|Scientific Name:||Bos mutus|
|Species Authority:||(Przewalski, 1883)|
|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.
|Red List Category & Criteria:||Vulnerable A2ac+3c+4c ver 3.1|
|Assessor/s:||Harris, R.B. & Leslie, D.|
|Reviewer/s:||Burton, J. & Hedges, S. (Asian Wild Cattle Red List Authority)|
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.
|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.
Regionally extinct:Bhutan; Nepal
|Range Map:||Click here to open the map viewer and explore range.|
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).
|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.|
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).
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:||Harris, R.B. & Leslie, D. 2008. Bos mutus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 10 December 2013.|