Theonager (/ˈɒnədʒər/) (Equus hemionus), also known ashemione orAsiatic wild ass, is a species of the familyEquidae native toAsia. A member of the subgenusAsinus, the onager wasdescribed and given its binomial name by German zoologistPeter Simon Pallas in 1775. Six subspecies have been recognized, two of which are extinct.
The onager weighs about 200–260 kg (440–570 lb) and reaches about 2.1 m (6.9 ft) head-body length. They are reddish-brown or yellowish-brown in color and have broad dorsal stripe on the middle of the back. The onager has never been domesticated. It is among thefastest mammals, capable of running 64–70 km/h (40–43 mph).
Other than deserts, it lives ingrasslands,plains,steppes, andsavannahs. Like many other large grazing animals, the onager'srange has contracted greatly under the pressures ofpoaching andhabitat loss. The onager has been classified asNear Threatened on theIUCN Red List in 2015. Of the fivesubspecies, one is extinct, two are endangered, and two are near threatened; its status in China is not well known.
Thespecific name is from theAncient Greekἡμίονος,hēmíonos, fromἡμι-,hēmi-, 'half', andὄνος,ónos, 'donkey'; thus, 'half-donkey' ormule. The termonager comes from the ancient Greekὄναγρος, again fromὄνος,ónos, 'donkey', andἄγριος,ágrios, 'wild'.
The species was commonly known as Asian wild ass, in which case the termonager was reserved for theE. h. onager subspecies,[3] more specifically known as thePersian onager. Until this day, the species share the same name,onager.
The Asiatic wild ass, among Old World equids, existed for more than 4 million years. The oldest divergence ofEquus was the onager followed by the zebras and onwards.[4] A new species called thekiang (E.kiang), aTibetan relative, was previously considered to be a subspecies of the onager asE.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.[5]
One of the largest subspecies of onager. It is 200–250 cm (79–98 in) long, 100–140 cm (39–55 in) tall at the withers, and weighs 200–240 kg (440–530 lb). Male onagers are larger than the females.
Formerly thought to be a distinct species, shown to be a subspecies of Onager by genetic studies in 2017.[6]
Europe, Western Asia
A sixth possible subspecies, the Gobi khulan (E. h. luteus,[2] also called thechigetai[7] ordziggetai) has been proposed, but may be synonymous withE. h. hemionus.
Debates over the taxonomic identity of the onager occurred until 1980. As of 2015[update], four living subspecies and one extinct subspecies of the Asiatic wild ass have been recognized. The Persian onager was formerly known asEquus onager, as it was thought to be a distinct species.
The onager is generally reddish-brown in color during the summer, becoming yellowish-brown or grayish-brown in the winter. It has a black stripe bordered in white that extends down the middle of the back. The belly, the rump, and the muzzle are white, except for the Mongolian wild ass that has a broad black dorsal stripe bordered with white. It is about 200 to 260 kg (440 to 570 lb) in size and 2.1 to 2.5 m (6 ft 11 in to 8 ft 2 in) in head-body length. Male onagers are usually larger than females.
The genusEquus, which includes all extant equines, is believed to have evolved fromDinohippus via the intermediate formPlesippus. One of the oldest species isEquus 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 agedEquus livenzovensis documented from western Europe and Russia.[8]
Molecular phylogenies indicate the most recent common ancestor of all modern equids (members of the genusEquus) 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 4.07Mya for the most recent common ancestor within the range of 4.0 to 4.5Mya.[9] The oldest divergencies are the Asian hemiones (subgenusE. (Asinus), including thekulan, onager, andkiang), followed by the African zebras (subgeneraE. (Dolichohippus), andE. (Hippotigris)). All other modern forms including the domesticated horse (and many fossilPliocene andPleistocene forms) belong to the subgenusE. (Equus) which diverged about 4.8 (3.2–6.5) Mya.[4]
The onagers' favored habitats consist of desert plains, semideserts,oases,arid grasslands, savannahs,shrublands, steppes, mountainous steppes, andmountain 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.[2]
During the latePleistocene era around 40,000 years ago, the Asiatic wild ass ranged widely across Europe and in southwestern to northeastern Asia. It is also known from Middle Pleistocene fossils from the Nefud Desert of Saudi Arabia.[10] The onager has been regionally extinct inIsrael,Saudi Arabia,Iraq,Jordan,Syria, and southern regions ofSiberia.
Onagers at Wadi Lotz, Negev Mountains, Israel
TheMongolian wild ass lives in deserts, mountains, and grasslands of Mongolia andInner Mongolian region of northern China. A few live in northern Xinjiang region of northwestern China, most of which live mainly inKalamaili 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 inEast Asia. TheGobi Desert is the onager's main stronghold. It is regionally extinct in eastern Kazakhstan, southern Siberia, and theManchurian region of China.
