Przewalski’s horse is the last remaining species of wild horse and inhabits the grasslands and deserts of China and Mongolia. This social species has never been domesticated, but can hybridize with the domestic horse. With less than 200 mature individuals, this species is considered endangered from overhunting.
Przewalski’s horse is stocky and looks very pony-like with short legs and a short neck. It stands at 120-146 centimeters, or 48-58 inches and has a body length of 2.1 meters, or 6.11 feet. Przewalski’s horse weighs 200-383 kilograms or 440-850 pounds. Its head is massive with a long face and a powerful jaw.
Like all horses, Przewalski’s horse is an odd-toed ungulate, a hoofed animal, or ungulate, which bears most of its weight on one of the fives toes: the third toe.
The Przewalski’s horse’s upper and lower incisors are used for cutting vegetation, while its many hypsodont cheek teeth are used for grinding. It has a dental formula of I ³⁄3, C ¹⁄1, P ³⁄3, M ³⁄3, = 36-42.
Like most prey species, Przewalski’s horse has large eyes located on the sides of the head and set far back in the skull. As such, the horse is able to see a wide field except directly behind it, even when its head is down while its are grazing or drinking.
Przewalski’s horse can detect smell and sound at great distances. Its ears are fairly long and erect, but can be moved for the localization of sounds. Its moods can be detected through changes in the positions of its ear, mouth, and tail.
Przewalski’s horse’s tan to reddish brown coloration helps it blend into its grassland and desert habitat. The horse has white on the belly, dark brown on the lower legs and mane, and a white muzzle.
Przewalski’s horse has a stiff, dark brown mane and grows a dense coat for very cold winters and sheds into a lighter coat for very hot summers. The horse sheds the hairs on its tail and mane all at once, unlike domestic horses that lose only a few hairs at a time. Przewalski’s horse’s tail length averages 90 centimeters, or 35.43 inches.
Lifespan for Przewalski’s horse is 20-25 years.
SHOULDER HEIGHT120-146 cm. / 48-58 in.
BODY LENGTH2.1 m. / 6.11 ft.
TAIL LENGTH90 cm. / 35.43 in.
BODY MASS200-383 kg. / 440-850 lbs.
DENTAL FORMULAI ³⁄3, C ¹⁄1, P ³⁄3, M ³⁄3, = 36-42
Przewalski’s horse was formally described as a novel species in 1881 by Ivan Semyonovich Polyakov, 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, along with two other subspecies, the domesticated horse (E. f. caballus), and the extinct tarpan (E. f. ferus)), or even a subpopulation of the domestic horse. Current scientific review of the taxonomy of wild equids places Przewalski’s horse as a subspecies of the extinct Equus ferus, known as the wild horse. The International Union for Conservation of Nature and Natural Resources (IUCN) currently classifies Przewalski’s horse as both a species (Equus ferus) and a subspecies (Equus ferus przewalskii), though all extant wild horses belong to the subspecies Equus ferus przewalskii.Although Przewalski’s horse (Equus ferus przewalskii) can hybridize with domestic horses (Equus ferus caballus) to produce fertile offspring, 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. Furthermore, mitochondrial DNA research has shown that Przewalski’s horse is not the ancestor of modern domestic horses.
Przewalski’s horse also shows a number of consistent differences in its appearance as compared to domestic horse breeds. The mane is short and erect when in good body condition and the forelocks are nearly nonexistent. The upper part of the tail has short guard hairs and a dark dorsal stripe runs from the mane down the spine to the tail. Several dark stripes can be present on the carpus and generally the tarsus, as well. Przewalski’s horses grow a thick mane in winter, which contrary to domestic horses, they shed each spring with the rest of their winter coat.
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. 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. 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. A variety of molecular studies support their phylogenetic relationship as sister taxa diverging between 150,000 and 250,000 years ago.
SUBSPECIES (3)E. f. ferus (Tarpan, Eurasian Wild Horse), E. f. caballus (Horse), E. f. przewalskii (Przewalski’s Horse)
Przewalski’s horse was named after Colonel Nikolai Mikailovich Przewalski, a famous Russian explorer who discovered the species in 1879.The first written accounts of Przewalski’s horse 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. In a Manchurian dictionary of 1771, Przewalski’s horse is mentioned as “a wild horse from the steppe.” Przewalski’s horse was not described in Linnaeus’s 1758 Systema Naturae 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. 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, the Chinese-Mongolian border.
