Overview

Brief Summary

Biology

Well adapted for life in cold and harsh conditions, the wild yak is protected from the cold by its thick coat and low number of sweat glands, which help to conserve body heat. It has a large lung capacity and particularly small and numerous red blood cells, enabling it to get the most oxygen possible from the thin, mountain air. Considering its bulk, the wild yak is fairly nimble as it moves around on snowy rocks, grazing on grasses, herbs and lichens, and eating ice and snow as a source of water. It feeds mostly in the morning and evening, and will travel long distances due to the scarcity of the vegetation. With so much protection against cold weather, the wild yak is very sensitive to heat and moves seasonally to avoid higher temperatures. It can withstand strong winds and snowstorms for hours, but may bathe in lakes and streams when the temperature is exceptionally low (4). Wild yaks tend to gather together, especially the females and young, forming herds of usually 10 to 30 animals, but herds up to 200 are also found. Herds have no fixed members and may join together, or split into smaller herds. Females reach sexual maturity at three to four years, although full size is not reached until six to eight years. Mating takes place in September and single calves are born from April to June, after a gestation of 260 days. The young are weaned before they are one year old, but females will not give birth again for another year. Wild yaks can live for up to 23 years (4).
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Description

A huge and imposing hulk of an animal, the wild yak has stocky, high and humped shoulders and a broad, drooping head. Both males and females have horns, which grow out of the sides of the head and curve upwards halfway along their length. The horns of females are shorter than those of the males, reaching just 51 centimetres, compared to 95 centimetres in males; females are also just one third of the body size of males (2). For protection against the extreme cold of Tibet, the wild yak has a dense undercoat of soft, closely-matted fur, covered by dark brown, long and shaggy hair that almost reaches the ground (4). The legs are relatively short and have broad hooves that are slightly splayed to aid walking through thick snow (2).
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Distribution

Range Description

Historically, this species occurred throughout the Tibetan Plateau, including China (Gansu, Sichuan, Xinjiang, Tibet, Qinghai), northern India (Ladak), and Nepal (Schaller and Liu, 1996). According to Smith and Xie (2008), the species apparently occurred in Kazakhstan, Mongolia and southern Russia until the 13th-18th centuries, although these countries are not included on the IUCN Red List country list or range map, given the uncertainty surrounding the dates of extinction, and whether they occurred in these places after the year 1500, the cutoff date for recording extinctions on the IUCN Red List.

The species is considered extinct in both Nepal and Bhutan. Until recent decades wild yak penetrated northern Nepal (Miller et al. 1994), but there is no evidence that the species still occurs in Nepal and is considered extinct in the country. In India, the species is currently known from Ladakh region of Kashmir (Schaller and Liu 1996, Ul-Haq 2003).

In China, the species occurs in scattered populations on the Tibetan Plateau (Gansu, Qinghai, Xinjiang, Tibet), with the main populations remaining in the Chang Tang Reserve, covering 284,000 km² between in northern Tibet (Schaller and Liu, 1996, Fox et al. 2004), as well as in the Arjin Shan area of southeastern Xinjiang, and Kekexili Nature Reserve in Qinghai and adjacent areas of the Kunlun Mountains (Harris et al. 1999; Harris and Loggers 2004, Schaller et al., 2007). There are also isolated populations north and south of the main population, in the west central Tibet, south-central Qinghai, and western Gansu.

