Przewalski's Horse
Equus ferus przewalskii
CR
Taxonomic Authority: Boddaert, 1785
No synonyms available
Common names
Asian wild horse - English (Primary)
Mongolian wild horse - English
Przewalski's horse - English
Takh - Mongolian
Ye-ma - Chinese
Although wild horses (of which Przewalski's horse Equus ferus przewalskii is the only living representative) can hybridize with domestic horses to produce fertile offspring (Ryder et al. 1978; Trommerhausen-Smith et al. 1979), the existence of 2n=66 chromosomes in Przewalski's horse identifies it as being more different from its domestic relatives (2n=64) than are any two breeds of domestic horse (Ryder 1994). Mitochondrial DNA research has shown that the Przewalski's horse is not ancestral to modern domestic horses (Vila et al 2001). Przewalski's horses also show a number of other consistent differences in their appearance: the mane is short and erect in most horses that are in good body condition, forelocks are close to nonexistent; the upper part of the tail has short guard hairs, unlike domestic horses, that have long, falling manes and long guard hairs all over the tail; a dark dorsal stripe runs from the mane down the back and dorsal side of the tail to the tail tuft; several dark stripes can be present on the carpus and, generally, the tarsus (Groves 1994). Przewalski's horses, contrary to domestic horses, shed their tail and mane hair once per year.
Other studies of the genetic differences between Przewalski's and domestic horses have indicated very little genetic distinction between them. Only four alleles at four separate serological marker loci have been identified as specific to Przewalski's horse (Bowling and Ryder 1987), the vast majority of blood protein variants are present in both Przewalski's and domestic horses and even the fastest evolving DNA region known in mammals (the mitochondrial DNA control region), does not show significant differences between the two types of horse (Ishida et al. 1995; Oakenfull and Ryder 1998). Thus it is clear that Przewalski's and domestic horses are very closely related and have in the past interbred, but the fixed chromosomal number difference between them indicates that they are distinct populations (Oakenfull et al. 2000).
General Information
Distribution
The last wild population of Przewalski's horses survived until recently in southwestern Mongolia and adjacent Gansu, Xinjiang, and Inner Mongolia (China). Wild horses were last seen in 1969, north of the Tachiin Shaar Nuruu in Dzungarian Gobi Desert in Mongolia (Paklina and Pozdnyakova, 1989).
Since the 1990s, reintroduction efforts have started in Mongolia, China, Kazakhstan and Ukraine; Mongolia is the only country where truly wild re-introduced populations exist within its historic range. Reintroductions in Mongolia began in Takhin Tal Nature Reserve in the Dzungarian Gobi Desert (9,000 km2) and Hustai National Park in Mongol Daguur Steppe (570 km2) in 1994 (King and Gurnell, 2005). A third reintroduction site, Khomiin Tal, (2,500 km2), in the Great Lakes Depression was established in 2004, as a buffer zone to the Khar Us Nuur National Park in Valley of the Lakes (C. Feh, pers. comm.).
All living wild horses belong to the subspecies Equus ferus przewalskii. The first visual account of Przewalski's-type wild horses date from more than 20,000 years ago. Rock engravings, paintings, and decorated tools dating from the late Gravetian to the late Magdalenian (20,000-9,000 BC), were discovered in caves in Italy, southern France, and northern Spain; 610 of these were horse figures (Leroi-Gourhan 1971). Many cave drawings in France show horses that look like Przewalski's horse (Mohr 1971). In prehistoric times, the species probably roamed widely over the steppes of central Asia, China, and Europe (Ryder 1990). The first written accounts originate from Tibet, recorded by the monk Bodowa, who lived around 900 AD. In the "Secret History of the Mongols", there is also a reference to wild horses that crossed the path of Chinggis Khaan during his campaign against Tangut in 1226, causing his horse to rear and throw him to the ground (Bokonyi 1974). That the wild horse was a prestigious gift, denoting its rarity or that it was difficult to catch, is shown by the presentation of a Przewalski's horse to the emperor of Manchuria by Chechen-Khansoloj-Chalkaskyden, an important Mongolian, circa 1630 (Zevegmid and Dawaa 1973). In a Manchurian dictionary of 1771, Przewalski's horse is mentioned as 'a wild horse from the steppe' (Dovchin 1961).