Wild horses were reported again from what is now China by Colonel Nikolai Mikailovich Przewalski, an eminent Russian explorer, naturalist, and land surveyor, in 1897. 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 kilometers north of Gutschen (in present-day China, around 40°N, 90°E). 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, naming the species after the Colonel.
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.
Przewalski’s horse is also known as the Mongolian wild horse and the takhi – a Mongolian word meaning spirit.
ALTERNATEAsian Wild Horse, Dzungarian Horse, Mongolian Wild Horse, Takhi
GROUPHarem, Harras, Herd, Rag, Stud, String, Team
MALEGelding, Stallion, Stud
YOUNGColt, Filly, Foal
Przewalski’s horse is found in the Altai Mountains of western Mongolia. The horse once roamed throughout Europe and Asia, but today they are only found on reserves in Mongolia and China and in zoos around the world.
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. Many cave drawings in France show horses that look like Przewalski’s horse. In prehistoric times, the species probably roamed widely over the steppes of Central Asia, China, and Europe, although wild horses in Europe could have been tarpans (Equus ferus gmelini).
Until the late 18th century, Przewalski’s horse ranged from the Russian Steppes east to Kazakhstan, Mongolia and northern China. After this time, the species went into catastrophic decline. The last wild population of Przewalski’s horse survived until the mid-20th century 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.
Because the Przewalski’s horse’s historic range is not precisely known, there has been much debate about the areas in which the horses were last seen. Was it merely a refuge or was it representative of the typical/preferred habitat? The Mongolia Takhi Strategy and Plan Work Group of 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 as they had access to the rich habitats of mountain valleys and more oases than in the present time, due to these areas being occupied by herders and their livestock. Although grass and water are more available in other parts of Mongolia, these areas often have harsher winters. Subsequently, others provided evidence that the Gobi is an edge habitat, rather than an optimal habitat for Przewalski’s horses, and certainly also subject to severe winters with devastating consequences for the population.
EXTINCTKazakhstan, Russia, Ukraine
Przewalski’s horse currently inhabits grassland and desert habitats. It’s been suggested that the horse is primarily a steppe herbivore that can survive under arid conditions when there is access to waterholes.
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.
Przewalski’s horse formerly inhabited the steppe and semi-desert regions of Eurasia, but as most of this range became converted to agriculture, degraded, or was increasingly occupied by livestock, the species became restricted to semi-desert habitats with limited water resources. Lowland steppe vegetation was preferentially selected by horses at Hustai National Park and seasonal movements were affected by the availability of the most nutritious vegetation. The breadth of species consumed and dietary overlap with other ungulates increased in winter, compared to summer, although forage did not appear to be limiting. In the Gobi, the Przewalski’s horses also selected for the most productive plant communities.
Although the horse’s general elevation limit is between 1,100 and 2,000 meters, it has been reported to have lived at elevations of up to 2,438 meters, or 8,000 feet.
Przewalski’s horse is a very social animal and exhibits a harem defense polygyny. This species forms permanent herds consisting of one dominant stallion and four to ten mares with their offspring. There may be other young males in the band, but the dominant male treats them very cruelly. Traces of numerous bites have been found on two-year-old colt hides from observed herds. The stallion is responsible for the herd’s protection and coordinates daily movements of the group as they wander to graze, drink, or rest.
After sexual maturity, female Przewalski’s horses may remain with the herd but males are driven away after a year. There have been sightings of young solitary stallions, a result of the leader having driven the younger and weaker males from the herd. After dispersing from their natal band at approximately 2 years of age, male Przewalski’s horses enter bachelor groups consisting of other young males and unsuccessful older stallions. When they are five years of age or older, stallions attempt to form harems of semi-permanent membership that are held year-round. They take over already established harems, steal mares from rivals, or are joined by females dispersing from their natal harem at approximately two to three years of age.
Przewalski’s horse is not territorial. Although herds don’t mix, they will share territory because the stallions are more protective of their mares than their territory.
Home range sizes in Hustai National Park varied from 120 to 2,400 hectacres and, in addition to grazing sites, included a permanent water source, patches of forest, and ridges with rocky outcrops. In the Great Gobi B Strictly Protected Area, home ranges of 150 to 825 kilometers² were reported.
Przewalski’s horse is crepuscular and spends more than half the day foraging for food. The horse has been seen spending the day in the desert, traveling to grazing and watering areas after sun-down, and returning to the desert in the morning.
Shy and alert to avoid enemies, Przewalski’s horse has a shrill voice.
Przewalski’s horse is a herbivore, eating grass, plants, and fruit. It sometimes eats bark, leaves, and buds.
