Mature bulls usually shed their antlers shortly after the rut, whereas cows can keep theirs until spring. Their dense coat varies in colours from cream, brown and grey. Their wide splayed hoofs provide support across the snow (snow shoes) and act like paddles when swimming. They have specialised noses that dramatically increase the surface area within the nostrils. Incoming cold air is warmed by the animal's body heat before entering the lungs, allowing them to live in such cold conditions.