Bos grunniens
Wild yaks spend their whole lives above the winter line, where wind chill drops below anything most mammals could survive. A dense undercoat and a long, hanging skirt of guard hair shield them, and their lungs and blood are built to squeeze oxygen from thin mountain air.
Fewer than 15,000 truly wild yaks remain, roaming the Tibetan Plateau in herds of cows and calves while old bulls live alone or in bachelor groups. Domesticated yaks, far more numerous, are the backbone of highland life — hauling loads, giving milk, and warming homes with dung fires.