Each year, deer produce two coats of hair, each adapted to a particular climate. In the late spring, whitetail deer grow a coat of short, fine, reddish hair, which permits adequate air circulation for summer temperatures. In the fall, the whitetail molts to a more insulative coat, comprised of dense layers of wooly hair under a layer of long, hollow guard hairs, which can be erected to form a thick, insulated coat that will protect against winter temperatures in Maine.