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.

Taxonomy and naming

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.

Fossils of zebra-like equids have been found throughout Africa and Asia in the Pliocene and Pleistocene deposits. The latter, in particular is very similar to the Grévy's zebra and may have been its ancestor. 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.

Description

thumb|left|From left to right: a cranium, a complete skeleton, a left forefoot frontal, and a left forefoot lateral from a Grévy's zebra

Grévy's zebra is the largest of all wild equines. It is in head-body length, with a tail long, stands high at the withers, and weighs . 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; It lives in Acacia-Commiphora bushlands and barren plains.

Grévy's zebras rely on grasses, forbs (such as 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.

Behaviour and life history

thumb|right|Herd of Grévy's zebras

Adult stallions mostly live in territories during the wet seasons but some may stay in them year round if there's enough water left. An oestrous mare may visit as many as four territories a day

thumb|right|Zebra mare near younger zebras

The resident stallions of territories will try to subdue the entering mares with dominance rituals and then continue with courtship and copulation. This is a useful adaptation for a species whose mares mate polyandrously. Bachelors or outside territorial stallions sometimes "sneak" copulation of mares in another stallion's territory.

thumb|Grévy's × plains zebra hybrid, alongside plains zebras

Gestation of the Grévy's zebra normally lasts 390 days (13 months), The foals will not hide, so they can be vulnerable to predators. To adapt to a semi-arid environment, Grévy's zebra foals have longer nursing intervals and wait until they are three months old before they start drinking water. Although offspring become less dependent on their mothers after half a year, associations with them continue for up to three years.

At least one specimen of the rare animal was imported into Rye, New York in the United States by Warner M. van Norden and his wife Grace Talcott as part of an endeavor to hybridize the animal with horses to create a superior farm animal. A special "zebra house" was built for the red-striped animal and other zebras complete with steam heating. Four of the specimens are said to have been kept on the Jay Estate for a number of years.

Status and conservation

thumb|left|Grevy's zebras in [[Samburu National Reserve]]

The Grévy's zebra is considered endangered. In 2008, it was estimated that there are less than 2,500 Grévy's zebras still living in the wild, further declining to fewer than 2,000 mature individuals in 2016. Nonetheless, the Grévy's zebra population trend was considered stable as of 2016.

The Grévy's zebra is legally protected in Ethiopia. In Kenya, it is protected by the hunting ban of 1977. In the past, Grévy's zebras were threatened mainly by hunting for their skins which fetched a high price on the world market. However, hunting has declined and the main threat to the zebra is habitat loss and competition with livestock. Cattle gather around watering holes and the Grévy's zebras are fenced from those areas.

References

  • "Wildlife Grévy's Zebra" – summary from the African Wildlife Foundation
  • Images and footage of Grévy's zebra from ARKive.org
  • "To Catch a Zebra" by Brian Jackman – story of catching endangered Grévy's zebra for relocation
  • "Why are the Grevy's Zebras in Trouble?" – Rich Blundell reports from Kenya
  • Grevy's Zebra Trust – a Kenyan organization dedicated to preserving the Grévy's zebra