Przewalski’s horse is fed hay, grain, alfalfa, and vitamin and mineral supplements in zoos.
All perissodactyls are hindgut fermenters. In contrast to ruminants, hindgut fermenters store digested food that has left the stomach in an enlarged cecum, where the food is digested by bacteria. As an odd-toed ungulate, Przewalski’s horse digests plant cellulose in its intestines rather than in one or more stomach chambers as even-toed ungulates do. No gallbladder is present.
Very little is known about the reproductive physiology of Przewalski’s horses, but a research program at the Smithsonian Conservation Biology Institute is looking into many aspects of female and male reproductive physiology. This has become very important as many zoos in North America are reporting infertility issues and, as a result, not many foals have been born in the last ten years.
Przewalski’s horse mating and birth occurs in the same season since females come into heat seven to eight days after giving birth. Mating occurs in April or May and a single foal is born nearly a year later.
Przewalski’s horse’s gestation period is from eleven to twelve months, and it gives birth to one foal during April or May.
An hour after birth, Przewalski’s horse foals are able to stand and walk. Foals are usually born at night and by morning are able to travel with the herd. Foals begin grazing within a few weeks but continue to nurse for eight to 13 months.
Przewalski’s horses are sexually mature at about two years of age.
Przewalski’s horses exhibit a harem defense polygyny. After dispersing from their natal band at approximately 2 years of age, males enter bachelor groups consisting of other young males and unsuccessful older stallions. When they are five years of age or older, stallions attempt to form harems of semi-permanent membership that are held year-round. They take over already established harems, steal mares from rivals, or are joined by females dispersing from their natal harem at approximately two to three years of age.
BREEDING INTERVAL1 Year
ESTROUS CYCLE25.1 Days
SEXUAL MATURITY2 Years
Wolves, such as the grey wolf (Canis lupus), and humans prey on Przewalski’s horse.
There is currently no use or trade in Przewalski’s horses, though it is believed that capture of animals for cross-breeding as racehorses is a potential future use and threat.
Historically, Przewalski’s horse has declined drastically because of excessive hunting for meat by people and loss of grazing and watering areas to domestic animals. Hunting Przewalski’s horse has been prohibited since 1930, and the species is listed as Very Rare under the 1995 Mongolian Hunting Law. Hunting is not currently a threat to the species, though this needs to be monitored.
Przewalski’s horse has never been domesticated and is the only remaining species of wild horse.
After the rediscovery of 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 wild Przewalski’s horses.
It proved difficult to catch adult horses, because they were too shy and fast. Capture of foals was considered the best option as when chased they would become exhausted and lag behind their group, although this may have involved killing adult harem members in the process. That the wild horse was a prestigious gift, denoting its rarity and that it was difficult to catch, is also demonstrated by the presentation of a Przewalski’s horse to the emperor of Manchuria by Chechen-Khansoloj-Chalkaskyden, an important Mongolian, circa 1630.
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. One mare, Orlitza III, was caught as a foal in 1947 and was the last wild mare to contribute to the Przewalski’s horse gene pool in Europe. In Mongolia several Przewalski’s horses were captured and crossbred with domestic horses by the Mongolian War Ministry.
Przewalski’s horse was previously listed as Extinct in the Wild (EW) on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species from the 1960s up to the assessment in 1996. The species was then reassessed as Critically Endangered (CR) due to at least one surviving mature individual in the wild.
Successful reintroductions have qualified this species for reassessment. The population is currently estimated to consist of more than 50 mature individuals free-living in the wild for the past seven years. Przewalski’s horse now qualifies as Endangered (EN) under Criterion D.
Historically, Przewalski’s horse has declined drastically because of excessive hunting for meat by people and loss of grazing and watering areas to domestic animals.
In subsequent years the captive population increased, and since the 1990s reintroduction efforts have started in Mongolia and China. Mongolia was the first country where truly wild reintroduced populations existed within the historic range. Reintroductions in Mongolia began in the 9,000 square-kilometer Great Gobi B Strictly Protected Area in the Dzungarian Basin and the 570 square-kilometer Hustai National Park in Mongol Daguur Steppe in 1994. A third reintroduction site, Khomintal, a 2,500 square-kilometer area 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. Releases began in the 17,330 square-kilometer Kalamaili Nature Reserve, Xinjiang Province, China in 2001 and in the 6,600 square-kilometer Dunhuang Xihu National Nature Reserve, Gansu Province, China in 2010, although almost all of these animals are corralled and fed in winter. Further reintroduction sites are planned in Kazakhstan and Russia.
