YAK

(species Bos grunniens), large, massively built ox, family Bovidae (order Artiodactyla), of the Tibetan plateaus 4,3006,100 m (14,00020,000 feet) above sea level. Some large yak bulls attain heights of about 1.8 m (6 feet) at the shoulder hump; cows and domesticated varieties are much smaller. The hair of wild yak is black and short, except on the flanks and tail where it forms a long, shaggy fringe. The horns spread outward and upward, and the head is held low like that of the bison. Wild yaks (Bos grunniens mutus) live in large herds of females, young bulls, and calves, the mature bulls staying together in smaller groups. Mating takes place in winter, and the calves are born in the following autumn. Yaks graze on grass and require much water (they are said to eat snow in winter). Wild yaks, now reduced in numbers and considered endangered, are found mainly in northern Tibet. Domestic yaks, which breed freely with domestic cattle, are often piebald black and white; they are used as pack, draft, and saddle animals in the plateaus and mountains. The hides of both wild and tame yaks provide leather, and the tails are valued as fly whisks in India. Domesticated yaks are also kept for milk and beef. The hair from the long fringes of the flanks is used in making cords and ropes. The dried dung of the yak is the only obtainable fuel on the treeless Tibetan plateaus.