Equus hemionus onager

Geographic Range

Onagers, Equus onager , are found from Mongolia to Saudi Arabia and as far north as southern Russia and Kazakhstan. Some also inhabit northwestern India and Tibet. They have been reintroduced in Mongolia and Iran.

• Biogeographic Regions
• palearctic palearctic
  • introduced introduced
  • native native

Habitat

The flat regions of the deserts and surrounding foothills are home to E. onager . These barren deserts are a harsh environment and receive very little rainfall each year.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune

Physical Description

In comparison with other Asiatic wild asses, E. onager is slightly smaller with a paler coat. Onagers have a pale sandy-red colored coat with a light brown dorsal stripe. The dorsal stripe has two surrounding white strips that blend into the lighter colored hind quarters. In addition to the dorsal stripe, onagers also have a shoulder stripe. The flanks, back and underside of onagers are white. In the winter, the coat grows longer and turns grayer and the white parts become more defined. Males and females differ only slightly outwardly, with males being only slightly larger. Males stand 1.5 meters at the shoulder and are about 2 meters in length, weighing about 250 kilograms.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

A dominant stallion mates with females in the herd. In order to assure breeding status, stallions defend the territories that females move through, with dominant stallions defending the best territories.

• Mating System
• polygynous polygynous

During mating season in mid-June, stallions fight each other for mating rights. Females have a short estrus period of 3 to 5 days. After a year-long gestation, mares leave the herd to give birth in a safe place. A single foal is born that stays with its mother for two years. After giving birth, both mare and foal rejoin the herd, where the mother protects her foal from danger.

Pregnancy in onagers lasts 365 to 368 days. Nowak (1999) reports that lactation in female Equus hemionus (a species of wild ass in which some authorities include onagers) nurse their young for between 1 and 1.5 years. It is reasonable to assume that onagers fall within this range. Young onagers become independent around two years of age. Females are sexually mature around the age of 2, but males, at least in E. hemionus , mature about a year later.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous viviparous

All members of the genus Equus are fairly precocial at birth, and are able to run shortly after birth. During the first two years of a foal's life, it stays with its mother. Mares protect their foals against all dangers. Nursing lasts between 1.5 and 2 years. Although specific details on the relationship between maternal dominance status and status of offsping, it is reasonable to assume that this species is like other members of the genus. If E. onager is like other horses, maternal dominance status affects status of the young within the herd. The role of males in care of offspring has not been reported.

• Parental Investment
• precocial precocial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • protecting
    • female
• maternal position in the dominance hierarchy affects status of young

Lifespan/Longevity

The maximum lifespan of E. onager is reported to be approximately 40 years. However, whether this information is based on wild or captive animals is not known.

Behavior

Equus onager usually lives in herds, with the exception of older stallions, who can be found living alone. Mares live with their foals in herds made up entirely of other females and young.

Data specific to onagers is difficult to find, because of their debated taxonomic status. However, it is reasonable to assume that these animals are similar to E. hemionus , since they are sometimes placed in the same species. With that in mind, the following information on E. hemionus is provided.

Herd size may vary. In E. hemionus , average herds contain between 10 and 20 animals, with one male and many females. However, in some ecological conditions, pressure from predators causes small single male groups to come together.

Onagers are reported to be crepuscular. However, E. hemionus is reported to be primarily diurnal, feeding during the day and bedding down at night, with some populations feeding at night.

Equus hemionus is able to reach top speeds of about 70 km/hour, and can run at a sustained speed of 50 km/hour. It is likely that onagers are similar in their ability to attain such speeds.

• Key Behaviors
• cursorial
• terricolous
• crepuscular crepuscular
• motile motile
• nomadic nomadic
• migratory migratory
• solitary solitary
• social social
• dominance hierarchies dominance hierarchies

Home Range

Because of the harsh conditions that the desert presents, E. onager must stay within 20 kilometers of a water source.

Communication and Perception

Equus onager has strong senses with an extremely keen sense of smell. Like other members of the genus Equus , onagers have vocal, tactile and chemical communication. In addition, visual signals may be important.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Onagers are herbivores that feed on the scarce plant life in the desert. Foods of these animals include grasses, bushes, herbs and foliage. Onagers receive most of their water from their food, but must remain close to a site of open water. Grazing time for onager sis usually during the cooler part of the day such as morning and evening.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems
• seeds, grains, and nuts

Predation

Equus onager has no natural predators other than humans. This species is being driven to extinction due to hunting, competition for food and water with livestock, and loss of natural habitat. Onagers have a well developed sense of smell and can detect potential predators, such as humans, from a far distance. Onagers are also very fast, with the ability to run 60 to 70 kilometers per hour over short distances, and 40 to 50 kilometers per hour for several hours at a time.

Ecosystem Roles

Grazing by E. onager impacts vegetation communities in which they live.

Economic Importance for Humans: Positive

Onagers have been hunted by humans in the past for their flesh and hides. However, in 1971, E. onager became a protected species in Iran and hunting it is prohibited year-round.

• Positive Impacts
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

Although there is no apparent direct negative economic impact that this species has on humans, it is possible that these wild asses compete with livestock for water and scarce food resources.

Conservation Status

IUCN estimates 144 onagers remaining with the rate of decline at 28% over the last three generations.

Other Comments

Onagers are reported to have a bad temperment, which makes them unsuitable as work-a-day domestic animals. However, the ancient Roman Legions are thought to have used these animals to pull their war machines. Onagers were previously considered a species, Equus onager , but have since been included as a subspecies of kulans, Equus hemionus .

Additional Links

Encyclopedia of Life

Contributors

Jill Grogan (author), University of Alaska Fairbanks, Link E. Olson (editor, instructor), University of Alaska Fairbanks, Nancy Shefferly (editor), Animal Diversity Web.

References

AZA Taxon Advisory Group, unknown. "Information for the Upper Level Scientist, Onager (Equus hemionus onager)" (On-line). WILD HORSE RESOURCE. Accessed March 04, 2005 at http://equid.topcities.com/onager.html .

Bennett, D. 1980. Stripes Do Not a Zebra Make, Part I: A Cladistic Analysis of Equus. Systematic Zoology , 29/3: 272-287.

Moehlman, P., C. Feh. 2004. "IUCN Red List of Threatened Species" (On-line). Accessed October 24, 2004 at http://www.redlist.org/search/details.php?species=7966 .

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition . Baltimore and London: The Johns Hopkins University Press.

Wilson, D., D. Reeder. 1993. Mammal Species of the World . Washington, DC: Smithsonian Institution Press.

2003. "IUCN SSC Equid Specialist Group" (On-line). Accessed October 31, 2004 at http://www.iucn.org/themes/ssc/sgs/equid/ASWAss.html .

2004. "Iran Nature and Wildlife Magazine" (On-line). Species Fauna and Flowers. Accessed November 18, 2004 at http://www.hamshahri.org/musiems/daarabad/inwm/no.2/english/fau_flow/ir_mammalia01.html .

2004. "UNEP-WCMC Species Database: CITES-Listed Species" (On-line). Accessed October 31, 2004 at http://www.cites.org/eng/resources/species.html .