 When you think of elk, deer, and moose, images that come to mind probably include a rack of antlers. Would you believe that these fall off every winter and regrow again by fall? Antlers are unique to members of the Servid family and are mostly seen on males. The larger antler size helps males as they fight to establish who is dominant and increase their female mate selection. Antlers grow larger each year until they pass their prime and begin to decline. Antlers are made of true bone and are the fastest growing bone of all mammals. Antlers begin growing in the spring. As they grow, they are covered with a skin called velvet that contains numerous blood vessels which supply the bone with oxygen and nutrients. As testosterone levels increase in late summer, the antler reaches its maximum size. The bone then dies and the velvet falls or is rubbed off. After mating season, testosterone levels drop causing the antler to fall off. Prong horns horns have some characteristics of antlers but are not antlers because they contain keratin. Since antlers are shed every winter, a popular recreational activity in the spring is shed hunting to find these discarded trophies. From the University of Wyoming Extension, I'm Mae Smith, Exploring the Nature of Wyoming.