Onager Asiatischer Wildesel Equus hemionus onager Zoo Augsburg-04.jpg
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The onager (; ''Equus hemionus'' ), A new species called the kiang (''E. kiang''), a Tibetan relative, was previously considered to be a subspecies of the onager as ''E. hemionus kiang'', but recent molecular studies indicate it to be a distinct species, having diverged from the closest relative of the Mongolian wild ass's ancestor less than 500,000 years ago.


Subspecies

Five widely recognized subspecies of the onager include: A sixth possible subspecies, the Gobi khulan (''E. h. luteus'', also called the ''chigetai'' or ''dziggetai'') has been proposed, but may be synonymous with ''E. h. hemionus''. Debates over the taxonomic identity of the onager occurred until 1980. , four living subspecies and one extinct subspecies of the Asiatic wild ass have been recognized. The Persian onager was formerly known as ''Equus onager'', as it was thought to be a distinct species.


Characteristics

Onagers are the most horse-like of wild asses. They are short-legged compared to horses, and their coloring varies depending on the season. They are generally reddish-brown in color during the summer, becoming yellowish-brown or grayish-brown in the winter. They have a black stripe bordered in white that extends down the middle of the back. The belly, the rump, and the muzzle are white in most onagers, except for the Mongolian wild ass that has a broad black dorsal stripe bordered with white. Onagers are larger than donkeys at about in size and in head-body length. Male onagers are usually larger than females.


Evolution

The genus ''Equus'', which includes all extant equines, is believed to have evolved from ''
Dinohippus ''Dinohippus'' (Greek: "Terrible horse") is an extinct equid which was endemic to North America from the late Hemphillian stage of the Miocene through the Zanclean stage of the Pliocene (10.3—3.6 mya) and in existence for approximately . Fossi ...
'' via the intermediate form ''
Plesippus ''Plesippus'' is a genus of extinct horse from the Pleistocene of North America. Although commonly seen as a subgenus of ''Equus'' recent cladistic analysis considers it a distinct genus. Species Two species are recognized by Barron et al. (201 ...
''. One of the oldest species is '' Equus simplicidens'', described as zebra-like with a donkey-shaped head. The oldest fossil to date is about 3.5 million years old from Idaho, USA. The genus appears to have spread quickly into the Old World, with the similarly aged ''Equus livenzovensis'' documented from western Europe and Russia. Molecular phylogenies indicate the most recent common ancestor of all modern equids (members of the genus ''Equus'') lived around 5.6 (3.9–7.8) million years ago (Mya). Direct paleogenomic sequencing of a 700,000-year-old middle Pleistocene horse metapodial bone from Canada implies a more recent 4.07 Mya for the most recent common ancestor within the range of 4.0 to 4.5 Mya. The oldest divergencies are the Asian hemiones (subgenus ''E. ( Asinus)'', including the kulan, onager, and kiang), followed by the African zebras (subgenera ''E. ( Dolichohippus)'', and ''E. (
Hippotigris Zebras (, ) (subgenus ''Hippotigris'') are African equines with distinctive black-and-white striped coats. There are three living species: the Grévy's zebra (''Equus grevyi''), plains zebra (''E. quagga''), and the mountain zebra (''E. zebra ...
)''). All other modern forms including the domesticated horse (and many fossil Pliocene and Pleistocene forms) belong to the subgenus ''E. (
Equus Equus may refer to: * ''Equus'' (genus), a genus of animals including horses, donkeys and zebras * ''Equus'' (play), a play by Peter Shaffer * ''Equus'' (film), a film adaptation of the Peter Shaffer play * Equus (comics), a comic book characte ...
)'' which diverged about 4.8 (3.2–6.5) Mya.


