Originally these massive animals were found throughout their range, but centuries of hunting and persecution have forced them to retreat into remote and inaccessible areas of mountain tundra and ice desert, and now they cannot live in warm, lowland areas.
The wild yak is now scarce - the surviving population numbers no more than 15,000 individuals, in contrast to around 14 million domestic yaks.
Yaks are closely related to cattle, and have been domesticated since around 1000 BC. There are nearly 13 million domestic yaks around the high plateaux of Central Asia, where they are used as draught animals and for milk, meat and wool production.
Today this species is very important in the economies of the areas where its occurs. Domestic yaks are smaller in size, and more variable in colouration than their wild relatives. Few animals are as hardy, and yaks can be found in areas where the temperature drops far below freezing in winter. Indeed, they are uncomfortable in hot weather.
Yaks are well suited to cold, high-altitude conditions, being powerful but docile. There are probably only a few thousand wild yaks, ranging from eastern Kashmir along the Tibetan-Chinese border into the Qinghai province of China.
Yaks have stocky bodies and very long black-brown woolly fur that almost reaches to the ground, to help keep them warm. Wild yaks are larger and have stronger horns than domestic yaks.
Yaks spend the short summers feeding in sparse alpine meadows, and in winter they descend into the valleys. Females usually live together in large herds that used to be thousands strong when wild yaks were more abundant. Males live alone or in small groups of less than 12 animals until the breeding season, when they join the herds to fight over females. Yaks mate in September, when the bulls will fight over the cows.
Although wild yaks are an endangered species, they have been domesticated for centuries in Tibet, where, as well as being used as pack animals and to pull carts, they also provide milk, meat, hides and hair and wool, which the local population weave into warm cloth. Domestic yaks are often without horns. The coat of the domestic yak is redder than that of the wild yak, mottled with brown, black and sometimes white.
Distribution: Typically occurs at altitudes of 4000—6000m (12,800-19,200ft) in Tibet. Also present in China, India and possibly Nepal if it is not extinct there.
Habitat: Highland and mountainous steppes to 20,000 ft (6,100 m).
Weight: 305 - 820 kg (670 - 1805 lb).
Length: Up to 385 cm (152 in), including tail; can measure 200 cm (78 in) tall at the shoulder.
Maturity: 6-8 years.
Gestation Period: About 258 days; calves weaned by about 1 year old.
Breeding: 1 calf every second year.
Food: Herbivorous, grazing on grass as well as other plants and tubers.
Lifespan: Up to 23 years.
Horns curve upwards, growing to 95 cm (38 in) in males, shorter in females.
Head and shoulders
The head is relatively low-set, and the shoulders have a distinctive humped appearance.
The coat is blackish-brown, although very rare golden-coated individuals are known.
Legs and feet
Yaks have short legs and large hooves, with dew claws to prevent them from slipping.
BATTLING ON THE PLATEAU
Two bulls clash during the breeding season. This is also the time of year when they emit their distinctive grunting calls.