The yak (Bos grunniens) 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 behavior. Calves will be weaned at one year and become independent shortly thereafter. Yaks may live to somewhat more than 20 years.
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.
Domesticated yaks are kept primarily for their milk, fiber 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 fiber 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.
Yaks link Tibetans to their homeland; A Cold Spring farmer finds that his herd has reconnected a bond between the exotic animals and the Asian people.(NEWS)
Sep 30, 2000; On a recent brilliant autumn day, a farmer led his herd of Tibetan yaks up a slope and across the wind-blown green land....