the largest of all wild equines. It is 2.5–2.75 m (8.2–9.0 ft) in head-body length, with a tail 55–75 cm (1.80–2.46 ft) long, stands 1.45–1.6 m (4.8–5.2 ft) high at the withers, and weighs 350–450 kg (770–990 lb). Grévy's zebra differs from the other two zebras in its more primitive characteristics. It is particularly mule-like in appearance; the head is large, long, and narrow with elongated nostril openings; the ears are very large, rounded, and conical, and the neck is short but thick. The muzzle is ash-grey to black in colour, and the lips are whiskered. 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, Grévy's zebra's pelage has a black and white striping pattern. The stripes are narrow and close-set, broader on the neck, and extending 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 Grévy's zebra. Foals are born with brown and white striping, with the brown stripes darkening as they grow older.

Grévy's zebra largely inhabits northern Kenya, with some isolated populations in Ethiopia. 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. Lactating mares and non-territorial stallions use areas with green, short grass and medium, dense bush more often than non-lactating mares and territorial stallions.

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. Mares require significantly more water when they are lactating. During droughts, the zebras will dig water holes and defend them.