Scientific Name: Bos grunniens
Description: Yaks are stocky, ox-like animals with a broad head and large humped shoulders. They have thick, wooly fur. The guard hairs are short on the back and much longer along the sides, forming a fringed cape that reaches almost to the ground. Their tail is long and bushy, also with long guard hairs. Both sexes have horns. Wild yaks can stand 6 ½ feet tall at the shoulders and weigh up to 2,200 pounds. Females are much smaller, reaching only a third of the males’ weight. Domestic yaks are smaller than the wild form, and have weaker horns. While wild yaks are always blackish brown, domestic yaks can have reddish, brown, black, or mottled coloring.
Home Range: Wild yaks are found only in a mountain chain extending from the northern tip of India, along the border of Tibet, and into the Chinese province of Qinghai. Domestic yaks can be found throughout the Himalayas in association with people.
Habitat Type: High-elevation plateaus and mountain slopes with sparse vegetation. Yaks spend the warmest months at elevations up to 20,000 feet, migrating to lower elevations for the rest of the year.
Reproduction: Wild yaks begin breeding in September. Mature males join the females’ herds for approximately four weeks. During this time, males fight over females by pushing against each other, forehead to forehead, or trying to gore each others’ flanks with their horns. Fighting between males often looks fierce, but rarely results in injury. After breeding, gestation lasts nine months. Most calves are born in June. In the wild, females have a single calf every other year. Domestic yaks have less predictable reproductive cycles, with some females giving birth every year. Calves are independent by one year of age, and reach full size at 6-8 years.
Diet in the Wild: Grass, herbs, shrubs, and lichens.
Diet in the Zoo: Prairie hay, alfalfa, LRZ grain (custom herbivore diet)
General Information: Wild yaks might have been domesticated more than 4,000 years ago. At the latest, they were in use during the first millennium B.C., when they were recorded on murals in Buddhist monasteries in Tibet. Their horns still figure in Buddhist rituals, and the yaks themselves are still in wide use on the high plateaus and mountains of the Himalayas. At such high elevations, yaks are the most useful domestic animal. They are strong but docile. They are used in travel and as draft animals, and are also valued for their milk, meat, wool, and dung (which is used as fuel). They require very little food, and like their wild relatives, they can withstand temperatures as low as -40oF. During blizzards, yak herds can lay motionless for days, facing away from the wind. They are expert climbers, traveling easily among steep cliffs and rocky terrain.
In the past, wild yaks traveled in large herds of thousands of females and calves. Female herds now number 6-20 individuals. Occasionally larger herds of more than 100 are spotted. When threatened by a predator, herds bunch together to face the predator, keeping the calves in the center of the group. Adult males spend most of the year alone, or in small groups.
Domestic yaks can reproduce with other varieties of domestic cattle. In particular, yak-zebu hybrids are becoming common. Domestic yaks produce a strange grunting sound, earning the nickname “grunting ox”. Wild yaks can produce the sound too, but only do so during the short breeding season.
Conservation Status: Wild yaks are listed as endangered by USFWS, and are listed on CITES Appendix 1. The remoteness of their habitat makes it difficult to estimate their population size – current estimates range from a few hundred individuals to thousands. The remoteness of their habitat makes research difficult. Habitat loss and uncontrolled hunting are the main problems for this species. As humans bring domestic yaks or other livestock to graze on high-altitude pastures, wild yaks are forced up the mountain slopes to marginal habitat. Plant productivity is low at such high elevations, so any competition with domestic livestock can cause severe problems for wild yaks. Interbreeding between domestic and wild yaks may pose additional threats to wild populations. Wild yaks are officially protected in China, but hunting for meat and hides continues. Domestic yaks are common.
Predators: Snow leopards.
Grzimek’s Animal Life Encyclopedia, Ed. 2 Vol. 16. 2003. M. Hutchins. Gale Group, Farmington Hills, MI. p. 18.
The Story of Domestication: Wild Ancestors and Relatives of Domestic Animals. 1991. D.F. Hardy and E. McIntire. California State University, Northridge. pp. 51-52.
Walkers Mammals of the World, Vol. 2. 1999. R.M. Nowak. Johns Hopkins University Press, Baltimore. pp. 1160-1161.