Grubb (2005) mentions the existence of feral populations in a few places within China, but these do not appear to have conservation significance.
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Historic Range:
China (Tibet), India

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Range

The wild yak was once numerous and widespread on the entire Tibetan plateau to the north of the Himalayas, but it is now found only in remote areas of this region, where there is little human disturbance. A few wild yaks have been seen in the Chang Chemmo Valley of Ladakh in eastern Kashmir, India. The wild yak is thought to number 10,000 to 15,000, and is distinct from the smaller domestic yak, whose population numbers 12,000,000 (4).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Wild yaks live in the alpine tundra, grasslands, and cold desert regions of the northern Tibetan plateau (Wiener et al. 2003). These mountainous areas range from 4,000 to 6,100 m elevation. In the Chang Tang Reserve in northwestern Tibet, the average annual precipitation is only 100–300 mm, much of it falling as hail and snow; lakes are generally saline and surface water is scarce. Temperatures can fall below -40°C. Vegetation is sparse, and is dominated by grasses, sedges, forbs, and low or procumbent shrubs; much of it can be classed as alpine, or high cold steppe (Schaller and Gu 1994). The species moves seasonally, descending into lower valleys in the winter (Miller et al. 1994, Smith and Xie 2008). It feeds mostly on grasses and sedges, with some forbs. Yaks are gregarious, often aggregating into groups of > 100 individuals, although smaller groups of 10-20 are also common. Adult males often travel with females and young, although older males will often form small groups of 2-5, and travel separately from maternal herds.

Systems
  • Terrestrial
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Found in alpine tundra and cold desert regions in uninhabited mountainous regions between 4,000 and 6,000 metres above sea level. These regions are subject to temperatures dropping below -40ºC, much hail and snow, saline lakes and sparse vegetation (1). The wild yak spends the colder months of the year at lower elevations, but retreats into higher regions during the warmer period between August and September each year (4).
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
A2ac+3c+4c

Version
3.1

Year Assessed
2008

Assessor/s
Harris, R.B. & Leslie, D.

Reviewer/s
Burton, J. & Hedges, S. (Asian Wild Cattle Red List Authority)

Contributor/s

Justification
The species is listed as Vulnerable under criterion A2ac, because it is inferred that it has declined over 30% over the last 30 years (generation length estimated at 10 years), based on direct observations, the decline in range, and continued threats to its habitat, particularly in the eastern portion of its remaining range. Similar reductions are projected into the future (criteria A3c+4c). The total number of mature individuals may be close to 10,000 because the total population was estimated to be around 15,000 in 1995.

History
  • 2000
    Vulnerable
  • 1996
    Vulnerable
  • 1994
    Endangered
    (Groombridge 1994)
  • 1990
    Endangered
    (IUCN 1990)
  • 1988
    Endangered
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Endangered
    (IUCN Conservation Monitoring Centre 1986)
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Current Listing Status Summary

Status: Endangered
Date Listed: 06/02/1970
Lead Region: Foreign (Region 10) 
Where Listed: Entire


Population detail:

Population location: Entire
Listing status: E

For most current information and documents related to the conservation status and management of Bos mutus, see its USFWS Species Profile

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Status

The wild yak is classified as Vulnerable (VU) on the IUCN Red List (1) and is listed on Appendix I of the Convention on Migratory Species (CMS or Bonn Convention) (3). It is also listed under Schedule I of the Indian Wildlife Protection Act 1972 (1).
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Population

Population
Schaller and Liu (1996) estimated 8,000–8,500 wild yaks in Tibet, of which about 7,000–7,500 were in the Chang Tang Reserve (284,000 km²), plus about 3,200–3,700 in Qinghai Province, and about 2,000–2,500 in Xinjiang. These figures were, of necessity, a combination of estimates and inferences, but they suggest that the world population of wild yak was probably about 15,000 in 1995 (Miller et al. 1994, Schaller 1998). The population trend is downward in many areas: wild yak in the southern 24% of Chang Tang have been almost exterminated with the arrival of pastoralists since the 1960s. The Arjin Shan Reserve (Xinjiang Uygur) had a substantial subpopulation in the late-1980s, but the subpopulation declined precipitously in the early-1990s (Achuff and Petocz 1988; Schaller and Liu 1996). However, at least one area in Qinghai, locally termed “Wild Yak Valley”, has retained a high abundance of wild yaks (approximately 1,700 counted in 2002), with no evidence of decline (and possibly an increase) from the early 1990s through at least 2007 (Harris et al. 1999; Harris and Loggers 2004; Harris 2007; Harris, unpublished data, 2007). Schaller et al. (2007) tallied 977 wild yaks during a winter-time transect through the northern Chang Tang and Kekexili Nature Reserves into the western-most part of the Sanjiangyuan Nature Reserve.

