Przewalski's horse

Przewalski's horse
Przewalski's horse
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Genus: Equus
Subgenus: E. (Equus)
Species: E. ferus
Subspecies: E. f. przewalskii
Trinomial name
Equus ferus przewalskii
(L. S. Poliakov, 1881)
Przewalski's horse range
(reintroduced)
Synonyms

hagenbecki Matschie, 1903
prjevalskii Ewart, 1903
typicus Max Hilzheimer, 1909

Przewalski's horse (pronounced /ʃəˈvælski/ shə-VAL-skee or /pʃəˈvælski/ pshə-VAL-skee;[2] Khalkha Mongolian: тахь, takhi; Ak Kaba Tuvan: [daɣə//daɢə] dagy; Polish: [pʂɛˈvalskʲi]; Equus ferus przewalskii)[3] or Dzungarian horse, is a rare and endangered subspecies of wild horse (Equus ferus) native to the steppes of central Asia.[4] 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.[1] The taxonomic position is still debated, and some taxonomists treat Przewalski's horse as a species, Equus przewalskii.

Common names for this equine include takhi,[5] Asian wild horse and Mongolian wild horse,[6] The horse is named after the Russian geographer and explorer Nikolay 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 domesticated and remains the only truly wild horse in the world today. Przewalski's horse is one of three known subspecies of Equus ferus, the others being the domesticated horse Equus ferus caballus, and the extinct tarpan Equus ferus ferus. 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.

Taxonomy

The Przewalski's horse was described in 1881 by L. S. Poliakov, although the taxonomic position of Przewalski's horse remains controversial 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 domestic horse (Equus ferus caballus).[7][8][9]

Lineage

The date estimated for the evolutionary divergence of a domestic lineage from a wild one does not necessarily indicate the start of the domestication process but it does provide an upper boundary. The divergence of the domestic horse from the lineage that lead to the modern Przewalski’s horse is estimated at 45,000 YBP[10][11] but the archaeological record indicates 5,500 YBP.[10][12] The variance could be due to the modern wild population not being the direct ancestor of the domestic one, or the impact of a split due to climate, topography, or other environmental changes. The divergence time does not imply domestication during this specific period.[10]

Earlier DNA sequencing studies had been done to test whether or not the Przewalski horse is the primogenitor of domestic horses, but it was found that they are not. If Przewalski horses were indeed the ancestors of domesticated horses, those sequences, too would have been found within the Przewalski horse sequences. The DNA was then tested the other way as well; domestic horse sequences were checked for Przewalski horse sequences, and were found to contain none. This puts to rest the theory that Przewalski horses were derived from domestic horses.[13] Studies of the DNA diversity within the Przewalski horses have been done to see how successful their reintroduction into the wild may be. Studies have shown through multidimensional scaling analyses that tight grouping occurs within most horse breeds, close grouping between related breeds, and far less grouping between mixed breeds. The Przewalski horse and the domesticated horse showed a close relationship through pairwise genetic distance and multidimensional scaling analyses showing that the Przewalski horse is very closely related to the domesticated horse.

A 2009 molecular study using ancient DNA recovered from archaeological finds places the Przewalski's horse in the middle of the domesticated horses,[9] but 2011 mitochondrial DNA analysis suggests that the Przewalski and the modern domestic horse diverged some 160,000 years ago.[14] An analysis based on whole genome sequencing and calibration with DNA from old horse bones gave a divergence date of 38–72 thousand years ago.[15] 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).[7]

Population

Every Przewalski horse presently living is descended from 9 of the 13 horses captured in 1945.[16] Two of these were hybrids, one sired from a wild horse stallion and domestic mare and the other from a wild stallion and a tarpan mare. These 13 horses were descended in turn 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.[17] From a population of 13 horses held in captivity in 1945, the total number by the early 1990s was over 1,500.[18]

A population introduced in 1998 exists in the Chernobyl Exclusion Zone protected from interference by humans, and is thought to be increasing in size.[19]

Reproduction

Przewalski females are able to give birth at the age of three and have a gestation period of about 11 to 12 months. Their reproduction process is seasonal and in Mongolia the season is towards the end of either May, June, or July. Mating stallions do not start looking for mating partners until the age of five. Instinctively, the stallion will look to create his own group of mares or else wander until he finds a group with its own leader. If the stallion finds a group of mares with its own leader, the stallion will usually fight the other leader stallion of the group. The mares will adjust and follow the victor. After birth, the foal can stand almost immediately (only taking about an hour or so) and can walk on its own. The foals drink milk from the mother mare.

Characteristics

Przewalski's horse is stockily built in comparison to domesticated horses, with shorter legs. Typical height is about 12–14 hands (48–56 inches, 122–142 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.[20] The tail is about 90 cm (35.43 in) long, with a longer dock and shorter hair than seen in domesticated horses.

The hooves of the Przewalski's horse are longer in the back and have significantly thicker sole horn than feral horses. This is beneficial as it improves the performance of the hooves.

