Grevy’s Zebra, Equus grevyi
Grevy’s Zebra (Equus grevyi) is the largest wild equid in existence today. It is also known as the imperial zebra. It is the most endangered of all species of zebra. Named after Jules Grevy, this zebra can be found in Ethiopia, but mainly in Kenya. At one time, Grevy’s zebra roamed Eritrea, Somalia, Kenya, and Ethiopia, but its populations have dwindled and now reside in small areas in northern Kenya, and a few small areas in Ethiopia.
In 1882, a French naturalist named Émile Oustalet described Grevy’s zebra, naming it after the president of France during that time, who had been given one of the zebras by the Abyssinia government. Grevy’s zebra is the only living species in the subgenus Dolichohippus, as the plains zebra and mountain zebra are in the Hippotigris subgenus.
Many fossils have been found of Dolichohippus, including E. cautleyi from India, E. sanmeniensis from China, E. valeriani from central Asia, and E. oldowayensis from East Africa. The individual from East Africa is similar to Grevy’s zebra, and may be an ancestor of it. Through phylogenetic research, it was found that Grevy’s zebra, which first appeared in the Pleistocene era, is more appropriately grouped with asses and wild donkeys rather than with plains zebras, but it is not completely separate from mountain zebras. In areas where Grevy’s zebras and plains zebras merge, they can be seen grazing together and will even produce fertile hybrids.
With a body length of up to nine feet, Grevy’s zebra is the largest of all wild equines and can weigh up to 990 pounds. Grevy’s zebra sare distinctive from other zebra species in that their characteristics are more primitive. The large head and narrow muzzle, along with the thick neck, all show this zebra’s primitive features. The coat of the Grevy’s zebra is typical to all zebra species, with black white stripes. The stripes are mainly thin and close together, but they become thicker at the neck. The underbelly and base of the tail do not have these stripes, and young zebras are born with brown stripes that turn to black as they age. It is thought that these stripes serve as a means of confusing potential predators and the stripes allow the zebra to camouflage well at night. The mane of an adult Grevy’s zebra is erect and is not as long as the mane on young zebras.
Grevy’s zebra do not form the same social structures as other zebras, preferring to construct an equal herd of females and young with no hierarchy. Adult males are territorial, and will create a territory of up to 3.5 miles, using dung piles and vocalizations. Typically, males will remain in their territories during the wet season, but if water is plentiful, they will remain year-round. Males that do not have territory are known as bachelors. Females, their young and, non-territorial males roam through a wide range, and females prefer areas with abundant food and water resources.
Territorial males will allow strange males to enter their territory without question, unless a female in estrous is near and up to nine males may compete for a female outside of their territories. It is thought that some non-territorial males avoid areas that belong to other males in order to avoid that conflict. Stallions will often group together when females are not around. When exercising dominance, a Grevy’s zebra will arch its neck and walk with a high-stepping gait, leaving the submissive zebra to extend its tail and nuzzle the dominant zebra’s groin or chest.
Mating season for the Grevy’s zebra occurs mainly during the rainy seasons, but they are able to mate throughout the year. Typically, most births occur through the months of August or September. Most female, or mares, will wander through four territories a day seeking a male to mate with, and the most dominant males occur in areas where water is abundant attracting mares with foals. Males who control territories with more vegetation attract mares that are not lactating, and therefore, need less water than mares with foal.
Male Grevy’s zebra will perform dominance rituals once a female enters its territory and will then continue with courtship rituals that conclude with mating. Stallions are able to emit large amounts of semen that will overtake that of other zebras that the female may have mated with, and it is not uncommon for males without territories to “sneak” in and mate with females located within those territories. Although mares do not mate with a single stallion, they have been known to remain with one male for a period after giving birth. Stallions are notorious for seeking out lactating females, and this provides a form of protection against such harassments.
Pregnancy for the Grevy’s zebra typically lasts for 390 days, resulting in the birth of a single foal. The foals are known to follow anything that moves, including other female zebras, and so imprinting of the stripe patterns, vocalizations, and scent are necessary. Often times, mothers will leave their young in “kindergartens” while searching for water, and since the foals do not hide, an adult zebra, typically a dominant male, will assume the role of guardian. A female within this social structure will usually remain under the male’s dominance, and the male will not allow other stallions to mate with her. Although the foal does not belong to male, it will protect the young zebra in order to keep the female in its territory. An adaptation to the semi-arid environment allows the foal to nurse for up to three months before it is able to drink water, and although the foal will lessen its association with the mother at up to six months, it will remain social with her for up to three years.
Grevy’s zebras will feed on grasses, legumes, leaves, fruits, and shoots for nutrition, and they are able to survive on vegetation with lower nutrition value due to their hindgut fermentation digestive systems. They are able to go up to five days without water, although they will drink everyday if water is available. Lactating females require more water than non-lactating females and will often move to areas with more water during the dry seasons. These zebras are prey to animals such as lions, hyenas, cheetahs, leopards, and wild dogs. They are susceptible to intestinal parasites, particularly those of the Trichostrongylus genus. Humans have known of Grevy’s zebra since antiquity where it appeared in roman circuses. Although forgotten in the western world at that time, in the seventeenth century two specimens were sent to Turkey and to the Dutch governor of Jakarta. In 1882, a Grevy’s zebra was given to the French president, establishing the zebra as its own species.
The IUCN has listed Grevy’s zebra as “Endangered”, although as of 2008 their population was considered stable. In the 1970’s there was and estimated population number of 15,000, but by the early 20th century, that number dwindled to 3,500. The current estimation of their population numbers only 2,500 zebras in the wild, with 600 in captivity. It is protected legally in Ethiopia, and in Kenya a hunting ban was placed on Grevy’s zebra in 1977. Hunting was the main threat to these zebras due to the high price of their skins, but now the main threats include competition with livestock and habitat destruction.
There are many areas in Ethiopia where Grevy’s zebra is protected including Yabelo Wildlife Sanctuary, Alledeghi Wildlife Reserve, and Borana Controlled Hunting Area and Chalbi Sanctuary. In Kenya, these areas include Samburu and Shaba National Reserves and Buffalo Springs. Unfortunately, only about .05 percent of wild Grevy’s zebras reside in these protected lands. Community based conservation efforts have proven most effective in keeping the Grevy’s zebra populations stable and preserving their habitats.
Image Caption: The largest species of wild horse in the World. Image taken in Buffalo Springs NP, Kenya. Credit: Rainbirder/Wikipedia(CC BY-SA 2.0)