Grévy's zebra (''Equus grevyi)'', also known
commonly as the imperial zebra, is the largest living
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of wild
equid
Equidae (commonly known as the horse family) is the Taxonomy (biology), taxonomic Family (biology), family of Wild horse, horses and related animals, including Asinus, asses, zebra, zebras, and many extinct species known only from fossils. The fa ...
and the most threatened of the three species of
zebra
Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: Grévy's zebra (''Equus grevyi''), the plains zebra (''E. quagga''), and the mountain zebra (''E. ...
s, the other two being the
plains zebra
The plains zebra (''Equus quagga'', formerly ''Equus burchellii'') is the most common and geographically widespread species of zebra. Its range is fragmented, but spans much of southern and eastern Africa south of the Sahara. Six or seven subspec ...
and the
mountain zebra. Named after French president
Jules Grévy, it is found in parts of
Kenya
Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...
and
Ethiopia
Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
. 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
The mule is a domestic equine hybrid between a donkey, and a horse. It is the offspring of a male donkey (a jack) and a female horse (a mare). The horse and the donkey are different species, with different numbers of chromosomes; of the two ...
, 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
Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consu ...
, and
browse, such as
acacia
''Acacia'', commonly known as wattles or acacias, is a genus of about of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa, South America, and Austral ...
; 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
A harem is a domestic space that is reserved for the women of the house in a Muslim family. A harem may house a man's wife or wives, their pre-pubescent male children, unmarried daughters, female domestic Domestic worker, servants, and other un ...
, 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
The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...
as
endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...
. 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
Anthrax is an infection caused by the bacterium '' Bacillus anthracis'' or ''Bacillus cereus'' biovar ''anthracis''. Infection typically occurs by contact with the skin, inhalation, or intestinal absorption. Symptom onset occurs between one ...
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
The president of France, officially the president of the French Republic (), is the executive head of state of France, and the commander-in-chief of the French Armed Forces. As the presidency is the supreme magistracy of the country, the po ...
, who, in the 1880s, was given one by the government of
Abyssinia. Traditionally, this species was classified in the subgenus ''Dolichohippus'' with
plains zebra
The plains zebra (''Equus quagga'', formerly ''Equus burchellii'') is the most common and geographically widespread species of zebra. Its range is fragmented, but spans much of southern and eastern Africa south of the Sahara. Six or seven subspec ...
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
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58[Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...](_blank)
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
In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria:
# the grouping contains its own most recent co ...
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
In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...
with plains zebras, the two may gather in same herds and fertile hybrids do occur.
Description
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
The mule is a domestic equine hybrid between a donkey, and a horse. It is the offspring of a male donkey (a jack) and a female horse (a mare). The horse and the donkey are different species, with different numbers of chromosomes; of the two ...
-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.
Range and ecology
Grévy's zebra largely inhabits northern Kenya
Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...
, with some isolated populations in Ethiopia
Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
. It was extirpated
Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions.
Local extinctions mark a chan ...
from Somalia
Somalia, officially the Federal Republic of Somalia, is the easternmost country in continental Africa. The country is located in the Horn of Africa and is bordered by Ethiopia to the west, Djibouti to the northwest, Kenya to the southwest, th ...
and Djibouti
Djibouti, officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red Sea and the Gulf of Aden to the east. The country has an area ...
and its status in South Sudan
South Sudan (), officially the Republic of South Sudan, is a landlocked country in East Africa. It is bordered on the north by Sudan; on the east by Ethiopia; on the south by the Democratic Republic of the Congo, Uganda and Kenya; and on the ...
is uncertain.[ Database entry includes a brief justification of why this species is endangered.] It lives in ''Acacia
''Acacia'', commonly known as wattles or acacias, is a genus of about of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa, South America, and Austral ...
''-''Commiphora
''Commiphora'' is the most species-rich genus of flowering plants in the frankincense and myrrh family, Burseraceae. The genus contains approximately 190 species of shrubs and trees, which are distributed throughout the (sub-) tropical regions of A ...
'' bushlands and barren plains. Ecologically, this species is intermediate between the arid-living African wild ass and the water-dependent plains zebra. Lactating
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The proces ...
