In high altitudes (10,500-18,000ft,) wild yaks graze on unaffected Himalayan grasses, herbs, and lichens. Well-adapted for harsh highlands, wild yaks have efficient lungs, thick coats, and nimble feet to travel rough terrain. Their blood cells are 50% smaller than those of cattle and 300% more numerous, permitting greater systemic oxygen abundance. Thick coat and fewer sweat glands retain heat efficiently in -40 C temperatures. In single file, herds traverse snow carefully tracing the previous yak leader footprints.