Przewalski's horse (pronounced pron.: // shə-VAL-skee or // zə-VAHL-skee; Polish: [pʂɛˈvalski]; Equus ferus przewalskii, Mongolian: Тахь, takhi) or Dzungarian horse, is a rare and endangered subspecies of wild horse (Equus ferus) native to the steppes of central Asia, specifically Mongolia. At one time extinct in the wild (in Mongolia, the last wild Przewalski's horses had been seen in 1966), it has been reintroduced to its native habitat in Mongolia at the Khustain Nuruu National Park, Takhin Tal Nature Reserve, and Khomiin Tal. The taxonomic position is still debated, and some taxonomists treat Przewalski's horse as a species, Equus przewalskii.
Common names for this equine include Asian wild horse, Przewalski's wild horse, Mongolian wild horse, and tahki. Historical but obsolete names include true tarpan and Mongolian tarpan. The horse is named after the Russian geographer and explorer Nikolai Przhevalsky.
Most "wild" horses today, such as the American Mustang or the Australian Brumby, are actually feral horses descended from domesticated animals that escaped and adapted to life in the wild. In contrast, Przewalski's horse has never been successfully domesticated and remains a truly wild animal today. Przewalski's horse is one of three known subspecies of Equus ferus, the others being the domesticated horse, Equus caballus and the extinct tarpan (Equus ferus ferus). The Przewalski's horse is considered the only remaining truly wild "horse" in the world and may be the closest living wild relative of the domesticated horse. There are still a number of other wild equines, including three species of zebra and various subspecies of the African wild ass, onager (including the Mongolian wild ass) and kiang.
The Przewalski's horse was described in 1881 by L. S. Poliakov. The taxonomic position of Przewalski's horse has always been problematic and no consensus exists whether it is a full species (Equus przewalskii), a subspecies of the wild horse (Equus ferus przewalskii), or even a sub-population of the horse (Equus ferus). Studies using DNA have been inconclusive, in part due to crossing domestic horses into the Przewalski's horse as well as the limited genetic variation present in the founder population of the Przewalski's horse. A 2009 molecular study using ancient DNA recovered from archaeological finds like bones and teeth places the Przewalski's horse in the middle of the domesticated horses, but 2011 mitochondrial DNA analysis suggests that the Przewalski and the modern domestic horse diverged some 160,000 years ago. The karyotype of the domestic horse differs from that of Przewalski’s horse by an extra chromosome pair either because of the ﬁssion of domestic horse chromosome 5 in Przewalski’s horse or fusion of Przewalski’s horse chromosomes 23 and 24 in the domestic horse. In comparison, the chromosomal differences between domestic horses and zebras include numerous translocations, fusions, and inversions. Przewalski’s horse is known to have the highest diploid chromosome number among all equine species. Przewalski’s horse can interbreed with the domestic horse and produce fertile offspring (65 chromosomes).
All Przewalski horses in the world are descended from nine of the 31 horses in captivity in 1945. These nine horses were mostly descended from approximately 15 captured around 1900. A cooperative venture between the Zoological Society of London and Mongolian scientists has resulted in successful reintroduction of these horses from zoos into their natural habitat in Mongolia; and as of 2011 there is an estimated free-ranging population of over 300 in the wild. The total number of these horses according to a 2005 census was about 1,500.
Przewalski's horse is stockily built in comparison to domesticated horses, with shorter legs. Typical height is about 13 hands (52 inches, 132 cm), length is about 2.1 m (6 ft 11 in). They weigh around 300 kilograms (660 lb). The coat is generally dun in color with pangaré features, varying from dark brown around the mane (which stands erect) to pale brown on the flanks and yellowish-white on the belly and around the muzzle. The legs of Przewalski's horse are often faintly striped, also typical of primitive markings. The tail is about 90 cm (35.43 in) long, with a longer dock and shorter hair than seen in domesticated horses.
The Przewalski's horse has 66 chromosones, compared to 64 in all other horse species.
In the wild, Przewalski's horses live in small, permanent family groups consisting of one adult stallion, one to three mares, and their common offspring. Offspring stay in the family group until they are no longer dependent, usually at two or three years old. Bachelor stallions, and sometimes old stallions, join bachelor groups. Family groups can join together to form a herd that move together.
The patterns of their daily lives exhibit horse behavior similar to that of feral horse herds. Stallions herd, drive and defend all members of their family, while the mare often displays leadership in the family. Stallions and mares stay with their preferred partner for years.
Horses maintain visual contact with their family and herd at all times and have a host of ways to communicate with one another, including vocalizations, scent marking, and a wide range of visual and tactile signals. Each kick, groom, tilt of the ear, or other contact with another horse is a means of communicating. This constant communication leads to complex social behaviors among Przewalski's horses.
