The yak belongs to the same cow family as the Asian water buffalo, the African buffalo and the American bison. However, the yak is slightly more like the American bison in appearance as both the yak and the bison have long hair in order to withstand the colder climates, the bison of the North American winters and the yak of the mid-Asian mountains.
The yak breeds in the warmer months of September and after a gestation period of nine months the female yak gives birth to a single yak calf. A female yak will occasionally give birth to twins but it is very rare. Some female yak give birth to a calf almost every year but it depends on the environment in which the yak lives and the yak individual. Yak babies are completely independent by the time that they are a year old and they are fully grown when they are between 7 and 8 years old. The average lifespan of a yak is about 20 years in the wild and slightly longer when in captivity.
Like other species of cow, the yak is a herbivore and spends a great deal of time on grassy plains in the mountains grazing on grasses, herbs and wild flowers. In a similar way to other cow species the yak has more than one stomach which the yak uses to successfully get all of the nutrients out of the plants that it eats. The yak has firm, dense horns which the yak uses to break through snow in order to get the plants that are buried beneath it and the yak will also use it's horns in defence. They have long shaggy hairthat covers their bodies that keep them warm and dry.