The Przewalski's horse has 66 chromosomes, compared to 64 in all other horse species.[21]

Behavior

Przewalski's horses.
Main article: Horse behavior

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 moves 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. While behavioral synchronization is high among mares, stallions other than the main harem stallion are generally less stable in this respect.

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.[22]

Diet

The Przewalski horse's diet consists mostly of vegetation. There are many plant species in a typical Przewalski horse environment including: Elymus repens, Carex spp., Fabaceae and Asteraceae.[23] While the horses eat a variety of different plant species, they tend to favor one species during a specific time of the year. In other words, the Przewalski horses have seasonal food preferences. In the springtime, Przewalski horses favor Elymus repens, Corynephorus canescens, Festuca valesiaca and Chenopodium album. In early summer they favor Dactylis glomerata and Trifolium and in late summer, they gravitate towards Elymus repens and Vicia cracca.[23] In winter, for example, the horses eat Salix spp., Pyrus communis, Malus sylvatica, Pinus sylvestris, Rosa spp., and Alnus spp. Additionally, Przewalski horses may dig for Festuca spp., Bromus inermis and Elymus repens that grow beneath the ice and snow. The Przewalski horse’s winter diet is very similar to the diet of domestic horses.[23] Studies have suggested that in the wintertime, Przewalski horses experience hypodermis. Hypodermis is a condition in which one’s metabolic rate slows down. This means that in the winter time, Przewalski horse’s process their food more slowly than they do during other times of the year. Looking at the species diet overall, however, Przewalski horses most often eat Elymus repens, Trifolium pratense, Vicia cracca, Poa trivialis, Dactylis glomerata and Bromus inermis.[23]

Water, along with grassy vegetation, is another major component of the Przewalski horse's diet. A study, conducted by K.M. Scheibe and a team of scientists, documented the water consumption of 12 female Przewalski horses that were living in a semireserve over a course of 17 months. Their results show that, on average, a Przewalski horse drinks between 2.4 and 8.3 liters of water a day, which is less than the amount of water a domestic horse drinks daily. In fact, the Przewalski horse that consumed the most water in the study drank on average 8.6 liters of water a day. This almost equals the lowest amount of water consumption for a domestic horse which is 8.4 liters a day.

History

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.[24] 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.

Head shot, showing convex profile.

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. Competition with livestock, hunting, capture of foals for zoological collections, military activities, and harsh winters recorded in 1945, 1948 and 1956 are considered to be the main causes of the decline in the Przewalski's horse population. By the end of the 1950s, only 12 individual Przewalski's horses were left in the world.[25]

Przewalski's horses.

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.[25]

Since 1986, Chinese researchers have bred Prezewalski's horses in captivity, with the program seeing over twenty years of success.

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. In the winter of 2009-2010, one of the worst "dzud" or snowy winter conditions ever hit Mongolia. The population of the Prezewalski's horse in the Great Gobi B SPA was drastically affected, providing clear evidence of the risks associated with reintroducing small and sequestered species in unpredictable and unfamiliar environments.

Since 2011, Prague Zoo has transported twelve horses to Mongolia in three rounds, in cooperation with partners (Czech Air Force, European Breeding Programme for Przewalski's Horses, Association pour de cheval du Przewalski : Takh, Czech Development Agency, Czech Embassy in Mongolia and others) and it plans to continue to return horses to the wild in the future. In the framework of the project Return of the Wild Horses it sustains its activities by supporting local inhabitants. The Zoo has the longest uninterrupted history of breeding of Przewalski's horses in the world and keeps the studbook of this species.

The reintroduced horses successfully reproduced, and the status of the animal was changed from "extinct in the wild" to "endangered" in 2005.[18] On the IUCN Red List, they were reclassified from "extinct in the wild" to "critically endangered" after a reassessment in 2008[26] and from "critically endangered" to "endangered" after a 2011 reassessment.[17]

Conservation efforts

Close-up image.
Przewalski's horses in Cologne Zoo Germany

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 nature reserve.[27] In Chernobyl, the population reproduced at a high rate, reaching up to 200 individuals until poachers decreased their number to just 60 in recent years.[28] As of 2011, it was estimated that only 30–40 individuals remained. An intensely researched population of free-ranging animals was also introduced to the Hortobágy National Park 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.[29] 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.[30] The first birth by artificial insemination occurred on July 27, 2013 at the Smithsonian Conservation Biology Institute.[31][32]

Le Villaret, located in the Cevennes National Park in southern France and run by the Association Takh, is a breeding site for Przewalski's 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.[33]

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. As of 2013, the center hosted 127 horses divided into 13 breeding herds and three bachelor herds.

Reintroductions organized by western European countries started in 1990s. These were later stopped, mostly for financial reasons. Prague Zoo started a new cycle of transporting horses to the wild, which, with the support of public and many strategic partners, continues today.

