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Scientific Classification

Conservation Status

Vulnerable!

Kingdom:

Animalia

Phylum:

Chordata

Class:

Mammalia

Order:

Artiodactyla

Family:

Bovidae

Genus:

Bos

Species:

B. grunniens

Binomial name:

Bos grunniens, Linnaeus, 1766

Subspecies:

Bos grunniens grunniens, Bos grunniens mutus

Description

The yak (Bos grunniens) is a long-haired humped domestic bovine found in Tibet and throughout the Himalayan region of south central Asia, as well as in Mongolia. In Tibetan, the word yak refers only to the male of the species; a female is a dri or nak. In most languages which borrowed the word, including English, however, yak is usually used for both sexes.

Wild yaks stand about two meters tall at the shoulder. Domestic yaks are about half that height. Both types have long shaggy hair to insulate them from the cold. Wild yaks can be either brown or black. Domesticated ones can also be white. Both males and females have horns.

Wild Yaks

Wild yaks can weigh 1,000 kg (2,200 lb). They usually form groups of between 10 and 30 animals. Their habitat is treeless uplands like hills, mountains and plateau between 3,200 m (10,500 ft) and roughly 5,400 m (18,000 ft). They eat grasses, lichens and other plants. They are insulated by dense, close, matted under-hair as well as their shaggy outer hair. Many wild yaks are killed for food by the Tibetans; they are now an endangered species.

The wild yak was once numerous and widespread on the entire Tibetan plateau north of the Himalayas. Currently it is found in remote areas of the Tibetan plateau and adjacent highlands, including Gansu Province, China, with a few having been observed in the Chang Chenmo Valley of Ladakh (eastern Kashmir, India). Wild yak distribution is highly clumped, with most animals in widely scattered herds, concentrated in the areas with little disturbance by humans. A survey conducted in 2003 found increasing populations of wild yak compared to previous surveys taken 10 years earlier.

Uncontrolled hunting by natives and military personnel is the main reason for the wild yak's decline. Its range has been reduced by more than half during this century. Poaching remains the main current threat. The wild yak has lost most of the best alpine meadow and steppe habitat to pastoralists. Problems are also caused by habitat disturbance, hybridization and competition with domestic yaks, and disease transmitted by domestic yaks.

Domesticated Yaks

Domesticated yaks are kept primarily for their milk, fiber, and meat; they are also used as beasts of burden, transporting goods across mountain passes for local farmers and traders as well as in support of climbing and trekking expeditions, their dung is even burned to produce energy. Yak milk is often processed to a cheese called chhurpi in Tibetan and Nepali languages, and byaslag in Mongolia. 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. Unlike cattle, yaks grunt rather than moo.

Yak fibers are soft and smooth, in several colors, including shades of gray, brown, black and white. The length of yak fiber is about 1.2 inches. It is combed or shed from the yak and then dehaired. The result is a splendid downy fiber that can be spun into yarn for knitting.

More recently, sports involving domesticated yaks, such as yak skiing, [Nat-han ] [ Tede-schi] or yak polo, are being marketed as tourist attractions in Central Asian countries.

Yak Statistics (from www.animalinfo.org/species/artiperi/bos_mutu.htm)

Size and Weight:

The male wild yak can weigh up to 1000 kg (2200 lb); females are 1/3 that size. Its shoulder height can reach over 2 m (6.5').

Habitat:

The wild yak occurs (or has occurred) in treeless uplands, including plains, hills, and mountains, from as low as 3200 m (10,500') up to the limit of vegetation at about 5400 m (18,000'). It reached its greatest abundance on alpine meadows. On alpine steppe, herds were also large on occasion but were more widely dispersed, and in desert steppe they were scarce. (Schaller 1998) The wild yak is one of the species that live in both the Mountains of Southwest China Biodiversity Hotspot (Cons. Intl. 2005) and the Tibetan Plateau Steppe Global 200 Ecoregion. (Olson & Dinerstein 1998, Olson & Dinerstein 1999)

Age to Maturity:

In domestic yaks, females first conceive at the age of 3 - 4 years. Full size is reached at 6 - 8 years.

Gestation Period:

Approximately 260 days (Bhatnagar 2002).

Birth Season:

Most births would be expected to occur from April through June (Schaller 1998). Mating occurs in September (Bhatnagar 2002).

Birth Rate:

Domestic yaks give birth to single calves in alternate years, but in areas of poor grazing, a few may give birth only once every three years, according to local informants. Wild yaks probably have a similar calving interval. (Schaller 1998)

Early Development:

Weaning takes place about 1 year after birth (Bhatnagar 2002).

Dispersal:

Young become independent after about 1 year.

Maximum Age:

23 years (Bhatnagar 2002).

Diet:

The wild yak grazes on grasses, herbs, mosses, and lichens, and crunches ice or snow as a source of water (Burnie & Wilson 2001).

Behavior:

The wild yak feeds mostly in the morning and evening. Due to the sparseness of vegetation in its environment, the yak must travel long distances to obtain its needed nourishment. It is a sure-footed climber. The wild yak is extremely sensitive to heat and coordinates its seasonal movements with the temperature and food supply. While in the highlands, the wild yak withstands violent winds and snowstorms for hours at a time. It can tolerate temperatures of -40°C (-40°F [Ed. note: Yes, the Fahrenheit and Centigrade temperature scales are the same at -40°!]). It also bathes in lakes and streams in severe cold. The wild yak stays in high areas with permanent snow during the relatively warm months of August and September and spends the rest of the year at lower elevations.

The wild yak is generally wary - if a herd is disturbed, the yaks will flee for a long distance, galloping with their tails held erect (Bhatnagar 2002).

Social Organization:

Most wild yak cows are in large herds with their young with up to 100 or more animals of all ages and usually both sexes. Herds are not stable units: they readily split, or two or more may join. In the Aru Basin, mean herd size (n = 64 herds, excluding solitary individuals) is 24.5 and the median is 58.1; elsewhere in the Chang Tang reserve, mean herd size (n = 109 herds) is 11.3 and the median is 26.5. (Schaller 1998)

The wild yak is highly gregarious. Females and young congregate in large herds, which formerly were reported sometimes to contain thousands of individuals, while adult males spend most of the year alone or in groups of as many as 12. (Tan 1996)

Density and Range:

About 12% of the Chang Tang reserve in Tibet, China is composed of areas of moderate-to-high wild yak density of about 13 sq km/yak (5.0 sq mi/yak). Low-density areas in the reserve may average about 30 sq km/yak (12 sq mi/yak) with an estimated 100 sq km/yak (39 sq mi/yak) in very low density areas. Based on rough calculations, the reserve had a density of about 42 sq km/yak (16 sq mi/yak). (Schaller 1998)