The Przewalski’s horse population is currently estimated to consist of more than 50 mature individuals free-living in the wild for the past seven years, now qualifying the species for Endangered (EN) assessment on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species under Criterion D.
Przewalski’s horse is threatened by small population size and restricted range, potential hybridization with domestic horses (Equus ferus caballus), loss of genetic diversity, and disease.
As the population size is small, it is also vulnerable to stochastic events such as severe weather.
There is concern over loss of genetic diversity after being reduced to a very small population and maintained in captivity for several generations. 60% of the unique genes of the studbook population have been lost. Loss of founder genes is irretrievable and further losses must be minimized through close genetic management. Furthermore, inbreeding depression could become a population-wide concern as the population inevitably becomes increasingly inbred. However, correct management of the population can slow these losses significantly, as has been achieved since the organization of the regional captive-breeding programs. Fortunately, Przewalski’s horses have been shown to have both higher nuclear and mitochondrial nucleotide diversity than many domestic horse breeds in spite of the population bottlenecks they have experienced.
AGRICULTURE & AQUACULTURELivestock Farming & Ranching
ENERGY PRODUCTION & MININGMining & Quarrying
BIOLOGICAL RESOURCE USEHunting & Trapping Terrestrial Animals
HUMAN INTRUSIONS & DISTURBANCEWar, Civil Unrest, & Military Exercises
CLIMATE CHANGE & SEVERE WEATHERDroughts, Temperature Extremes, Storms & Flooding
Przewalski’s horse is listed as Critically Endangered in both the 1987 and 1997 Mongolian Red Books, and in the Regional Red List for Mongolia. It is listed on CITES Appendix I as Equus przewalskii.
Przewalski’s horse is legally protected in Mongolia as Very Rare under part 7.1 of the 2000 Law of the Mongolian Animal Kingdom and the taxon’s re-introduced range in Mongolia is almost entirely within protected areas.
Hunting Przewalski’s horse has been prohibited since 1930, and the species is listed as Very Rare under the 1995 Mongolian Hunting Law.
- Berger, J. (1986). Wild Horses of the Great Basin. Chicago, IL & London, UK: The University of Chicago Press.
- Bokonyi, S. (1974). The Przevalsky Horse. London, UK: Souvenir Press.
- Bouman, D. T. & Bouman, J. G. (1994). The history of Przewalski’s horse In: L. Boyd & D. A. Houpt (Eds.), Przewalski’s Horse: The History and Biology of an Endangered Species (pp. 39-59). Albany, NY: State
University of New York Press.
- Bowling, A. T. & Ryder O. A. (1987). Genetic studies of blood markers in Przewalski’s horse. Journal of Heredity, 78, 75-80.
- Burton, M. (1968). University Dictionary of Mammals of the World. Ann Arbor, MI: Thomas Y. Crowell Company.
- Cai, D., Tang, Z., Han, L., Speller, C. F., Yang, D. Y., Ma, X., Cao, J., Zhu, H., & Zhou, H. (2009). Ancient DNA provides new insights into the origin of the Chinese domestic horse. Journal of Archaeological Science, 36(3), 835–842.
- Clark, E. L., Munkhbat, J., Dulamtseren, S., Baillie, J. E. M., Batsaikhan, N., Samiya, R., & Stubbe, M. (2006). Mongolian Red List of Mammals: Regional Red List Series. London, UK: Zoological Society of London.
- Côté, O., Viel, L., & Bienzle, D. (2013). Phylogenetic relationships among Perissodactyla: Secretoglobin 1A1 gene duplication and triplication in the Equidae family. Molecular Phylogenetics and Evolution, 69, 430-436.
- Denver Zoological Foundation. (1996). Przewalski’s Horse. Denver Zoo.
- Gotch, A. F. (1979). Mammals – Their Latin Names Explained. Dorset, England: Blandford Press Ltd.
- Goto, H., Ryder, O. A., Fisher, A. R., Schultz, B., Kosakovsky Pond, S. L., Nekrutenko, A., & Makova, K. D. (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.
- Groves, C. P. (1991 January 1). The taxonomy, distribution and adaptations of recent equids. In: R. H. Meadow & H. P. Uepermann (Eds.), Equids in the Ancient World (pp. 11-65). Wiesbaden, Germany: Dr Ludwig Reichert Verlag.
- Grzimek, B. (1990). Grzimek’s Encyclopedia of Mammals (Vol. 5). New York, NY: McGraw-Hill Publishing Company.
- Ishida, N., Oyunsuren, T., Mashima, S., Mukoyama, H., & 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, 41, 180-188.
