white-tailed deer, (Odocoileus virginianus), also called Virginia deer, common American deer of the family Cervidae (order Artiodactyla) that covers a huge range from the Arctic Circle in western Canada to 18 degrees south of the Equator in Peru and Bolivia. The white-tailed deer get its name from the long white hair on the underside of the tail and rump. During flight the hair is flared, and the tail is held aloft like a signaling flag. It belongs to the subfamily of New World deer. Although the white-tailed deer of North and South America are currently recognized as one species, genetically these deer are further apart than are white-tailed and black-tailed deer in North America.