The Mule Deer, while closely related to the eastern species of the white-tailed deer, are remarkably distinct in their biological, ecological, and behavioral attributes. Mule Deer have large ears that move constantly and independently, from whence they get their name, "Mule" or "Burro Deer."
Mule Deer are active primarily in mornings, evenings and moonlit nights. During the middle of the day, the Mule Deer beds down in a cool, secluded place. The mature buck seems to prefer rocky ridges for bedding grounds, while the doe and fawn is more likely to bed down in the open. Mule Deer is an excellent swimmer, but water is rarely used as a means of escaping predators.
The annual cycle of antler growth in Mule Deer is initiated and controlled by changes in day length acting on several cell types of the anterior pituitary. While unable to detect motionless objects, Mule Deer is extraordinarily sensitive to moving objects. The Mule Deer sense of hearing is also extremely acute. For Native Americans and early European settlers, deer meat (venison) provided one of the most important sources of protein. Sport hunters kill about 1 million Mule Deer and 2 million White-tailed Deer annually.