Distribution and habitat

The onagers' favored habitats consist of desert plains, semideserts,
oases In ecology, an oasis (; ) is a fertile area of a desert or semi-desert environment'ksar''with its surrounding feeding source, the palm grove, within a relational and circulatory nomadic system.” The location of oases has been of critical imp ...
, arid grasslands, savannahs,
shrubland Shrubland, scrubland, scrub, brush, or bush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity. It m ...
s, steppes, mountainous steppes, and mountain ranges. The Turkmenian kulan and Mongolian wild asses are known to live in hot and colder deserts. The IUCN estimates about 28,000 mature individuals in total remain in the wild. During the late Pleistocene era around 40,000 years ago, the Asiatic wild ass ranged widely across Europe and in southwestern to northeastern Asia. The onager has been regionally extinct in Palestine, Saudi Arabia, Iraq, Jordan,
Syria Syria ( ar, سُورِيَا or سُورِيَة, translit=Sūriyā), officially the Syrian Arab Republic ( ar, الجمهورية العربية السورية, al-Jumhūrīyah al-ʻArabīyah as-Sūrīyah), is a Western Asian country loc ...
, and southern regions of Siberia. The Mongolian wild ass lives in deserts, mountains, and grasslands of Mongolia and Inner Mongolian region of northern China. A few live in northern Xinjiang region of northwestern China, most of which live mainly in Kalamaili Nature Reserve. It is the most common subspecies, but its populations have drastically decreased to a few thousand due to years of poaching and habitat loss in East Asia. The
Gobi Desert The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world. Geography The Gobi measures from southwest to northeast an ...
is the onager's main stronghold. It is regionally extinct in eastern Kazakhstan, southern Siberia, and the Manchurian region of China. The
Indian wild ass The Indian wild ass (''Equus hemionus khur''), also called the Indian onager or, in the local Gujarati language, Ghudkhur and Khur, is a subspecies of the onager native to South Asia. It is currently listed as Near Threatened by IUCN. The prev ...
was once found throughout the arid parts and desert steppes of northwest India and Pakistan, but about 4,500 of them are found in a few very hot wildlife sanctuaries of Gujarat. The Persian onager is found in two subpopulations in southern and northern Iran. The larger population is found at
Khar Turan National Park Khar Turan National Park or Touran Wildlife Refuge is a National Park in Iran. It is situated in the Semnan province, southeast of Shahrud. With a size of , it is the second largest reserve in Iran. Khar Turan National Park also called the litt ...
. However, it is extirpated from Afghanistan. The
Turkmenian kulan The Turkmenian kulan (''Equus hemionus kulan''), also called Transcaspian wild ass, Turkmenistani onager or simply the ', is a subspecies of onager (Asiatic wild ass) native to Central Asia. It was declared Endangered in 2016. The species's popu ...
used to be widespread in central to north Asia. However, it is now found in Turkmenistan and has been reintroduced in southern Kazakhstan and Uzbekistan.


Biology and behavior

Asiatic wild asses are mostly active at dawn and dusk, even during the intense heat.


Social structure

Like most equids, onagers are social animals.
Stallion A stallion is a male horse that has not been gelded (castrated). Stallions follow the conformation and phenotype of their breed, but within that standard, the presence of hormones such as testosterone may give stallions a thicker, "cresty" nec ...
s are either solitary or live in groups of two or three. The males have been observed holding harems of females, but in other studies, the dominant stallions defend territories that attract females. Differences in behaviour and social structure likely are the result of changes in climate, vegetation cover, predation, and hunting. The social behavior of the Asian wild ass can vary widely, depending on different habitats and ranges, and on threats by predators including humans. In Mongolia and Central Asia (''E. h. hemionus'' and ''E. h. kulan''), an onager stallion can adopt harem-type social groups, with several mares and foals in large home areas in the southwest, or in territory-based social groups in the south and southeast. Also, annual large hikes occur, covering to , where hiking in summer is more limited than in the winter. Onagers also occasionally form large group associations of 450 to 1,200 individuals, but this usually only occurs in places with food or water sources. As these larger groups dissolve again within a day, no overarching hierarchy apart from the ranking of the individual herds seems to exist. Young male onagers also frequently form "bachelor groups" during the winter. Such a lifestyle is also seen in the wild horse, the plains zebras (''E. quagga'') and mountain zebras (''E. zebra''). Southern populations of onagers in the Middle East and South Asia tend to have a purely territorial life, where areas partly overlap. Dominant stallions have home ranges of , but they can also be significantly larger. These territories include food and rest stops and permanent or periodic water sources. The waters are usually at the edge of a coalfield and not in the center. Mares with foals sometimes find themselves in small groups, in areas up to , which overlap with those of the other groups and dominant stallions. Such features are also seen among Grévy's zebras (''E. grevyi'') and the African wild asses.