TheIndian wild ass 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. ThePersian onager is found in two subpopulations in southern and northern Iran. The larger population is found atKhar Turan National Park. However, it is extirpated from Afghanistan. TheTurkmenian kulan 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.
Like most equids, onagers are social animals.Stallions are either solitary or live in groups of two or three. The males have been observed holdingharems 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. InMongolia andCentral Asia (E. h. hemionus andE. 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 4.5 km2 (1.7 sq mi) to 40 km2 (15 sq mi), where hiking[clarification needed] 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, theplains zebras (E. quagga) andmountain 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 9 km2 (3.5 sq mi), 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[clarification needed] and not in the center. Mares with foals sometimes find themselves in small groups, in areas up to 20 km2 (7.7 sq mi), 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.
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 thegestation 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.
The onager is aherbivore and eats grasses, herbs, leaves, fruits, and saline vegetation when available. In dry habitats, it browses on shrubs and trees, but also feeds on seed pods such asProsopis and breaks up woody vegetation with its hooves to get at more succulent herbs growing at the base of woody plants.The succulent plants of theZygophyllaceae form an important component of its diet in Mongolia during spring and summerWhen natural water sources are unavailable, the onager digs holes in dry riverbeds to reach subsurface water.
An Asiatic lion attacking an onager (Roman,c. AD 150)
The onager is preyed upon by predators such asPersian leopards andstriped hyenas. A few cases of onager deaths due to predation by leopards have been recorded in Iran.[11]
The greatest threat facing the onager is poaching for meat and hides, and in some areas for use in traditional medicine. 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 ofdrought 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 todiseases. 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.
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 ofIsrael since 1982, and had been breeding hybrids there,[12] whilst the Persian onager alone has been reintroduced to Jordan and the deserts of Saudi Arabia.
Quadriga consists of a chariot and a charioteer with four onagers. From Tell Agrab, Iraq. Early Dynastic period, 2600–2370 BCE. Iraq Museum. This is the oldest known model of a quadriga drawn by onagers.
Onagers are notoriously difficult to tame. Equids were used in ancientSumer to pull wagonsc. 2600 BC, and thenchariots on theStandard of Ur,c. 2550 BC. Clutton-Brock (1992) suggests that these weredonkeys rather than onagers on the basis of a "shoulder stripe".[13] However, close examination of the animals (equids,sheep andcattle) 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.[14][15] Genetic testing of skeletons from that era shows that they werekungas, a cross between an onager and a donkey.
^Orlando, L.; Ginolhac, A.; Zhang, G.; Froese, D.; Albrechtsen, A.; Stiller, M.; Schubert, M.; Cappellini, E.; Petersen, B.; et al. (4 July 2013). "RecalibratingEquus evolution using the genome sequence of an early Middle Pleistocene horse".Nature.499 (7456):74–8.Bibcode:2013Natur.499...74O.doi:10.1038/nature12323.PMID23803765.S2CID4318227.
^Stimpson, C. M.; Lister, A.; Parton, Ash; Clark-Balzan, Laine; Breeze, Paul S.; Drake, Nick A.; Groucutt, H. S.; Jennings, R.; Scerri, E. M.L.; White, T. S.; Zahir, M.; Duval, M.; Grün, R.; Al-Omari, A.; Al Murayyi, K. S. M.; Zalmout, I. S.; Mufarreh, Y. A.; Memesh, A. M.; Petraglia, M. D. (2016). "Middle Pleistocene vertebrate fossils from the Nefud Desert, Saudi Arabia: Implications for biogeography and palaeoecology".Quaternary Science Reviews.143:13–36.doi:10.1016/j.quascirev.2016.05.016.hdl:10072/142575.
^Clutton-Brock, Juliet (1992).Horse Power: A History of the Horse and the Donkey in Human Societies. Boston, Massachusetts, US: Harvard University Press.ISBN978-0-674-40646-9.
^Heimpel, Wolfgang (1968).Tierbilder in der Sumerische Literatur. Italy: Studia Pohl 2.
^Maekawa, K. (1979). "The Ass and the Onager in Sumer in the Late Third Millennium B.C.".Acta Sumerologica.I. Hiroshima:35–62.
Duncan, P., ed. (1992).Zebras, Asses, and Horses: An Action Plan for the Conservation of Wild Equids. Gland, Switzerland: IUCN/SSC Equid Specialist Group.ISBN9782831700526.OCLC468402451.
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