In the 15th century, Johann Schiltberger recorded one of the first European sightings of the horses in the journal of his trip to Mongolia as a prisoner of the Mongol Khan. The horse is named after the Russian colonel Nikolai Przhevalsky (1839–1888) (the name is of Polish origin and "Przewalski" is the Polish spelling). He was the explorer and naturalist who first described the horse in 1881, after having gone on an expedition to find it, based on rumors of its existence. Many of these horses were captured around 1900 by Carl Hagenbeck and placed in zoos. As noted above, about twelve to fifteen reproduced and formed today's population.
The native population declined in the 20th century due to a combination of factors, with the wild population in Mongolia dying out in the 1960s. The last herd was sighted in 1967 and the last individual horse in 1969. Expeditions after this failed to locate any horses, and the species had been designated "extinct in the wild" for over 30 years.
After 1945 only two captive populations in zoos remained, in Munich and in Prague. The most valuable group, in Askania Nova, Ukraine, was shot by German soldiers during World War II occupation, and the group in the United States had died out.
By the end of the 1950s, only 12 individual Przewalski's horses were left in the world.
In 1977, the Foundation for the Preservation and Protection of the Przewalski horse was founded in Rotterdam, the Netherlands, by Jan and Inge Bouman. The Foundation started a program of exchange between captive populations in zoos throughout the world to reduce inbreeding, and later began a breeding program of its own. As a result of such efforts, the extant herd has retained a far greater genetic diversity than its genetic bottleneck made likely.
In 1992, sixteen horses were released into the wild in Mongolia, followed by additional animals later on. One of the areas to which they were reintroduced became Khustain Nuruu National Park in 1998. Another reintroduction site is Great Gobi B Strictly Protected Area, located at the fringes of the Gobi desert. Lastly, in 2004 and 2005, 22 horses were released by the Association Takh to a third reintroduction site in the buffer zone of the Khar Us Nuur National Park, in the northern edge of the Gobi ecoregion.
The reintroduced horses successfully reproduced, and the status of the animal was changed from "extinct in the wild" to "endangered" in 2005. On the IUCN Red List, they were reclassified from "extinct in the wild" to "critically endangered" after a reassessment in 2008 and from "critically endangered" to "endangered" after a 2011 reassessment.
Preservation efforts 
While dozens of zoos worldwide have Przewalski's horses in small numbers, there are also specialized reserves dedicated primarily to the species.
The world's largest captive breeding program for Przewalski's horses is at the Askania Nova preserve in Ukraine. Several dozen Przewalski's horses were also released in the area evacuated after the Chernobyl accident, which now serves as a deserted de facto natural preserve. An intensely researched population of free-ranging animals was also introduced to the Hortobágy puszta in Hungary; data on social structure, behavior and diseases gathered from these animals is used to improve the Mongolian conservation effort.
Several American zoos also collaborated in breeding Equus ferus przewalskii from 1979 to 1982. Recent advances in equine reproductive science in the United States also have potential to further preserve and expand the gene pool. In October 2007, scientists at the Smithsonian Institution's National Zoo successfully reversed a vasectomy on a Przewalski's horse — the first operation of its kind on this species and possibly the first ever on any endangered species. While normally a vasectomy may be performed on an endangered animal under limited circumstances, particularly if an individual has already produced many offspring and its genes are overrepresented in the population, scientists realized the animal in question was one of the most genetically valuable Przewalski's horses in the North American breeding program.
Le Villaret, located in the Cevennes National Park in southern France and run by the Association Takh, is a breeding site for Przewalski Horses that was created to allow the free expression of natural Przewalski's horse behaviors. Eleven zoo-born horses were brought to Le Villaret in 1993. Horses born there are adapted to life in the wild: they are free to choose their own mates and must forage on their own. Such a unique breeding site was necessary to produce the individuals that were reintroduced to Mongolia in 2004 and 2005. In 2012 there were 39 individuals at Le Villaret.
The Przewalski's Horse Reintroduction Project of China was initiated in 1985 when 11 wild horses were imported from overseas. After more than two decades of effort, the Xinjiang Wild Horse Breeding Centre has bred a large number of the horses, of which 55 were released into the Kalamely Mountain area. The animals quickly adapted to their new environment. In 1988, six foals were born and survived, and by 2001 there were over 100 horses at the centre.
See also 
- Mongolian horse (domestic)
- Boyd, L. & King, S. R. B. (2011). "Equus ferus ssp. przewalskii". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved 24 June 2012.
- "The Takhi". International Takhi-Group. Retrieved 25 October 2010.
- Grubb, P. (2005). "Order Perissodactyla". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 630-631. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Ridgeway, William (1908). "Environment and race". The Geographical Journal (Royal Geographical Society.) 32 (4): 405–412. doi:10.2307/1776930. JSTOR 1776930., page 407
- Lau, Allison; Lei Peng, Hiroki Goto, Leona Chemnick, Oliver A. Ryder, Kateryna D. Makova (2009). "Horse Domestication and Conservation Genetics of Przewalski’s Horse Inferred from Sex Chromosomal and Autosomal Sequences". Mol. Biol. Evol. 26 (1): 199–208. doi:10.1093/molbev/msn239. PMID 18931383.