Reproduction

The Asian wild ass is sexually mature at two years old, and the first mating usually takes place at three to four years old. Breeding is seasonal, and the
gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
period of onagers is 11 months; the birth lasts a little more than 10 minutes. Mating and births occur from April to September, with an accumulation from June to July. The mating season in India is in the rainy season. The foal can stand and starts to nurse within 15 to 20 minutes. Females with young tend to form groups of up to five females. During rearing, a foal and dam remain close, but other animals and her own older offspring are displaced by the dam. Occasionally, stallions in territorial wild populations expel the young to mate with the mare again. Wild Asian wild asses reach an age of 14 years, but in captivity, they can live up to 26 years.


Diet

Like all equids, onagers are herbivorous mammals. They eat grasses, herbs, leaves, fruits, and saline vegetation when available, but browse on shrubs and trees in drier habitats. They have also been seen feeding on seed pods such as '' Prosopis'' and breaking up woody vegetation with their hooves to get at more succulent herbs growing at the base of woody plants. During the winter, onagers also eat snow as a substitute for water. When natural water sources are unavailable, the onager digs holes in dry riverbeds to reach subsurface water. The water holes dug by the onagers are often subsequently visited by domestic livestock, as well as other wild animals. Water is also found in the plants on which the onagers feed. During spring and summer in Mongolia, the succulent plants of the Zygophyllaceae form an important component of the diet of the Mongolian wild ass.


Predation

The onager is preyed upon by predators such as
Persian leopard ''Panthera pardus tulliana'' is a leopard subspecies native to the Iranian Plateau and surrounding areas encompassing Turkey, the Caucasus, Azerbaijan, Georgia, Armenia, Iraq, Iran, Turkmenistan, Afghanistan and possibly Pakistan. Since 2016, i ...
s and striped hyenas. A few cases of onager deaths due to predation by leopards were recorded in Iran. Though leopards do not usually feed on equids as in Africa, this may be because Persian leopards are larger and strong enough to prey on Asiatic wild asses. In the Middle East and the Indian subcontinent, Asiatic lions and tigers were the main predators of onagers. They were also formerly preyed upon by dholes,
Asiatic cheetah The Asiatic cheetah (''Acinonyx jubatus venaticus'') is a critically endangered cheetah subspecies currently only surviving in Iran. It once occurred from the Arabian Peninsula and the Near East to the Caspian region, Transcaucasus, Kyzylkum D ...
s, and possibly
bear Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Nor ...
s, though they may have mostly preyed only on onager
foal A foal is an equine up to one year old; this term is used mainly for horses, but can be used for donkeys. More specific terms are colt for a male foal and filly for a female foal, and are used until the horse is three or four. When the foal i ...
s. In India, mugger crocodiles can be great threats to onagers during migratory river crossings. Currently, the main predator for onagers are gray wolves. However, like most equids, they are known to have antipredator behaviour. Groups of stallions cooperate and try to chase off predators. If threatened, onagers defend themselves and violently kick at the incoming predator.