In India, only a very few Wild Yak remain, with some individuals moving seasonally into the Ladakh region of Kashmir from areas controlled by China (Schaller and Liu 1996; Ul-Haq 2003).

Population Trend
Decreasing
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Threats

Major Threats
Poaching, including commercial poaching for meat, has been seen as the most serious threat to wild yaks (Schaller and Gu 1994; Miller and Schaller 1997; Harris et al. 1999). Males tend to be more vulnerable to hunting, especially by motorized hunters, because they tend to disperse away from the hill bases and high ridges apparently preferred by females (Schaller and Gu 1994). However, with the confiscation of weapons in most of the Qinghai-Tibet Plateau, poaching has declined as a threat to yak populations. However, wild yaks have limited tolerance for disturbance from people and their livestock; they tend to move away from areas where livestock are herded. Increasing livestock herds and increased intensity of pasture use displaces wild yaks and ultimately reduces availability of wild yak habitat (Harris 2007).

Interbreeding between domestic and wild yaks also presents a threat to the remaining Wild Yak populations (NRC 1983; Khan 1984; Schaller and Liu 1996; Harris et al. 1999; Smith and Xie 2008). Diseases transmitted from domestic livestock, either directly or via other wild species, may be an additional threat, although this has not yet been documented. Schaller and Gu (1994) documented low recruitment in a wild yak population in the Chang Tang Reserve in 1990. Only 6.7% of the total population sample (n=586) in the Aru basin of Chang Tang Reserve were young of that year; in the nearby Yalung basin the figure was only 5.3% (n=114). Even fewer young were recorded in 1992: only 1.0% of the population (n=315) comprised young animals and only one yearling was seen (n=225) in the Aru basin. It is unknown whether this reproductive failure was due to disease - e.g., brucellosis, which can cause spontaneous abortion - or to high levels of postpartum mortality (Schaller and Gu 1994).

Where wild yaks have held on or increased in numbers, interactions and conflicts with domestic pastoralists have recently increased (including abducting domestic yaks into wild herds, and in some cases, damage to humans or their property; Tsering et al. 2006). This has the potential to increase retaliatory killing (although it presently appears to be rare).

If domestic livestock can be kept out of the large nature reserves containing wild yaks, their persistence is likely. However, the geographic range of wild yaks has evidently continued to contract toward the west, with herds east of the Golmud-Lhasa highway increasingly small and isolated (Schaller et al. 2007).
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Wild yaks are hunted commercially for their meat. Also, habitat loss brought about by pastoralists has reduced their range by more than half in the last hundred years. Interbreeding between domestic yaks and wild yaks, as well as the transmission of diseases from domestic livestock to wild yaks has also contributed to a decline in population numbers (1).
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Management

Conservation Actions

Conservation Actions
This species is listed on CITES Appendix I. Wild Yak have been protected in China since 1962, and are currently listed as a Class I protected animal, which means that they are totally protected by the central government. Within China, wild yaks exist in a number of large nature reserves, including the Arjin Shan, Chang Tang, Kekexili, Sanjiangyuan, and Yanchiwan Nature Reserves, although none of these reserves provide complete protection from habitat loss or occasional poaching.

In India, the species receives total protection under The Wildlife (Protection) Act 1972 (IUCN-ELC in litt. to Hedges 1991).
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Conservation

The wild yak has been protected in China since 1962 as a Class I protected animal, but this is almost completely without enforcement in the remote areas inhabited by yaks, and commercial hunting continues. Only the very large Chang Tang Reserve in China provides real protection for the remaining wild yak. Whilst the population is less significant in India, the wild yak is also protected there under the Wildlife Protection Act of 1972 (1).
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