Wild yak (Bos mutus)
|Also known as:||yak|
|Synonyms:||Bos grunniens, Bos mutus grunniens|
|Size||Head-body length: up to 325 cm (2)|
Shoulder height: up to 200 cm (2)
Tail length: 60 cm (2)
|Weight||305 – 820 kg (2)|
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).
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).
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).
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).
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).
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).
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).
For further information on the wild yak see:
- Ultimate Ungulate:
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- Gestation: the state of being pregnant; the period from conception to birth.
- Interbreeding: cross-breeding with a different species or subspecies.
- Pastoralist: a social and economic system based on the raising and herding of livestock.
- Tundra: treeless, grassy plains characteristic of arctic and sub-arctic regions. They are very cold and have little rainfall.
IUCN Red List (January, 2009)
Ultimate Ungulate (February, 2005)
Convention on Migratory Species (February, 2005)
Animal Info (February, 2005)