- Kaczensky, P., Ganbaatar, O., Altansukh, N., Enkhsaikhan, N., Stauffer, C., & Walzer, C. (2011, December). The danger of having all your eggs in one basket – Winter crash of the Przewalski’s horses in the Mongolian Gobi. Public Library of Science ONE 6(12).
- Kaczensky, P., Ganbaatar, O., von Wehrden, H., & Walzer, C. (2008). Resource selection by sympatric wild equids in the Mongolian Gobi. Journal of Applied Ecology, 45: 1762–1769.
- Kavar, T. & Dovc, P. (2008). Domestication of the horse: Genetic relationships between domestic and wild horses. Livestock Science, 116(1–3), 1–14.
- King, S. R. B. & Gurnell, J. (2005). Habitat use andspatial dynamics of takhi introduced to Hustai National Park, Mongolia. Biological Conservation, 124: 277-290.
- King, S. R. B., Boyd, L., Zimmermann, W., & Kendall, B. E. (2015). Equus ferus (errata version published in 2016). The IUCN Red List of Threatened Species 2015: e.T41763A97204950. https://dx.doi.org/10.2305/IUCN.UK.2015-2.RLTS.T41763A45172856.en.
- Lau, A. N., Peng, L., Goto, H., Chemnick, L., Ryder, O. A., & Makova, K. D. (2009). Horse domestication and conservation genetics of Przewalski’s horse inferred from sex chromosomal and autosomal sequences. Molecular Biology and Evolution, 26(1), 199–208.
- Liu, G., Shafer, A. B. A., Zimmermann, W., Hu, D., Wang, W., Chu, H., Cao, J., & Zhao, C. (2014). Evaluating the reintroduction project of Przewalski’s horse in China using genetic and pedigree data. Biological Conservation, 171, 288-298.
- Luu, J. (2002). Equus caballus przewalskii. Animal Diversity Web.
- Mohr, E. (1971). The Asiatic Wild Horse. London, UK: J. A. Allen and Co. Ltd.
- Nowak, R. M. (1999). Walker’s Mammals of the World (6 ed., Vol. 2). Baltimore: MD: John Hopkins University Press.
- Oakenfull, E. A., Lim, H. N., & Ryder, O. A. (2000). A survey of equid mitochondrial DNA: Implications for the evolution, genetic diversity and conservation of Equus. Conservation Genetics, 1, 341-255.
- Oakenfull, E. A. & Ryder, O. A. (1998). Mitochondrial control region and 12S rRNA variation in Przewalski’s horse (Equus przewalskii). Animal Genetics, 29, 456-459.
- Ryder, O. A. (1988, July). Putting the wild horse back into the wild. Oryx, 22(3), 154-157.
- Ryder, O., Epel, N. C., & Benirschke, K. (1978). Chromosome banding studies of the Equidae.
Cytogenetics and Cell Genetics, 20, 323-350.
- Siestes, D. J., Faupin, G., de Boer, W. F., de Jong, C. B., Henkens, R. H. G., Usukhjargal, D., & Batbaatar, T. (2009). Resource partitioning between large herbivores in Hustai National Park, Mongolia. Mammalian Biology, 74, 381–393.
- Trommerhausen-Smith, A., Ryder, O., & Suzuki, Y. (1979). Bloodtyping studies of twelve Przewalski’s horses. International Zoo Yearbook, 19, 224-227.
- Steiner, C. C., Mitelberg, A., Tursi, R., & Ryder, O. A. (2012). Molecular phylogeny of extant equids and effects of ancestral polymorphism in resolving species-level phylogenies. Molecular Phylogenetics and Evolution, 65, 573-581.
- Steiner, C. C. & Ryder, O. A. (2011). Molecular phylogeny and evolution of the Perissodactyla. Zoological Journal of the Linnean Society, 163: 1289-1303.
- Van Dierendonck, M., Bandi, N., Batdorj, D., Dugerlham, S., & Munkhtsog, B. (1996). Behavioural observations of reintroduced takhi or Przewalski horses (Equus ferus przewalskii) in Mongolia. Applied Animal Behaviour Science, 50, 95-114.
- Van Dierendonck, M. & Wallis de Vries, M. F. (1996). Ungulate reintroductions: Experiences with takhi
or Przewalski horse (Equus ferus przewalskii) in Mongolia. Conservation Biology, 10, 728-740.
- Vilà, 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.
- The Wikimedia Foundation. (2021, March). Odd-Toed Ungulate. Wikipedia.