Wild yak

The wild yak (''Bos mutus'') is a large, wild bovine native to the Himalayas. It is the ancestor of the domestic yak (''Bos grunniens'').

Taxonomy

The ancestor of the wild and domestic yak is thought to have diverged from '' Bos primigenius'' at a point between one and five million years ago. The wild yak is now normally treated as a separate species from the domestic yak (''Bos grunniens'').

Description

The wild yak is among the largest extant bovid species. Adults stand about tall at the shoulder, and weigh . The head and body length is , not counting the tail of .Han Jianlin, M. Melletti, J. Burton, 2014, Wild yak (Bos mutus Przewalski, 1883), Ecology, Evolution and Behavior of Wild Cattle: Implications for Conservation, Chapter 1, p.203, Cambridge University Press The females are about one-third the weight and are about 30% smaller in their linear dimensions when compared to bull wild yaks. Domesticated yaks are somewhat smaller.

They are heavily built animals with a bulky frame, sturdy legs, and rounded cloven hooves. To protect against the cold, the udder in females and the scrotum in males are small, and covered in a layer of hair. Females have four teats. Both sexes have long shaggy hair, with a dense woolly undercoat over the chest, flanks, and thighs for insulation against the cold. In males especially, this undercoat may form a long "skirt" that can reach the ground. The tail is long and horse-like, rather than tufted like the tails of cattle or bison. The coat is typically black or dark brown, covering most of the body, with a grey muzzle (although some wild golden-brown individuals have been reported). Wild yaks with gold coloured hair are known as the wild golden yak (). They are considered an endangered subspecies in China, with an estimated population of 170 left in the wild.

Two morphological types have been identified, so-called ''Qilian'' and ''Kunlun''.

Distribution and habitat

Wild yaks once ranged up to southern Siberia to the east of Lake Baikal, but became extinct in Russia around the 17th century. Today, wild yaks are found primarily in northern Tibet and western Qinghai, with some populations extending into the southernmost parts of Xinjiang, and into Ladakh in India. Small, isolated populations of wild yak are also found farther afield, primarily in western Tibet and eastern Qinghai. In historic times, wild yaks were also found in Bhutan, but they are now considered extinct there.

The primary habitat of wild yaks consists of treeless uplands between , dominated by mountains and plateaus. They are most commonly found in alpine tundra with a relatively thick carpet of grasses and sedges rather than the more barren steppe country.

The wild yak was thought to be regionally extinct in Nepal in the 1970s, but was rediscovered in Humla in 2014. This discovery later made the species to be painted on Nepal's currency.

Behaviour and ecology

The diet of wild yaks consists largely of grasses and sedges, such as '' Carex'', '' Stipa'', and '' Kobresia''. They also eat a smaller amount of herbs, winterfat shrubs, and mosses, and have even been reported to eat lichen

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