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 grass
Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...
es, legume
Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consum ...
s, and browse for nutrition. They commonly browse when grasses are not plentiful. Their hindgut fermentation
Hindgut fermentation is a digestive process seen in monogastric herbivores (animals with a simple, single-chambered stomach). Cellulose is digested with the aid of symbiotic microbes including bacteria, archaea, and eukaryotes. The microbial fe ...
digestive system allows them to subsist on diets of lower nutritional quality than that necessary for ruminant
Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microb ...
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
Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The proces ...
. During droughts, the zebras will dig water holes and defend them. The Grévy's zebra's main predator is the lion
The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'', native to Sub-Saharan Africa and India. It has a muscular, broad-chested body (biology), body; a short, rounded head; round ears; and a dark, hairy tuft at the ...
, but adults can be hunted by spotted hyena
The spotted hyena (''Crocuta crocuta''), also known as the laughing hyena, is a hyena species, currently classed as the sole extant member of the genus ''Crocuta'', native to sub-Saharan Africa. It is listed as being of least concern by the IUC ...
s. African hunting dogs, cheetah
The cheetah (''Acinonyx jubatus'') is a large Felidae, cat and the Fastest animals, fastest land animal. It has a tawny to creamy white or pale buff fur that is marked with evenly spaced, solid black spots. The head is small and rounded, wit ...
s and leopard
The leopard (''Panthera pardus'') is one of the five extant cat species in the genus ''Panthera''. It has a pale yellowish to dark golden fur with dark spots grouped in rosettes. Its body is slender and muscular reaching a length of with a ...
s almost never attack adults, even in desperate times, but sometimes prey on young animals, although mares are fiercely protective of their young. In addition, they are susceptible to various gastro-intestinal parasites, notably of the genus '' Trichostrongylus''.
Behaviour and life history
Adult stallions mostly live in territories during the wet seasons but some may stay in them year round if there's enough water left. Stallions that are unable to establish territories are free-ranging and are known as bachelors. Mares, young and non-territorial stallions wander through large home ranges. The mares will wander from territory to territory preferring the ones with the highest-quality food and water sources. Up to nine stallions may compete for a mare outside of a territory. Territorial stallions will tolerate other stallions who wander in their territory. However, when an oestrous mare is present the territorial stallion keeps other stallions at bay. Non-territorial stallions might avoid territorial ones because of harassment. When mares are not around, a territorial stallion will seek the company of other stallions. The stallion shows his dominance with an arched neck and a high-stepping gait and the least dominant stallions submit by extending their tail, lowering their heads and nuzzling their superior's chest or groin.
Zebras produce numerous sounds and vocalisations. When alarmed, they produce deep, hoarse grunts. Whistles and squeals are also made when alarmed, during fights, when scared or in pain. Snorts may be produced when scared or as a warning. A stallion will bray in defense of his territory, when driving mares, or keeping other stallions at bay. Barks may be made during copulation and distressed foals will squeal. The call of the Grévy's zebra has been described as "something like a hippo
The hippopotamus (''Hippopotamus amphibius;'' ; : hippopotamuses), often shortened to hippo (: hippos), further qualified as the common hippopotamus, Nile hippopotamus and river hippopotamus, is a large semiaquatic Mammal, mammal native to su ...
's grunt combined with a donkey
The donkey or ass is a domesticated equine. It derives from the African wild ass, ''Equus africanus'', and may be classified either as a subspecies thereof, ''Equus africanus asinus'', or as a separate species, ''Equus asinus''. It was domes ...
's wheeze". To get rid of flies or parasites, they roll in dust, water or mud or, in the case of flies, they twitch their skin. They also rub against trees, rocks and other objects to get rid of irritations such as itchy skin, hair or parasites. Although Grévy's zebras do not perform mutual grooming, they do sometimes rub against a conspecific.
Reproduction
Grévy's zebras can mate and give birth year round, but most mating takes place in the early rainy seasons and births mostly take place in August or September after the long rains. An oestrous mare may visit as many as four territories a day and will mate with the stallions in them. Among territorial stallions, the most dominant ones control territories near water sources, which mostly attract mares with dependant foals, while more subordinate stallions control territories away from water with greater amounts of vegetation, which mostly attract mares without dependant foals.[Rubenstein, D. I. (2010]
"Ecology, social behavior, and conservation in zebras"
pp. 231–58. In: ''Advances in the Study Behavior: Behavioral Ecology of Tropical Animals'', Vol. 42. R. Macedo, ed. Elsevier Press.
