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Bos mutus 

Scope: Global
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Bovidae

Scientific Name: Bos mutus
Species Authority: (Przewalski, 1883)
Common Name(s):
English Wild Yak, Yak
Taxonomic Notes: The International Commission on Zoological Nomenclature (2003) ruled that the name for this wild species is not invalid by virtue of being antedated by the name based on the domestic form. Therefore, IUCN considers the wild species of yak under Bos mutus, while the domestic form is considered under Bos grunniens (see Gentry et al. 1996).

Grubb (2005) lists mutus as a subspecies of grunniens, contrary to most authors.

Assessment Information [top]

Red List Category & Criteria: Vulnerable C1 ver 3.1
Year Published: 2016
Date Assessed: 2014-07-09
Assessor(s): Buzzard, P. & Berger, J.
Reviewer(s): Burton, J.
Contributor(s): Harris, R., Leslie, D.M. Jr. & Sankar, K.
Justification:

The species is listed as Vulnerable under criterion C1. It is estimated that the population of mature individuals is less than 10,000, and it is estimated that there will be a continuing decline of at least 10% in 30 years (generation length estimated at 10 years) from poaching and continued threats to its habitat, particularly in the eastern portion of its remaining range. In most areas there is also a danger of Wild Yak hybridizing with domestic yak (Bos grunniens). This is a particular concern because there is a long history of domestic cattle (Bos taurus) admixture with domestic Yak populations (Qi et al. 2009). Similar reductions are projected into the future.

Previously published Red List assessments:

Geographic Range [top]

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 cut-off 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). Recent reports of Wild Yak in northwest Nepal (R. Acharya pers. comm.)  need to be confirmed. In India, the species is currently known from Ladakh region of Jammu & Kashmir (Rawat and Sankar 2011).

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 199, 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 east 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.
Countries occurrence:
Native:
China; India
Regionally extinct:
Bhutan
Additional data:
Lower elevation limit (metres):4000
Upper elevation limit (metres):6100
Range Map:Click here to open the map viewer and explore range.

Population [top]

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). However, the population trend has been downward in many areas: Wild Yak in the southern 24% of Chang Tang have been almost exterminated with the arrival of herders since the 1960s. In the last IUCN Red List assessment, Harris and Leslie (2008) estimated the population for Wild Yak at no more than 10,000 mature individuals, and this is still likely.

Recent protection from poaching has allowed populations to remain stable or increase in some areas but available habitat for expansion is limited because of competition with domestic livestock (Harris 2007). The Arjin Shan Reserve in Xinjiang had a substantial sub-population in the late-1980s, but the subpopulation declined precipitously in the early 1990s (Achuff and Petocz 1988, Schaller and Liu 1996). Buzzard et al. (2010) noted that the subpopulation seems to be stable or increasing. They recorded a minimum of 1,700 Yaks in the northeast of Arjin Shan and estimate that at least 2,000-2,500 Wild Yak remain in Arjin Shan. In addition, 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 unpub. data 2007). Schaller et al. (2007) tallied 977 Wild Yaks in November 2006 through the northern Chang Tang and Kekexili Nature Reserves into the western-most part of the Sanjiangyuan Nature Reserve. Schaller et al. (2007) observed the majority of Yaks (713) in Kekexili, and this is an increase from the 502 Yaks observed along the same route in November 2004 (Buzzard 2004 referenced in Schaller et al. 2007). Schaller (2012) also noted an increase over time in the number of Wild Yaks seen in the eastern Chang Tang.

In India, a maximum of around 110 Wild Yak remain, with some individuals moving seasonally into the Ladakh region of Jammu and Kashmir from areas controlled by China (Schaller and Liu 1996, Ul-Haq 2003, Rawat and Sankar 2011). This population has likely increased from the very few Yak previously reported (Schaller and Liu 1996, Ul-Haq 2003), but threats remain from competition with domestic livestock and interbreeding with domestic Yak (Rawat and Sankar 2011).
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:7500-9999Continuing decline of mature individuals:Yes
Population severely fragmented:No

Habitat and Ecology [top]

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 travel alone or form small groups of 2-5. Male herds range mostly at lower altitudes and in less rugged topography than females (Berger et al. 2014).
Systems:Terrestrial
Generation Length (years):10

Use and Trade [top]

Use and Trade:

As Chinese become wealthier and more join the middle class meat consumption has increased (Zhou et al. 2012). As a result the consumption of domestic Yak is increasing. 

Threats [top]

Major Threat(s): 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, Berger et al. 2014). 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, Rawat and Sankar 2011). 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). In some villages of Sanjiangyuan reserve, Qinghai, however, Wild Yaks are protected for the hybridization benefits of Wild Yak bulls breeding with domestic Yak cows even though domestic cows are occasionally lost to wild herds and a domestic bull was killed (Buzzard 2011).  Future research into management techniques will hopefully reduce or eliminate the loss of domestic Yak to wild herds, and buffer zones without domestic Yak are being investigated in the Chang Tang Reserve.

Conservation Actions [top]

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).

Citation: Buzzard, P. & Berger, J. 2016. Bos mutus. The IUCN Red List of Threatened Species 2016: e.T2892A101293528. . Downloaded on 04 December 2016.
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