Przewalski's horse was not described in Linnaeus's 'Systema Naturae' (1758) and remained largely unknown in the West until first mentioned by John Bell, a Scottish doctor who travelled in the service of Tsar Peter the Great in 1719-1722 (Mohr 1971). His account of the expedition, A "Journey from St Petersburg to Peking", was published in 1763. Bell and subsequent observers all located horses known at that time within the area of 85°-97° E and 43°-50° N (Chinese-Mongolian border). Wild horses were reported again from what is now China by Colonel Nikolai Mikailovich Przewalski, an eminent explorer, at the end of the nineteenth century. He made several expeditions by order of Tsar Alexander the Second of Russia to central Asia, aiming to reach Tibet. While returning from his second expedition in central Asia, he was presented with the skull and hide of a horse shot about 80 km north of Gutschen on the Chinese-Russian border. The remains were examined at the Zoological Museum of the Academy of Science in St Petersburg by I.S. Poliakov, who concluded that they were a wild horse, which he gave the official name Equus przewalskii (Poliakov 1881). Further reports came from the brothers Grigory and Michael Grum-Grzhimailo, who travelled through western China from 1889-1890. In 1889, they discovered a group in the Gashun area and shot four horses: three stallions, and a mare. The four hides and the skulls of the three stallions, together with an incomplete skeleton, were sent back to the Zoological Museum in St Petersburg. They were able to observe the horses from a short distance and gave the following account: 'Wild horses keep in bands of no more than ten, each herd having a dominant stallion. There are other males, too, but they are young and, judging by the hide of the two-year old colt that we killed, the dominant male treats them very cruelly. In fact, the hide showed traces of numerous bites' (Grum-Grzhimailo 1982). Current scientific review of the taxonomy of wild equids (Groves 1986) places Przewalski's horse as a subspecies of Equus ferus.
Population
There are now approximately 325 free-ranging re-introduced and native-born Przewalski's horses in Mongolia (January 2008). All
Przewalski's horses alive today are descended from only 13 or 14 individuals, which were the nucleus of a captive breeding programme
(Bowling and Ryder 1987). Introgression of domestic horse blood happened not only in Halle (#229 dom.Mongol), but also in Askania Nova
(#175 Domina; Bowling, et al. 2003). Between 1992 and 2004, 90 captive-born horses were transported to the Takhin Tal/Gobi B reintroduction
site in Mongolia (ITG International Takhi Group, Zimmermann 2008). A further three males were translocated from Hustai National Park to
Takhin Tal in 2007 (Zimmermann 2008). There are currently 111 free-ranging horses in nine groups within this population (Zimmermann 2008,
Kaczensky and Walzer 2007). From 1992 to 2000, 84 horses were brought to Hustai National Park by the Foundation for the Preservation and
Protection of Przewalski's Horse and Mongolian Association for Conservation
of Nature and the Environment (MACNE) from reserves in Europe (King and Gurnell 2005). As of 1 January 2008 this population totaled
approximately 192 individuals in 24 harems with 33 bachelor males (Zimmerman 2008). A third reintroduction site was started in 2004 at
Seriin Nuruu in the Khomiin Tal buffer zone of the Khar Us Nuur National Park in western Mongolia (Association pour le cheval de Przewalski:
TAKH). Twenty-two individuals consisting of four pre-established families and one male bachelor group were brought from Le Villaret, France
between 2004 and 2005 (C. Feh pers. comm., Zimmermann 2008). For the reintroduced population in Mongolia mature individuals are those that
are five years of age, however individuals born in captivity do not count as mature until they have reproduced in the wild and that
offspring is at least five years old. As of 2006 there were 55 mature individuals in the wild (52 (M.F 26.26) in Hustai, 3 (1.2) in
Takhin Tal). In 2007 Hustai had 68 (33.35) mature individuals that h
ad been born in Mongolia and Takhin Tal had 11 (3.8).