The resident stallions of territories will try to subdue the entering mares with dominance rituals and then continue with courtship and copulation. Grévy's zebra stallions have large testicles and can ejaculate a large amount of semen
Semen, also known as seminal fluid, is a bodily fluid that contains spermatozoon, spermatozoa which is secreted by the male gonads (sexual glands) and other sexual organs of male or hermaphrodite, hermaphroditic animals. In humans and placen ...
to replace the sperm of other males. 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. While mare associations with individual stallions are brief and mating is promiscuous
Promiscuity is the practice of engaging in sexual activity frequently with different partners or being indiscriminate in the choice of sexual partners. The term can carry a moral judgment. A common example of behavior viewed as promiscuous by man ...
, mares who have just given birth will reside within a territory protected by a territorial stallion. Lactating mares have higher water requirements than non-lactating mares, and stallions typically control areas near water. Lactating females are harassed by stallions more often than non-lactating ones and thus associating with one male and his territory provides an advantage as he will guard against other males.
Gestation of the Grévy's zebra normally lasts 390 days, with a single foal being born. A newborn zebra will follow anything that moves, so new mothers prevent other mares from approaching their foals while imprinting their own striping pattern, scent and vocalisation on them. Mares with young foals may gather into small groups. Mares may leave their foals in "kindergartens" in a stallion's territory while searching for water when grazing conditions are poor. The foals will not hide, so they can be vulnerable to predators. While the foal may not be his, the stallion will tolerate it to ensure that the mare stays in his territory. 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.
Relationship with humans
The Grévy's zebra was known to the Europeans in antiquity and was used by the Romans in circuses
A circus is a company of performers who put on diverse entertainment shows that may include clowns, acrobats, trained animals, trapeze acts, musicians, dancers, hoopers, tightrope walkers, jugglers, magicians, ventriloquists, and unicyc ...
. It was subsequently forgotten in the Western world for a thousand years. In the seventeenth century, the king of Shoa (now central Ethiopia) exported two zebras; one to the Sultan of Turkey and another to the Dutch governor of Jakarta
Jakarta (; , Betawi language, Betawi: ''Jakartè''), officially the Special Capital Region of Jakarta (; ''DKI Jakarta'') and formerly known as Batavia, Dutch East Indies, Batavia until 1949, is the capital and largest city of Indonesia and ...
. A century later, in 1882, the government of Abyssinia sent one to French president Jules Grévy. It was at that time that the animal was recognised as its own species and named in Grévy's honour. Grévy's zebra appears on the Eritrean 25-cent coin.
Status and conservation
The Grévy's zebra is considered endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...
.[ Its population was estimated to be 15,000 in the 1970s and by the early 21st century the population was lower than 3,500, a 75% decline.] 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.[
There are also an estimated 600 Grévy's zebras in captivity.] Captive herds have been known to thrive, like at White Oak Conservation in Yulee, Florida, United States, where more than 70 foals have been born. There, research is underway in partnership with the Conservation Centers for Species Survival on semen collection and freezing and on artificial insemination.
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. Community-based conservation efforts have shown to be the most effective in preserving Grévy's zebras and their habitat. Less than 0.5% of the range of the Grévy's zebra is in protected areas. In Ethiopia, the protected areas include Aledeghi Wildlife Reserve, Yabelo Wildlife Sanctuary, Borana National Park, and Chelbi Sanctuary. In Kenya, important protected areas include the Buffalo Springs, Samburu and Shaba National Reserves and the private and community land wildlife conservancies in Isiolo, Samburu and the Laikipia Plateau.[
The mesquite plant was introduced into Ethiopia around 1997 and is endangering the zebra's food supply. An invasive species, it is replacing the two grass species, '' Cenchrus ciliaris'' and '' Chrysopogon plumulosus,'' which the zebras eat for most of their food.]
References
External links
"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
– Rich Blundell reports from Kenya
Grevy's Zebra Trust
– a Kenyan organization dedicated to preserving the Grévy's zebra
{{Good article
EDGE species
Grévy's zebra
Mammals of Kenya
Mammals of Ethiopia
Mammals of South Sudan
Fauna of East Africa
Fauna of the Horn of Africa
Grévy's zebra