The domestic yak (Bos grunniens), also known as the Tartary ox, grunting ox,[1] or hairy cattle,[2] is a species of long-haired domesticated cattle found throughout the Himalayan region of the Indian subcontinent, the Tibetan Plateau, Gilgit-Baltistan (Kashmir), Tajikistan and as far north as Mongolia and Siberia. It is descended from the wild yak (Bos mutus).[3]
The English word yak originates from the Tibetan: གཡག་, Wylie: g.yag. In Tibetan and Balti it refers only to the male of the species, the female being called Tibetan: འབྲི་, Wylie: bri, Tibetan: འབྲི་, Wylie: dri or Tibetan: གནག, Wylie: g.nag in Tibetan and Tibetan: ཧཡག་མོ་, Wylie: hYag-mo in Balti. In English, as in most other languages that have borrowed the word, yak is usually used for both sexes, with bull or cow referring to each sex separately.
Belonging to the genus Bos, Yaks are related to cattle (Bos primigenius). Mitochondrial DNA analyses to determine the evolutionary history of yaks have been inconclusive.
The yak may have diverged from cattle at any point between one and five million years ago, and there is some suggestion that it may be more closely related to bison than to the other members of its designated genus.[4] Apparent close fossil relatives of the yak, such as Bos baikalensis, have been found in eastern Russia, suggesting a possible route by which yak-like ancestors of the modern American bison could have entered the Americas.[5]
The species was originally designated as Bos grunniens ("grunting ox") by Linnaeus in 1766, but this name is now generally considered to refer only to the domesticated form of the animal, with Bos mutus ("mute ox") being the preferred name for the wild species. Although some authors still consider the wild yak to be a subspecies, Bos grunniens mutus, the ICZN made an official ruling in 2003[6] permitting the use of the name Bos mutus for wild yaks, and this is now the more common usage.[7][5][8]
Except where the wild yak is considered as a subspecies of Bos grunniens, there are no recognised subspecies of yak.