In China, the Wild Horse Breeding Centre (WHBC) of the Department of Forestry at Kalameili Nature Reserve (KNR) in Xinjiang Uighur Autonomous Region has established a large captive population of approximately 123 Przewalski's horses (January 2008, Pantel et al 2006, Zimmermann et al. 2007). Since 2007 one harem group is roaming free on the Chinese side of the Dzungarian Gobi (Xinjiang); another 60 horses are roaming free during summer time but all return to the acclimatization pen during the winter (Zimmermann et al. 2007).
The history of population estimates and trends in Przewalski's horse has been described by Wakefield et al. (2002). Since the 'rediscovery' of the Przewalski's horse for western science, western zoos and wild animal parks became interested in this species for their collections. Several long expeditions were mounted to catch animals. Some expeditions came back empty-handed and some had only seen a glimpse of Przewalski's wild horse. It proved difficult to catch adult horses, because they were too shy and fast. Capture of foals, with possible killing of the adult harem members, was considered the only option (Bouman and Bouman 1994). Four expeditions that managed to catch live foals took place between 1897 and 1902. Fifty-three of these foals reached the west alive. Between the 1930s and the 1940s only a few Przewalski's horses were caught and most died. At least one mare was crossbred with domestic horses by the Mongolian War Ministry (Bouman and Bouman 1994).
Small groups of horses were reported through the 1940s and 1950s in an area between the Baitag-Bogdo ridge and the ridge of the Takhin-Shaar Nuruu (which, translated from Mongolian, means the "Yellow Mountain of the Wild Horse"), but numbers appeared to decline dramatically after World War II. The last confirmed sighting in the wild was made in 1969 by the Mongolian scientist N. Dovchin. He saw a stallion near a spring called Gun Tamga, north of the Takhin-Shaar Nuruu, in the Dzungarian Gobi (Paklina and Pozdnyakova 1989). Annual investigations by the Joint Mongolian-Soviet Expedition have since failed to find conclusive evidence for their survival in the wild (Ryder 1990). Chinese biologists conducted a survey in northeastern Xinjiang from 1980 to 1982 (covering the area of 88°-90° E and 41°31'-47°10' N) without finding any horses (Gao and Gu 1989). The last native wild populations have disappeared.
The number of living animals in the international studbook was 1872 in 2008. Of the 53 animals recorded in the studbook as having been brought into zoological collections in the west, only 12 contributed any genes to the current living population. Of these, 11 were brought into captivity between 1899-1902 and the last of them died in 1939. The twelfth founder was captured as a foal in 1947. The thirteenth founder was born in 1906 in Halle (Germany) to a wild-caught stallion and a domestic Mongolian mare, and the fourteenth founder is a female born in Askania Nova (Ukraine) to a Przewalski's horse stallion and a domestic female of a Tarpan type. Nevertheless, the current population is genetically very close to the original wild horses (Bowling et al. 2003). In addition to animals held in captivity and those already re-introduced, there have been a number of animals released into very large enclosures (reserves). The four largest are in Le Villaret (21.16; Massif Central, France), Buchara (19.17.1; Uzbekistan), the Hortobágy-National Park (45.44; Hungary), and the Chernobyl exclusion zone (32.35; Ukraine) (information as of January 2008, Zimmermann pers. com.).
Habitat and Ecology
Przewalski's horse formerly inhabited steppe and semi-desert habitats, as most of this range became degraded or was occupied
by livestock, the species became restricted to semi-desert habitats with limited water resources (Van Dierendonck and de Vries, 1996).
Lowland steppe vegetation was preferentially selected by horses at Hustai National Park and seasonal movements are affected by the
availability of the most nutritious vegetation (King and Gurnell, 2005).