Threats

The greatest threat facing the onager is poaching for meat and hides, and in some areas for use in traditional medicine. It is one of the highest threats for the Mongolian wild ass. The extreme isolation of many subpopulations also threatens the species, as genetic problems can result from inbreeding. Overgrazing by livestock reduces food availability, and herders also reduce the availability of water at springs. The cutting down of nutritious shrubs and bushes exacerbates the problem. Furthermore, a series of drought years could have devastating effects on this beleaguered species. Habitat loss and fragmentation are also major threats to the onager, a particular concern in Mongolia as a result of the increasingly dense network of roads, railway lines, and fences required to support mining activities. The Asiatic wild ass is also vulnerable to
diseases A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that ar ...
. A disease known as the "South African horse sickness" caused a major decline to the Indian wild ass population in the 1960s. However, the subspecies is no longer under threat to such disease and is continuously increasing in number.


Conservation

Various breeding programs have been started for the onager subspecies in captivity and in the wild, which increases their numbers to save the endangered species. The species is legally protected in many of the countries in which it occurs. The priority for future conservation measures is to ensure the protection of this species in particularly vulnerable parts of its range, to encourage the involvement of local people in the conservation of the onager, and to conduct further research into the behavior, ecology, and taxonomy of the species. Two onager subspecies, the Persian onager and the Turkmenian kulan are being reintroduced to their former ranges, including in other regions the Syrian wild ass used to occur in the Middle East. The two subspecies have been reintroduced to the wild of Israel since 1982, and had been breeding hybrids there, whilst the Persian onager alone has been reintroduced to Jordan and the deserts of Saudi Arabia.


Relationship with humans

Onagers are notoriously difficult to tame. Equids were used in ancient
Sumer Sumer () is the earliest known civilization in the historical region of southern Mesopotamia (south-central Iraq), emerging during the Chalcolithic and early Bronze Ages between the sixth and fifth millennium BC. It is one of the cradles of c ...
to pull wagons , and then
chariot A chariot is a type of cart driven by a charioteer, usually using horses to provide rapid motive power. The oldest known chariots have been found in burials of the Sintashta culture in modern-day Chelyabinsk Oblast, Russia, dated to c. 2000&nbs ...
s on the
Standard of Ur The Standard of Ur is a Sumerian artifact of the 3rd millennium BC that is now in the collection of the British Museum. It comprises a hollow wooden box measuring wide by long, inlaid with a mosaic of shell, red limestone and lapis lazuli. It ...
, . Clutton-Brock (1992) suggests that these were
donkey The domestic donkey is a hoofed mammal in the family Equidae, the same family as the horse. It derives from the African wild ass, ''Equus africanus'', and may be classified either as a subspecies thereof, ''Equus africanus asinus'', or as a ...
s rather than onagers on the basis of a "shoulder stripe". However, close examination of the animals (equids, sheep and cattle) on both sides of the piece indicate that what appears to be a stripe may well be a harness, a trapping, or a joint in the inlay. Genetic testing of skeletons from that era shows that they were kungas, a cross between an onager and a donkey.


In literature

In the Hebrew Bible there is a reference to the onager in Job 39:5: In by Honoré de Balzac, the onager is identified as the animal from which comes the ass' skin or
shagreen Shagreen is a type of rawhide consisting of rough untanned skin, historically from a horse's or onager's back, or from shark or ray. Etymology The word derives from the French ''chagrin'' and is related to Italian ''zigrino'' and Venetian '' ...
of the title. A short poem by Ogden Nash also features the onager:


References

*


External links


"Ass"
'' Encyclopædia Britannica''
''Equus hemionus'' bibliography
at The Biodiversity Heritage Library {{Authority control EDGE species Asinus Extant Pliocene first appearances Fauna of the Middle East Fauna of Iran Fauna of Iraq Fauna of Western Asia Mammals described in 1775 Mammals of Afghanistan Mammals of Central Asia Mammals of Mongolia Mammals of Pakistan Near threatened biota of Asia