Wild horse

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This article is about genetically wild horses which have never been domesticated. For the free-roaming feral horses of the Americas, see Mustang (horse). For Domesticated horses which have reverted to the wild, see Feral horse.
Wild horse
Przewalski's Horse
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Genus: Equus
Subgenus: Equus
Species: E. ferus
Binomial name
Equus ferus
Boddaert, 1785
Subspecies
'Bred back' Tarpan in Haselünne, Germany (2004)
'Bred back' Tarpan in Haselünne, Germany (2004)

The Wild Horse (Equus ferus) is a member of the Horse genus which currently is native only in Asia. The true wild horse is not merely a feral horse like the Mustang; a true wild horse species is one which was never successfully domesticated.

Two species or subspecies (taxonomy is debated) of wild horses survived into modern times: The Tarpan or Eurasian Wild Horse (Equus ferus ferus), once native to Europe and Asia, and Przewalski's Horse, also known as the Mongolian Wild Horse or Takhi (classification disputed, either Equus ferus przewalskii or Equus przewalskii), native to Central Asia and the Gobi Desert. The Tarpan became extinct in captivity in Ukraine in 1918 or 1919. The Przewalski's Horse is still found today, though it is an endangered species and for a time was considered extinct in the wild. Roughly 1500 animals are protected in zoos around the world, and today, a small breeding population has been reintroduced in Mongolia.[1] As of 2005, a cooperative venture between the Zoological Society of London and Mongolian Scientists has resulted in a free-ranging population of 248 animals in the wild.[2]

Przewalski's Horse has notable biological differences from the domestic horse; unlike domesticated horses, which have 64 chromosomes, the wild horse has 66 chromosomes. However, the offspring of Przewalski and domestic horses are fertile, possessing 65 chromosomes.[3]

Other species of wild horses were once indigenous to North America, as well, populating the continent before and during the last Ice Age. Approximately 10,000 years ago, some horses in the Western Hemisphere migrated to Eurasia across the Bering land bridge, and fanned out from Siberia to the rest of Asia, Europe, and the Middle East. What horses remained behind became extinct in North America. There are several competing theories about why this happened. One theory holds that climate changes associated with the end of the last Ice Age caused the extinction of the horse, the mammoth and other large land animals. Another theory holds that newly-arrived humans hunted horses to extinction. A third holds that the newly arrived humans brought a biological factor which caused the demise of horses and other large ungulates in the Americas. It is also possible that it was a combination of factors.[4]

Contents

[edit] History

Only two never-domesticated "wild" groups survived into historic times, Przewalski's horse, or Equus ferus przewalski, and the Tarpan, or Equus ferus ferus[5] Przewalski's horse occupied the eastern Eurasian steppes, perhaps from the Urals to Mongolia, although the ancient border between Tarpan and Przewalksi distributions has not been clearly defined. The Tarpan became extinct in the late 19th century. Przewalski's horse was limited to Dzungaria and western Mongolia in the same period, became extinct in the wild during the 1960s, but was re-introduced in the late 1980s to two preserves in Mongolia. Although researchers such as Marija Gimbutas theorized that the horses of the Chalcolithic period were Przewalski's, more recent genetic studies indicate that Przewalski's horse is not an ancestor to modern domesticated horses. However, other subspecies of Equus ferus, may have existed and could have been the stock from which domesticated horses are descended.[5]

[edit] Taxonomy

While taxonomy is debated, one view is that the wild horse and domestic horse belong to the same species. Thus, to conform to the Code of the International Commission of Zoological Nomenclature the scientific name of the wild horse Equus ferus was discontinued by Wilson and Reeder in 1993 and wild horses were added to Equus caballus, the name given by Linnaeus. Some scientists criticized this change of the scientific name, arguing in favor of a distinction between wild and feral or domesticated animals.[6]

As a result, in 2003, the International Commission on Zoological Nomenclature "conserved the usage of 17 specific names based on wild species, which are pre-dated by or contemporary with those based on domestic forms", re-confirming Equus ferus for the wild horse. Taxonomists who consider the domestic horse a subspecies of the wild horse should use Equus ferus caballus but the name Equus caballus remains available for the domestic horse where it is considered to be a separate species.[7]

[edit] Feral horses

Feral horse in the Pentland Hills, Scotland. Feral horses, though popularly called "wild" horses, are not truly wild; their ancestors were domesticated animals.
Feral horse in the Pentland Hills, Scotland. Feral horses, though popularly called "wild" horses, are not truly wild; their ancestors were domesticated animals.
Main articles: Feral horse and Mustang (horse)

Horses which live in an untamed state but have ancestors who have been domesticated are not true "wild" horses; they are feral horses. The best known examples of feral horses are the "wild" horses of the American west. When Europeans reintroduced the horse to the Americas, beginning with the arrival of the Conquistadors in the 15th century, some horses escaped and formed feral herds known today as Mustangs. The Australian equivalent to the mustang is the brumby, descendants of the horses let loose in Australia by English settlers.[8] In Spain, the free-ranging feral horse is known as Sorraia. There are also isolated populations of feral horses in a number of places, including Sable Island off the coast of Nova Scotia, and Assateague Island off the coast of Virginia. Some of these horses are said to be the descendants of horses who managed to swim to land when they were shipwrecked. Others may have been deliberately brought to various islands by settlers and either left to reproduce freely, or abandoned when assorted human settlements failed. While these are often referred to as "wild" horses, they are not truly "wild" in the biological sense of having no domesticated ancestors.

[edit] References

  1. ^ "Przewalski's Horse," Smithsonian National Zoological Park, accessed June 25, 2006
  2. ^ "An extraordinary return from the brink of extinction for worlds last wild horse" ZSL Living Conservation, December 19, 2005.
  3. ^ The American Museum of Natural History When Is a Wild Horse Actually a Feral Horse?
  4. ^ "Ice Age Horses May Have Been Killed Off by Humans" National Geographic News, May 1, 2006.
  5. ^ a b Colin Groves, 1986, "The taxonomy, distribution, and adaptations of recent Equids," In Richard H. Meadow and Hans-Peter Uerpmann, eds., Equids in the Ancient World, volume I, pp. 11-65, Wiesbaden: Ludwig Reichert Verlag.
  6. ^ Van Vuure, C. 2005. Retracing the Aurochs: History, Morphology and Ecology of an Extinct Wild Ox. Pensoft Publishers. Sofia-Moscow.
  7. ^ International Commission on Zoological Nomenclature. 2003. Opinion 2027 (Case 3010). Usage of 17 specific names based on wild species which are pre-dated by or contemporary with those based on domestic animals (Lepidoptera, Osteichthyes, Mammalia): conserved. Bull.Zool.Nomencl., 60:81-84.
  8. ^ Nimmo, D. G., & Miller, K. K. (2007) Ecological and human dimensions of management of feral horses in Australia: A review. Wildlife Research 34: 408–417.

[edit] See also