Because the historic range is not precisely known, there has been much debate about the areas in which Przewalski's horses were last seen: was it merely a last refuge or was it representative of the typical/preferred habitat? The Mongolia Takhi Strategy and Plan Work Group (MTSPWG 1993) concluded that the historic range may have been wider but that the Dzungarian Gobi, where they were last seen, was not a marginal site to which the species retreated. Although grass and water are more available in other parts of Mongolia, these areas often have much harsher winters. Of all the wild equid species, Przewalski's horse is the one with the most eastern distribution and was most likely well-adapted to the arid steppe of the Dzungarian Gobi (Zimmermann 1999).
An alternative viewpoint of the desert-steppe controversy is that the Eurasian steppe should be considered the takhi's optimal habitat (Van Dierendonck and de Vries 1996). This would suggest that Przewalski's horses were forced into sub-optimal ranges such as the arid Gobi, as the more favourable steppe region was colonised by nomadic pastoralist people over several millennia. Studies of feral horses have shown that they are able to live and reproduce in semi-desert habitats but their survival and reproductive success is clearly sub-optimal compared to feral horses on more mesic grassland (Berger 1986). Van Dierendonck and de Vries (1996) suggest that the takhi is primarily a steppe herbivore that can survive under arid conditions when there is access to waterholes.
Threats
A number of causes have been cited for the final extinction of Przewalski's horses in Mongolia and China. Among these are significant
cultural and political changes (Bouman and Bouman 1994), hunting (Zhao and Liang 1992; Bouman and Bouman 1994), military activities
(Ryder 1993), climatic change (Sokolov et al. 1992), and competition with livestock and increasing land use pressure (Sokolov et al. 1992;
Ryder 1993; Bouman and Bouman 1994). Capture expeditions probably diminished the remaining Przewalski's horse populations by killing and
dispersing the adults (Van Dierendonck and de Vries 1996). The harsh winters of 1945, 1948, and 1956 probably had an additional impact on
the small population (Bouman and Bouman 1994). Increased pressure on, and rarity of waterholes in their last refuge should also be
considered as a significant factor contributing to their extinction (Van Dierendonck and de Vries 1996).
For the re-introduced populations, hybridization with domestic horses is the primary threat, accompanied by competition for resources with domestic horses and possibly other livestock. Wherever Przewalski's horses come into contact with domestic horses, there is a strong risk of hybridization and transmission of diseases. In Hustai National Park, it has been noted that overgrazing of the buffer-zone and continued pressure on the reserve are possible consequences of the enhanced economic activity in this area (Bouman 1998); however, the second phase of the project (1998-2003) paid much more attention to sustainable development of the buffer-zone. In the western section of the Gobi National Park (Gobi B), habitat degradation by nomads and military personnel and their livestock continues; there is no core zone here that is free from human influence all year round. Infectious diseases transmitted from domestic horses, notably Babesia equi, B. caballi and strangles (infection by Streptococcus equi), are a major threat to small re-introduced populations originating from zoos (Roberts et al. 2005; King & Gurnell, 2005). Predation on foals by wolves may account for a significant number of mortalities and constitutes a threat to the population growth and continued survival of this taxon (Wit and Bouman 2006, Kaczensky et al. 2004, Kaczensky and Walzer 2007).
There is concern over loss of genetic diversity after being reduced to a very small population and maintained in captivity for several generations. Sixty percent of the unique genes of the studbook population have been lost (Ryder 1994). Loss of founder genes is irretrievable and further losses must be minimised through close genetic management. Furthermore, inbreeding depression could become a population-wide concern as the population inevitably becomes increasingly inbred (Ballou 1994). However, correct management of the population can slow these losses significantly, as has been achieved since the organisation of the regional captive breeding programmes.
Conservation Measures
Przewalski's horse is legally protected in Mongolia. It is protected as Very Rare under part 7.1 of the Law of the Mongolian Animal
Kingdom (2000). Hunting has been prohibited since 1930, and the species is listed as Very Rare under the 1995 Mongolian Hunting
Law (MNE 1996). It is listed as Critically Endangered in both the 1987 and 1997 Mongolian Red Books (Shagdarsuren et al.
1987; MNE 1997), and in the Regional Red List for Mongolia (Clark et al. 2006). The taxon's entire re-introduced range in Mongolia is
within protected areas. It is listed on CITES Appendix I.