See also

Notes

  1. 1 2 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 June 24, 2012.
  2. ↑ Dictionary.reference.com
  3. ↑ "The Takhi". International Takhi-Group. Archived from the original on July 19, 2012. Retrieved October 25, 2010.
  4. ↑ 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. 630–631. ISBN 978-0-8018-8221-0. OCLC 62265494.
  5. ↑ International Takhi Group. "Takhi: Holy Animal of Mongolia". International Takhi Group. Retrieved August 13, 2016.
  6. ↑ "Equus ferus ssp. przewalskii". International Union for Conservation of Nature (IUCN) Redlist. Retrieved August 13, 2016.
  7. 1 2 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.
  8. ↑ 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.
  9. 1 2 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.
  10. 1 2 3 Machugh, David E.; Larson, Greger; Orlando, Ludovic (2016). "Taming the Past: Ancient DNA and the Study of Animal Domestication". Annual Review of Animal Biosciences. 5. doi:10.1146/annurev-animal-022516-022747.
  11. ↑ Der Sarkissian C, Ermini L, Schubert M, Yang MA, Librado P, et al. 2015. Evolutionary genomics and conservation of the endangered Przewalski’s horse. Curr. Biol. 25:2577–83
  12. ↑ Outram AK, Stear NA, Bendrey R, Olsen S, Kasparov A, et al. 2009. The earliest horse harnessing and milking. Science 323:1332–35
  13. ↑ Goto, Hiroki; Ryder, Oliver A.; Fisher, Allison R.; Schultz, Bryant; Pond, Sergei L. Kosakovsky; Nekrutenko, Anton; Makova, Kateryna D. (January 1, 2011). "A Massively Parallel Sequencing Approach Uncovers Ancient Origins and High Genetic Variability of Endangered Przewalski's Horses". Genome Biology and Evolution. 3: 1096–1106. doi:10.1093/gbe/evr067. ISSN 1759-6653. PMC 3194890Freely accessible. PMID 21803766.
  14. ↑ 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
  15. ↑ Orlando, L.; Ginolhac, A. L.; Zhang, G.; Froese, D.; Albrechtsen, A.; Stiller, M.; Schubert, M.; Cappellini, E.; Petersen, B.; Moltke, I.; Johnson, P. L. F.; Fumagalli, M.; Vilstrup, J. T.; Raghavan, M.; Korneliussen, T.; Malaspinas, A. S.; Vogt, J.; Szklarczyk, D.; Kelstrup, C. D.; Vinther, J.; Dolocan, A.; Stenderup, J.; Velazquez, A. M. V.; Cahill, J.; Rasmussen, M.; Wang, X.; Min, J.; Zazula, G. D.; Seguin-Orlando, A.; Mortensen, C. (2013). "Recalibrating Equus evolution using the genome sequence of an early Middle Pleistocene horse". Nature. 499 (7456): 74–78. doi:10.1038/nature12323. PMID 23803765.
  16. ↑ Boyd, Lee (1994). Przewalski's Horse. p. 1.
  17. 1 2 "Another leap towards the Barometer of Life". International Union for the Conservation of Nature. November 10, 2011. Archived from the original on November 15, 2011.
  18. 1 2 "An extraordinary return from the brink of extinction for worlds last wild horse". ZSL Living Conservation. December 19, 2005. Archived from the original on February 12, 2012.
  19. ↑ Wendle, John. "Animals Rule Chernobyl 30 Years After Nuclear Disaster". National Geographic. Retrieved May 2, 2016.
  20. ↑ National Zoo information on Przewalski's horse
  21. ↑ Gaddy, L. L. (2005). Biodiversity: Przewalski's Horse, Edna's Trillium, the Giant Squid, and Over 1.5 Million Other Species. p. 6.
  22. ↑ 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.
  23. 1 2 3 4 Diet of the Przewalski's horse Equus przewalskii in the Chernobyl exclusion zone Archived October 29, 2013, at the Wayback Machine. Kateryna Slivinska and Grzegorz Kopij, pages 841-847, July 2011
  24. ↑ Breeds of Livestock - Przewalski Horse Archived October 17, 2014, at the Wayback Machine.
  25. 1 2 O. A. Ryder et al, ibid
  26. ↑ IUCN Red List - Equus ferus
  27. ↑ Mulvey, Stephen (April 20, 2006). "Wildlife defies Chernobyl radiation". BBC News. Retrieved October 3, 2007.
  28. ↑ Gill, Victoria (July 27, 2011). "Chernobyl's Przewalski's horses are poached for meat". BBC Nature. Retrieved May 2, 2016.
  29. ↑ Rydera, Oliver A.; Wedemeyera, Elizabeth A. (April 1982). "Cooperative breeding programme for the Mongolian wild horse Equus przewalskii in the United States". Biological Conservation. Science Direct. pp. 259–271. Retrieved February 24, 2010.
  30. ↑ Zongker, Brett (June 17, 2008). "Rare horse gets reverse vasectomy". Today.com / NBC News. Associated Press.
  31. ↑ "Przewalski's Horse Foal Born via Artificial Insemination". TheHorse.com. August 2, 2013.
  32. ↑ Shenk, Emily (August 5, 2013). "First Przewalski's Horse Born Via Artificial Insemination". National Geographic. Retrieved August 14, 2013.
  33. ↑ Przewalski's Horse - the last wild horse, Association Takh

References

Further reading

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