The mule deer can be found from the southern Yukon in Canada; throughout the western United States into Texas, including the Panhandle; and east to Wisconsin. Its primary habitats are forest edges, mountains, and foothills.

In summer, its stocky body supported by sturdy legs sports a coat that is reddish or yellowish-brown; in winter the coat turns grayish.

An adult mule deer stands between 90 and 105cm high at the shoulder. The males weigh as much as 215 kg; females as much as 72 kg.

These deer have large ears that move independently of one another, almost constantly, which accounts for its common name.

Primarily active in mornings, evenings, and on moonlit nights, mule deer may also be active at midday in winter.

In summer, it eats mostly plants, but also blackberry, huckleberry, and thimbleberry; in winter, its diet includes twigs of Douglas fir, cedar, aspen, willow, dogwood, serviceberry, juniper, and sage.  Mule deer may also eat acorns and apples.

All Mule Deer have glands on the hind legs above the hooves. A fawn seems able to recognize its mother by these glands, and when deer are in groups, the glands are frequently sniffed.