The following conservation measures are in place:
An International Studbook was produced in 1959, followed in the 1970s by establishment of the North American Breeders Group,
which developed into the Species Survival Plan for the Przewalski's horse. The European Endangered Species Programme for this
species was accepted in 1986. Many countries now cooperate in these programmes to minimise inbreeding and retain genetic
diversity in their horse populations.
There are three ongoing reintroduction sites in Mongolia.
There have been several workshops of stakeholders involved in the reintroduction of Przewalski's horse to Mongolia.
The Status and Action Plan for the Przewalski's horse (Equus ferus przewalskii) was produced in 2002 (see Wakefield et al.
2002), and provides a more detailed account of the history and ongoing conservation efforts surrounding the species.
All three reintroduction sites fully monitor are monitoring their populations and are integrating community livelihood support into their projects.
Conservation measures required
The health of wild and domestic horses should be monitored for disease (Roberts et al. 2005). Standardised techniques should
be used to monitor health, fecundity, mortality, habitat utilisation and social organisation of all populations (Wakefield et al. 2002),
and contact between Przewalski's horses and domestic horses should be kept to a minimum.
A single population management approach should be developed
Mongolia currently has the only wild population and an action plan is needed for the country.
The geneology of all horses in Mongolia should be establshed based on individual micro-satellite data to monitor inbreeding levels,
identify hybrids and plan for necessary movements of horses between re-introduction centres to maximise genetic diversity.
An authoritative government protocol for hybrids should be developed, to be established before hybridization occurs, and to be
made available in each re-introduction centre and to local people (King and Gurnell 2005).
Further communication and cooperation between all re-introduction centres would be beneficial.
Further training and post-graduate education of staff and biologists involved with this conservation work.
IUCN Red Listing
Red List Assessment: (using 2001 IUCN system) Critically Endangered (CR)
Red List Criteria: D1
Rationale for the Red List Assessment
Previously categorised as Extinct in the Wild from the 1960s until the most recent assessment in 1996, however, successful reintroductions have qualified this species for reassessment. The population is currently estimated to consist of fewer than 50 mature individuals free-living in the wild for the past five years. This taxon is threatened by hybridization with domestic horses, loss of genetic diversity, and disease. As the population size is small, Equus ferus przewalskii qualifies as Critically Endangered under Criterion D1.
Current Population Trend: Increasing (Date of Assessment: June 2008)
Tentative Name(s) of the Assessor(s): Boyd, L., Zimmermann, W., King, S. R. B.
Evaluator(s): Feh, C., Moehlman, P.
Notes:
Bibliography
Ballou, J. 1994. Population biology.. Przewalski's horse: the History and Biology of an Endangered Species, Boyd, L. and Houpt, K.A.,
State University of New York Press, Albany, New York
Berger, J., 1986, Wild Horses of the Great Basin, , The University of Chicago Press, Chicago and London
Bokonyi, S., 1974, The Przevalsky Horse., , Souvenir Press, London
Bouman, D.T. and Bouman, J.G., 1994, The history of Przewalski's horse. Przewalski's horse:the History and Biology of an Endangered Species, Boyd, L. and Houpt, K.A., State University of New York Press, Albany, New York
Bowling, A.T. and Ryder O.A., 1987, Genetic studies of blood markers in Przewalski's horse., Journal of Heredity, 75-80.
Bowling, A, T., Zimmermann, W., Ryder, O., Peto, S., Yasinetskaya, N. and Zharkikh, T, Genetic variation in Przewalski's horses, with special focus on the last wild caught mare, 231 Orlitza III. Cytogen. Genome Res. 101: 226-234.
Clark, E. L., Munkhbat, J., Dulamtseren, S., Baillie, J. E. M., Batsaikhan, N.,Samiya, R. and Stubbe, M. (compilers and editors) 2006. Mongolian Red List of Mammals. Regional Red List Series Vol. 1. Zoological Society of London, London.
