|A Persian onager (Equus hemionus onager) at Rostov-on-Don Zoo, Russia.|
|Equus hemionus range|
The onager, also known as hemione or Asiatic wild ass (Equus hemionus) is a large Equid of the family Equidae (horse family) native to Asia. Unlike most horses, donkeys and even zebras, the onagers have never been domesticated. The onagers are among the fastest mammals, as they can run as fast as 64 km/h (40 mph) to 70 km/h (43 mph).
The onager is closely related to the African wild ass, as they both shared the same ancestor. The kiang, formerly considered a subspecies of the genus Equus hemionus, diverged from the Asiatic wild ass and has been acknowledged as a distinct species.
The onager formerly had a wider range from southwest, central to northern Asian countries, such as Israel, Saudi Arabia, Iraq, Syria, Afghanistan, Russia and Siberia. During early 20th century, the species lost most of its ranges in the Middle East and Eastern Asia. Today the onagers live in deserts and other arid regions of Iran, Pakistan, India and Mongolia, including in Central Asian hot and cold deserts of Kazakhstan, Uzbekistan, Turkmenistan and China. Other than deserts, it lives in grasslands, plains, steppes and savannahs.
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, one is critically endangered and three are endangered (their status in China is not well known). The Persian onagers are currently being reintroduced in the Middle East as replacement for the extinct Syrian wild ass.
Etymology and taxonomy
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".
Widely recognized subspecies of the onager include:
- Mongolian wild ass (khulan), Equus hemionus hemionus - (China, Kazakhstan, Mongolia and Siberia)
- Turkmenian kulan (kulan), Equus hemionus kulan - (Afghanistan, China, Kazakhstan, Kyrgyzstan, Siberia, Tajikistan, Turkmenistan and Uzbekistan)
- Persian onager (gur), Equus hemionus onager - (Afghanistan, Iran, Iraq and Pakistan)
- Indian wild ass (khur), Equus hemionus khur - (India and Pakistan)
- †Syrian wild ass (hemippe), Equus hemionus hemippus - Extinct (Iraq, Israel, Jordan, Saudi Arabia, Syria and Turkey)
There were debates over the taxonomic identity of the onager until in 1980. As of today, 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.
The Asiatic wild ass, among Old World equids existed for more than 4 million years ago. The oldest divergence of Equus was the onager followed by the zebras and onwards. 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 that it is a distinct species, having diverged from the closest relative of the Mongolian wild ass's ancestor in less than 500,000 years ago.
Onagers are 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. Male onagers are usually larger than females.
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 hot and colder deserts.
During the late Pleistocene era around 40,000 years ago, the Asiatic wild ass ranged widely across Europe to northeastern Asia. The onager have been regionally extinct in Israel, Saudi Arabia, Iraq, Jordan, Syria and southern regions of Siberia.
The Mongolian wild ass lives in deserts of Mongolia and northern China and is the most common subspecies, however their populations have decreased to a few thousands due to years of poaching and habitat loss. It is regionally extinct in eastern Kazakhstan and Siberia. The Indian wild ass was once found throughout the arid parts and desert steppes of northwest India and Pakistan, but approximately 4,500 of them are found in a few very hot wildlife sanctuaries of Gujarat. The Persian onager is found in two sub-populations in southern and northern Iran. The larger population is found at Khar Turan National Park. However, it is extinct in the wild of Afghanistan. The Turkmenian kulan used to be widespread in central to north Asia. However, it is now found only in Turkmenistan and has been reintroduced in southern Kazakhstan.
Like all equids, the onagers are herbivorous mammals. They eat grasses, herbs, leaves, fruits and saline vegetation when available, but will browse on shrubs and trees in drier habitats. It has also been seen feeding on seed pods such as Prosopis and breaking up woody vegetation with its hooves to get at more succulent herbs growing at the base of woody plants.
During the winter, the onagers would also eat snow as a substitute for water. When natural water points are unavailable, the Asiatic wild ass will dig up 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. Water is also found in the plants the onagers feed on.
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.
Biology and behavior
Asiatic wild ass are mostly active at dawn and dusk even during the intense heat.
Breeding is seasonal, the gestation period of the onagers is 11 months, and most births occur from April to September. The mating season of the onagers, such as those in India is in the rainy season. Females with the young tend to form groups of up to five females.
Like most equids, onagers are social animals. Stallions are either solitary or they 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. 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 can adopt harem type social groups in the southwest and territorial based social groups in the south and southeast.
The onager is preyed upon by leopards, gray wolves and hyenas (formerly by tigers and lions), however, they are known to have anti-predator protection. Group of stallions will cooperate and try to chase off predators. If threatened, the onagers will defend themselves and violently kick at the incoming predator.
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.
The greatest threat facing the onager is poaching for meat and hides, and in some areas for use in traditional medicine. It is the one of 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 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, Asiatic cheetahs, tigers, striped hyenas and dholes. However, until today, the Asiatic wild ass are being strictly protected. However, Asiatic leopards and grey wolves are the current threats of the onagers. A few cases of onager deaths due to predation was recorded in Iran, as a Persian leopard attacked and eaten a Persian onager. It is said that leopards do not usually feed on equids such as in Africa. It may be due that Asian leopards are larger and stronger enough to prey on Asiatic wild ass.
There are various breeding programs 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. Fortunately, several Asiatic wild ass research programs considering these issues are already underway.
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.
- 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.
- Ryder, O.A. & Chemnick, L.G. (1990). "Chromosomal and molecular evolution in Asiatic wild asses". Genetica 83 (1): 67–72. doi:10.1007/BF00774690.
- Grubb, P. (2005). "Order Perissodactyla". In Wilson, D.E.; Reeder, D.M. Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 632. ISBN 978-0-8018-8221-0. OCLC 62265494.
- 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.
- Weinstock, J.; et al. (2005). "Evolution, systematics, and phylogeography of Pleistocene horses in the New World: a molecular perspective". PLoS Biology 3 (8): e241. doi:10.1371/journal.pbio.0030241. PMC 1159165. PMID 15974804. Retrieved 2008-12-19.
- Ryder OA, Chemnick LG. (1990). "Chromosomal and molecular evolution in Asiatic wild asses.". PubLMed.gov. Retrieved 14 October 2015.
- 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. doi:10.2307/1942025.
- 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]]]
|Wikimedia Commons has media related to Equus hemionus.|