- Kavar, Tatjana; Peter Dovč (2008). "Domestication of the horse: Genetic relationships between domestic and wild horses". Livestock Science 116: 1–14. doi:10.1016/j.livsci.2008.03.002.
- Cai, Dawei; Zhuowei Tang, Lu Han, Camilla F. Speller, Dongya Y. Yang, Xiaolin Ma, Jian’en Cao, Hong Zhu, Hui Zhou (2009). "Ancient DNA provides new insights into the origin of the Chinese domestic horse". Journal of Archaeological Science 3 (3): 835–842. doi:10.1016/j.jas.2008.11.006.
- O A Ryder, A R Fisher, B Schultz, S Kosakovsky Pond, A Nekrutenko, K D Makova. "A massively parallel sequencing approach uncovers ancient origins and high genetic variability of endangered Przewalski's horses". Genome Biology and Evolution. 2011
- Boyd, Lee (1994). "Przewalski's Horse". p. 1.
- "Another leap towards the Barometer of Life". International Union for the Conservation of Nature. 10 November 2011. Archived from the original on 15 November 2011.
- "An extraordinary return from the brink of extinction for worlds last wild horse". ZSL Living Conservation. 19 December 2005. Archived from the original on 12 February 2012.
- National Zoo information on Przewalski's horse
- Gaddy, L. L. (2005). "Biodiversity: Przewalski's Horse, Edna's Trillium, the Giant Squid, and Over 1.5 Million Other Species". p. 6.
- Feh, C., 2005. Relationships and communication in socially natural horse herds. In: The Domestic Horse: the Evolution, Development and Management of its Behaviour. Ed. by Daniel Mills & Sue McDonnell, Cambridge University Press.
- Breeds of Livestock - Przewalski Horse
- O. A. Ryder et al, ibid
- IUCN Red List - Equus ferus
- Mulvey, Stephen (April 20, 2006). "Wildlife defies Chernobyl radiation". BBC News. Retrieved October 3, 2007.
- Rydera, Oliver A.; Wedemeyera, Elizabeth A. (April 1982). "Cooperative breeding programme for the Mongolian wild horse Equus przewalskii in the United States". Biological Conservation 22 (4). Science Direct. pp. 259–271. Retrieved 24 February 2010.
- Zongker, Brett (17 June 2008). "Rare horse gets reverse vasectomy". Associated Press (Today.com / NBC News).
- Przewalski's Horse - the last wild horse, http://www.takh.org
- Boyd, Lee and Katherine A. Houpt. (1994). Przewalski's Horse: The History and Biology of an Endangered Species. Albany, New York: State University of New York Press. 10-ISBN 0-7914-1889-8; 13-ISBN 978-0-7914-1889-5; OCLC 28256312
- Forestry Commission. 2004. FC Wales turns clock back thousands of years with 'wild' solution to looking after ancient forest site. News release, No: 7001, September 16, 2004. 
- 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. .
- Ishida, Nobushige; et al. (1995). "Mitochondrial DNA sequences of various species of the genus Equus with special reference to the phylogenetic relationship between Przewalskii's wild horse and domestic horse". Journal of Molecular Evolution 41 (2): 180–188. doi:10.1007/BF00170671. PMID 7666447.
- Jansen, Thomas; et al. (2002). "Mitochondrial DNA and the origins of the domestic horse". PNAS 99 (16): 10905–10910. doi:10.1073/pnas.152330099. PMC 125071. PMID 12130666.
- King, S. R. B.; Gurnell, J. (2006). "Scent-marking behaviour by stallions: an assessment of function in a reintroduced population of Przewalski horses (Equus ferus przewalskii)". Journal of Zoology 272 (1): 30–36. doi:10.1111/j.1469-7998.2006.00243.x.
- Wakefield, S., Knowles, J., Zimmermann, W. and Van Dierendonck, M. 2002. "Status and action plan for the Przewalski's Horse (Equus ferus przewalski)". In: P.D. Moehlman (ed.) Equids: Zebras, Asses and Horses. Status Survey and Conservation Action Plan, pp. 82–92. IUCN/SSC Equid Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK. 
- Wilford, John Noble (October 11, 2005). "Foal by Foal, the Wildest of Horses Is Coming Back". New York Times.
- Cao Jie, Przewalski's Horse Reintroduction Project of China
- Przewalski's Horse - Equus ferus przewalskii; IUCN/SSC Equid Specialist Group; Species Survival Groups ()
Further reading 
- Heptner, V. G. ; Nasimovich, A. A. ; Bannikov, A. G. ; Hoffman, R. S. (1988) Mammals of the Soviet Union, Volume I, Washington, D.C. : Smithsonian Institution Libraries and National Science Foundation