Dovchin, N., 1961, The Przewalski horse in Mongolia., Equus, 22-27.
Gao, X. and Gu, J., 1989, The distribution and status of Equidae in China., Acta Theriologica Sinica, 269-274.
Groves, C.P., 1986, The taxonomy, distribution and adaptations of recent equids., Equids in the Ancient World, Meadow, R.H. and Uepermann, H.P., 11-65, Dr Ludwig Reichert Verlag, Wiesbaden
Groves, C.P., 1994, Morphology, habitat and taxonomy, Przewalski's horse:the History and Biology of an Endangered Species, Boyd, L. and Houpt, K.A., State University of New York Press, Albany, New York
Grum-Grzhimailo, G.E., 1982, The wild horse (Equus przewalskii). From the diary of a travel to China in 1889-1890 (translated by Aleinikov, P.) Niva 17.
Ishida, N., Oyunsuren, T., Mashima, S., Mukoyama, H. and Saitou, N., 1995, Mitochondrial DNA sequences of various species of the genus Equus with special reference to the phylogenetic relationship between Przewalski's wild horse and domestic horse., Journal of Molecular Evolution, 180-188.
Kaczensky, P. and Walzer, C. 2007. Landscape level research for the conservation of Asiatic wild ass in Mongolia. Report July 2007. www.takhi.org website. 21 pp.
Kaczensky, P., Enkhsaihan, N., Ganbaatar, O., Samjaa, R., von Wehrden, H. and Walzer, C., 2004, Takhis, khulans, wolves and vegetation - an ecosystem approach for takhi conservation, Mongolian Journal of Biological Sciences, 60.
King, S. R. B. and Gurnell, J., 2005, Habitat use and spatial dynamics of takhi introduced to Hustai National Park, Mongolia, Biological Conservation, 277-290.
Leroi-Gourhan, A., 1971, Préhistoire de l'art occidental., , Éditions D'art Lucien Mazenod, Paris Ministry of Nature and Environment (MNE), 1996, Biodiversity Conservation Action Plan for Mongolia, , The Ministry of Nature and Environment, Ulaanbaatar
Ministry of Nature and Environment (MNE), 1997, Mongolian Red Book, Shiirevdamba, Ts., Shagdarsuren, O., Erdenejav, G., Amgalan, Ts. & Tsetsegmaa, Ts. (eds), , ADMON Printing, Ulaanbaatar
Mohr, E., 1971, The Asiatic Wild Horse, , J.A. Allen and Co. Ltd., London MTSPWG (Mongolia Takhi Strategy and Plan Work Group), 1993, Recommendations for Mongolia's takhi strategy and plan, , Ministry of Nature and Environment, Mongolian Government, Ulaan Baatar
Oakenfull, E.A. and Ryder, O.A., 1998, Mitochondrial control region and 12S rRNA variation in Przewalski's horse (Equus Przewalskii), Animal Genetics, 456-459.
Oakenfull, E.A., Lim, H.N. and Ryder, O.A., 2000, A survey of equid mitochondrial DNA: implications for the evolution, genetic diversity and conservation of Equus, Conservation Genetics, 341-255.
Paklina, N. and Pozdnyakova, M.K., 1989, Why the Przewalski horses of Mongolia died out, Przewalski Horse, 30-34.
Pantel,N., Leimgruber,P., Zimmermann,W., Songer,M., and Cerny, A. 2006.Supporting Przewalski's Horse Reintroduction Efforts in China: Development of an Integrated Conservation Project with the Wild Horse Breeding Centre in Sinjiang Province, China. 39 pp.
Poliakov, I.S., 1881, Przewalski's horse (Equus przewalskii n. sp.)., Isvestia Russki Geographiceski obsch-va, St Petersburg, 1- 20.
Roberts, N., Walzer, C., Ruegg, S.R., Kaczensky, P., Ganbataar, O. and Stauffer, C., 2005, Pathological investigations of reintroduced Przewalski's horses (Equus caballus przewalskii) in Mongolia, Journal of Zoo and Wildlife Medicine, 273-285.
