Antlers are the usually large an complex horn-like appendages of most deer species, mostly worn by males only, for some species such as caribou by both sexes. They consist of bony outgrowths from the head with no covering of keratin as is found in true horns. Each antler grows from an attachment point on the skull called a pedicle. While an antler is growing it is covered with highly vascular skin called velvet, which supplies oxygen and nutrients to the growing bone; once the antler has achieved its proper size, the velvet is lost and the antler's bone dies. This dead bone structure is the mature antler. Antlers shed after each mating season.