The yak lives high in the mountains in extreme cold, high altitude low oxygen environments. Temperatures in these areas are extremely important.
The yak copes with the extreme cold by conserving its heat. It does not generate heat (because this action requires food, and food is hard to come by in these areas). They conserve heat within their thick fleece of rough outer hair, and a finer undercoat.
Their bodies are also designed to handle the cold. They have short limbs, small necks, small ears, tail, and unwrinkled skin.
Just before winter, the yak gets a layer of fat that comes right beneath its skin. This acts as an energy reserve as well as an extra coat to keep him warm.
Their skin is very thick and has many sweat glands that do not really function (because of the low temperatures). However, this also means that they find it difficult to tolerate higher temperatures.
Their environment has low oxygen content. The yak’s body has adapted to this condition by having a very large chest, with about 14 to 15 pairs of ribs, a large set of lungs, and a equally large heart to pump blood to its compact body.
Most yaks have black fur coats, and their skin has a high level of pigmentation. Both these features help them to adapt to the high solar radiation in their environment.
Their large hooves and heads allow them to forage just about anything. They graze on grass, shrubs, sedges, and even on coarse plants, rapidly and for a long time, using their hooves and head to wade through obstacles.
The yaks prefer to stay in herds, for protection against predators. However, their temperaments allow them to adapt to potentially dangerous situations, by never backing down if they are frightened – they will fight.
As the seasons change, so do the growth of their fleece. During winter, their down fibers (just below the main coat) grow thick and long. During summer, these hairs slowly shed.
The yak has an amazing ability to walk on the rough terrains that horse or sheep find difficult to do. This is because they have very strong limbs, but small hooves with narrow sharp tips. If they are in danger of sinking in a marsh, they spread their legs out and rely on their bellies, to save them.