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|A Persian onager (Equus hemionus onager) at Rostov-on-Don Zoo, Russia.|
|Equus hemionus range|
The onager or Asiatic wild ass (Equus hemionus) is a large member of the genus Equus of the family Equidae (horse family) native to the deserts and other arid regions of Iran, Pakistan, India and Mongolia, including in cold regions of Kazakhstan, Uzbekistan and Turkmenistan. It formerly had a wider range from southwest to central Asian countries, such as Israel, Saudi Arabia, Iraq, Syria, Afghanistan and Russia.
Like many other large grazing animals, the onager's range has contracted greatly under the pressures of poaching and habitat loss. Of the five subspecies, one is extinct and at least two are endangered (their status in China is not well known).
The specific name is Ancient Greek ἡμίονος (hēmíonos), from ἡμι- (hēmi-), half, and ὄνος (ónos), donkey; thus, half-donkey or mule. In Persian the archaic word gur preserves the second syllable of the common Indo-European term that includes ona/ono (donkey) and ger/gur (swift).
The species was commonly known as Asian wild ass, in which case the term "onager" was reserved for the E. h. onager subspecies, more specifically known as the Persian onager. Until this day, the species share the same name, "onager".
The onagers eats grasses when available, but will browse on shrubs and trees at other times or in drier habitats. It has also been seen feeding on seed pods and breaking up woody vegetation with its hooves to get at more succulent herbs growing at the base of woody plants. During spring and summer in Mongolia, the succulent plants of the Zygophyllaceae family form an important component of the diet of the Mongolian wild ass. This subspecies is also known to eat snow in winter as a substitute for water. At other times when natural water points are unavailable, the Mongolian wild ass will dig holes in dry riverbeds to access sub-surface water. The water holes dug by the wild asses are often subsequently visited by domestic livestock, as well as other wild animals.
Breeding is seasonal, the gestation period in this species is 11 months, and most births occur from April to September. Females with young tend to form groups of up to five females. Males have been observed holding harems of females, but in other studies they defend territories that attract females. It is likely that differences in behaviour and social structure are the result of changes in climate, vegetation cover, predation and hunting. In Mongolia alone, the onager seems to adopt harem type social groups in the southwest and territorial based social groups in the south and southeast.
Onagers are a little larger than donkeys at about 290 kilograms (640 lb) and 2.1 metres (6.9 ft) (head-body length), and are a little more horse-like. 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 in the winter months. They have a black stripe bordered in white that extends down the middle of the back.
Onagers are notoriously untamable. Equids were used in ancient Sumer to pull wagons circa 2600 BC, and then chariots on the Standard of Ur, circa 2550 BC. Clutton-Brock (1992) suggests that these were donkeys 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.
Distribution and range
The onagers' favored habitats are deserts, semi-deserts, arid grasslands, shrublands and mountain steppes. The Turkmenian kulan are known to live in colder regions.
Around 40,000 years ago, in the late Pleistocene era, the Asiatic wild ass ranged widely across Europe to northeastern Asia. They extended as far west as Germany. The current distribution of this species is vastly reduced. The onager have been regionally extinct in Israel, Saudi Arabia, Iraq, Jordan, Syria and southern regions of Siberia.
The Mongolian wild ass is found only in southern Mongolia and parts of northern China, but is by far the most abundant remaining subspecies. The sub-population in southern Mongolia alone accounts for almost 80 percent of the species’ entire population. All other populations number fewer than a hundred individuals. The Indian wild ass was once found throughout the arid part of north-west India (including part of present-day Pakistan), but it is now restricted to a small area of Gujarat. The Persian onager is found in two very small sub-populations in Iran. The Turkmenian kulan is found in Kazakhstan and Turkmenistan, where it has undergone a dramatic decline.
The Turkmenian kulan, Persian onager and Indian wild ass all have very small and highly isolated sub-populations, and so are at great risk of extinction caused by chance events, such as the outbreak of disease or extreme climate events.
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 of the subpopulations is, in itself, a threat, 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 is also a major threat to the onager. It is a particular concern in Mongolia as result of the increasingly dense network of roads, railway lines and fences required to support mining activities.
The Asiatic wild ass is vulnerable to diseases as well. A disease known as the "South African horse sickness" had caused a major decline to the Indian wild ass in the 1960s. Fortunately, the subspecies is no longer under threat to such disease and is continuously increasing their numbers.
The onagers were once under threat by apex predators from India, Iran and Pakistan, as they used to be prey for Asiatic lions, Asian leopards, Asiatic cheetahs, tigers, striped hyenas and dholes. However, until today, the Asiatic wild ass are being strictly protected.
The onager does occur in a number of protected sites where targeted conservation action has been taken. Domestic animals have been removed from some protected areas, and artificial watering holes have been made. Hay is provided for the species and there are hefty fines for poaching. Moreover, 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 Asiatic wild ass; and to conduct further research into the behavior, ecology and taxonomy of the species. Fortunately, several Asiatic wild ass research programs considering these issues are already underway.
There are various breeding programs for the onager subspecies in captivity and in the wild, which increases their numbers to save the endangered 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.
Widely recognized subspecies of the onager include:
- Mongolian wild ass (khulan), Equus hemionus hemionus
- Turkmenian kulan (kulan), Equus hemionus kulan
- Persian onager (gur), Equus hemionus onager
- Indian wild ass (khur), Equus hemionus khur
- Syrian wild ass or hemippe, Equus hemionus hemippus (extinct)
- Moehlman, P. D., Shah, N. & Feh, C. (2008). "Equus hemionus". IUCN Red List of Threatened Species. Version 2010.4. International Union for Conservation of Nature. Retrieved 7 Nov 2010.
- "Asiatic Wild Ass Equus hemionus". IUCN.org. Gland, Switzerland: IUCN/SSC Equid Specialist Group.
- Grubb, P. (2005). "Order Perissodactyla". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 632. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Clutton-Brock, Juliet (1992). Horse Power: A History of the Horse and the Donkey in Human Societies. Boston, Massachusetts, US: Harvard University Press. ISBN 978-0-674-40646-9.
- 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' (Hiroshima) I: 35–62.
- Saltz, D. (1995). "Population dynamics of a reintroduced Asiatic wild ass (Equus Hemionus) herd". Ecological Applications 5(2): 327–335.
- Porter, Valerie (ed.); Ian Lauder Mason (2002). Mason's World Dictionary of Livestock Breeds, Types, and Varieties (5th ed.). Wallingford: CABI. ISBN 0-85199-430-X.
- Duncan, P. (ed.). 1992. Zebras, Asses, and Horses: an Action Plan for the Conservation of Wild Equids. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland.[clarification needed]]]
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