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Related subjects: Mammals

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Conservation status

Vulnerable ( IUCN 2.3)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Bovidae
Genus: Bos
Species: B. grunniens
Binomial name
Bos grunniens
Linnaeus, 1766

The yak (Bos grunniens; now Poephagus grunniens, though this new name is not universally accepted) is a long-haired bovine found throughout the Himalayan region of south Central Asia, the Qinghai- Tibetan Plateau and as far north as Mongolia. In addition to a large domestic population, there is a small, vulnerable wild yak population. In Tibetan, the word gyag refers only to the male of the species; a female is a dri or nak. In most languages which borrowed the word, including English, yak is usually used for both sexes.

Yaks are herd animals. Wild male yaks stand about 2-2.2 meters tall at the shoulder, the females about one third of that size, and domesticated yaks about 1.6-1.8 meters. Both types have long shaggy hair to insulate them from the cold. Wild yaks can be brown or black. Domesticated ones can also be white. Both males and females have horns.

Domestic yaks mate in about September; the females may first conceive at about 3-4 years of age, calving April to June about every other or every third year, apparently depending upon food supply. This gestation period is approximately 9 months. In the absence of more data, wild animals are assumed to mirror this reproductive behaviour. Calves will be weaned at one year and become independent shortly thereafter. Yaks may live to somewhat more than 20 years.

Wild yaks

Yak at the Saskatoon Zoo

Wild yaks (Tibetan: drong) can weigh up to 1,200 kg (2,400 lb) and have a head and body length of 3-3.4 meters. They usually form groups of between 10 and 30 animals. Their habitat is treeless uplands like hills, mountains and plateaus between 3,200 m (10,500 ft) and roughly 5,400 m (18,000 ft). Yaks physiology is well adapted to high altitudes, having larger lungs and heart than cattle found at lower altitudes, as well as greater capacity for transporting oxygen though their blood . Conversely, yaks do not thrive at lower altitudes . They eat grasses, lichens and other plants. They are insulated by dense, close, matted under-hair as well as their shaggy outer hair. Yaks secrete a special sticky substance in their sweat which helps keep their under-hair matted and acts as extra insulation. This secretion is used in traditional Nepalese medicine. Many wild yaks are killed for food by the Tibetans; they are now a vulnerable species.

Thubten Jigme Norbu, the elder brother of Tenzin Gyatso, the 14th Dalai Lama, reports on his journey from Kumbum in Amdo to Lhasa in 1950 that:

"Before long I was to see the vast herds of drongs with my own eyes. The sight of those beautiful and powerful beasts who from time immemorial have made their home on Tibet's high and barren plateaux never ceased to fascinate me. Somehow these shy creatures manage to sustain themselves on the stunted grass roots which is all that nature provides in those parts. And what a wonderful sight it is to see a great herd of them plunging head down in a wild gallop across the steppes. The earth shakes under their heels and a vast cloud of dust marks their passage. At nights they will protect themselves from the cold by huddling up together, with the calves in the centre. They will stand like this in a snow-storm, pressed so close together that the condensation from their breath rises into the air like a column of steam. The nomad have occasionally tried to bring up young drongs as domestic animals, but they have never entirely succeeded. Somehow once they live together with human beings they seem to lose their astonishing strength and powers of endurance; and they are no use at all as pack animals, because their backs immediately get sore. Their immemorial relationship with humans has therefore remained that of game and hunter, for their flesh is very tasty."

Domesticated yaks

A Tibetan yak.

Domesticated yaks are kept primarily for their milk, fibre and meat, and as beasts of burden. They transport goods across mountain passes for local farmers and traders as well as for climbing and trekking expeditions. They also are used to draw ploughs. Yak dung is even burned as fuel. Yak milk is often processed to a cheese called chhurpi in Tibetan and Nepali languages, and byaslag in Mongolia. Butter made of Yaks' milk is an ingredient of the butter tea that Tibetans consume in large quantities, and is also used in lamps and made into butter sculptures used in religious festivities.

Often the pack animals are actually crossbreeds of the yak and Bos taurus (common domestic cattle). These are known in Tibetan as dzo or dzopkyo, and in Mongolian as khainag. Yaks grunt, and unlike cattle are not known to produce the characteristic bovine lowing sound.

Yak fibers are soft and smooth and come in several colors, including shades of gray, brown, black and white. They are about 1.2 inches long and are combed or shed from the yak and then dehaired. The result is a downy fibre that can be spun into yarn for knitting. The animals' hair is turned into ropes, rugs and various other products. Their hide is used to make shoes and bags and in the construction of coracle-like boats.

In sport

In parts of Tibet, yak racing is considered a high source of entertainment at traditional Tibetan festivals.

More recently, sports involving domesticated yaks, such as yak skiing, or yak polo, are being marketed as tourist attractions in Central Asian countries.

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