Ryder, O.A., 1990, Putting the wild horse back into the wild, Przewalski's Horse Global Conservation Plan, , Zoological Society of San Diego, Center for Reproduction of Endangered Species, San Diego
Ryder, O.A., 1993, Przewalski's horse: prospects for reintroduction into the wild, Conservation Biology, 13-15.
Ryder, O., 1994, Genetic studies of Przewalski's horses and their impact on conservation, Przewalski's horse:the History and Biology of an Endangered Species, Boyd, L. and Houpt, K.A., State University of New York Press, Albany, New York
Ryder, O., Epel, N.C. and Benirschke, K., 1978, Chromosome banding studies of the Equidae, Cytogenetics and Cell Genetics, 323- 350.
Shagdarsuren, O., Jigi, S., Tsendjav, D., Dulamtseren, S., Bold, A., Munkhbayar, Kh., Dulmaa, A., Erdenejav, G., Olziihutag, N., Ligaa, U. and Sanchir, Ch., 1987, Mongolian Red Book, Shagdarsuren, O., , Publishing House of the Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
Sokolov, V.E., Amarsanaa, G., Paklina, M.W., Posdnjakowa, M.K., Ratschkowskaja, E.I. and Chotoluu, N., 1992, Das Letzte Przewalskipferd areal und seine Geobotanische Characteristik, Proceedings of the 5th International Symposium on the Preservation of the Przewalski Horse, Seifert, S., 213-218, Zoologischer Garten Leipzig, Leipzig
Trommerhausen-Smith, A., Ryder, O. and Suzuki, Y., 1979, Bloodtyping studies of twelve Przewalski's horses, International Zoo Yearbook, 224-227.
Ulambayar, T., 2004, Integrating takhi re-introduction and park management with sustainable local livelihoods, Mongolian Journal of Biological Sciences, 63-64.
Van Dierendonck, M. and Wallis de Vries, M.F., 1996, Ungulate reintroductions: experiences with takhi or Przewalski horse (Equus ferus przewalskii) in Mongolia, Conservation Biology, 728-740.
Vila`.C., Leonard,J.A., Gotherstrom,A., Marklund,S., Sandberg,K., Lide, K., Wayne, R.K.,Ellegren, H. 2001. Widespread Origins of Domestic Horse Lineages, Science 291:474-477
Wakefield, S., Knowles, J, Zimmermann, W. and van Dierendonck, M., 2002, Status and action plan for the Przewalski's Horse (Equus ferus przewalskii), Equids: Zebras, Asses and Horses. Status Survey and Conservation Action Plan, Moehlman, P.D., 82-92, IUCN, Gland
Wit,P. and I. Bouman.2006. The Tale of the Przewalski's Horse coming home to Mongolia. KNNV Publishing, Utrecht, the Netherlands. 251 pp.
Zevegmid, D. and Dawaa, N., 1973, Die seltenen Großsäuger der Mongolischen Volksrepublik und ihr Schutz., Arch. Naturschutz u. Landschaftsforsch Berlin, 87-106.
Zhao, T. and Liang, G., 1992, On returning to its native place and conservating of the Przewalski horse., Proceedings of the 5th International Symposium on the Preservation of the Przewalski Horse, Seifert, S., 227-231, Zoologische Garten Leipzig, Leipzig
Zimmermann, W., 1999, Feasibility study, site selection and development of a reintroduction project of the Przewalski's horse (Equus ferus przewalskii) in the Dzungarian Gobi in Mongolia, Proceedings of the International Symposium Neuhaus/Solling, 21-23.4.1998: Natural and Man-made Landscape - History, Models and Perspectives for the Development of European Landscapes with Large Herbivores, Gerken, B. and Meyer, C.
Zimmermann, W., Leimgruber, P., Zukosky, M., 2008, Xinjiang Wild Horse Conservation Project. Trip Report November 2007, 33 pp.
Zimmermann, W. 2008.International Przewalski's Horse Studbook (EQUUS ferus przewalskii) SPARKS version (on cd) Cologne Zoo. January 2008. 39pp.
