Mule deer are “mule-like” in that they have large ears that seem to be constantly moving, and are about ¾ the length of their head. Their unique bounding movement is stiff-legged and almost a hop where all four feet seem to leave the ground at the same time. This contrasts to the gallop-type movement of other members of the deer family in North America. They are grayish in winter but reddish to yellowish-brown in summer. They have a white throat patch and a rumppatch that is white to yellowish. Their tail is black tipped. Males have antlers in which the main beam divides somewhat equally which can divide again forming points or tines. Bucks weigh from 110 to 475 pounds (50-215 kg), and females weigh between 70 and 160 pounds (32-66 kg).
This species ranges from southeastern Alaska, south through Canada and most of western U.S. and Great Plains, to Baja California and the southern end of the Mexican Plateau. They do range east to the western edge of Minnesota. They are common throughout the intermountain West and the northern Rockies in a diversity of habitats.
Mule deer are found in coniferous forests, shrub steppe, chaparral , and grasslands with shrubs, from dry, open country to dense forests. Often associated with early successional vegetation or vegetation resulting from disturbance, especially near agricultural lands. However, in southeastern Alaska, uses old-growth forests almost exclusively in winter and spring. In Idaho, prefers rocky brushy areas, open meadows, open pine forests, and burns.
They browse on a wide variety of woody plants, primarily during the winter when snows cover grasses and forbs . Common browse plants include sagebrush, aspen, dogwood, juniper and Douglas fir. They graze on various grasses and forbs heavily during spring, summer and fall. They do occasionally feed on agricultural crops. Some studies have suggested that in the Rocky Mountains, their diet may be nutritionally inadequate during at least part of the year. They do require open areas that provide a diversity of grasses and forbs , and this is not always available in forested country.
Throughout year, most of their activity occurs at dawn and dusk, although nocturnal and daytime activity is common. Their home range size may be 36 to 243 ha or more; size is directly correlated with availability of food, water, and cover. In the Pacific Northwest, deep winter snows are major factors limiting population size. An Idaho study found that deer showed a high fidelity to their summer range, but less so to their winter range; deer from one summer range migrated to different winter ranges. Mule deer migrate from high, mountainous country to lower valleys and foothills during late fall to avoid heavy snow. They are a primary prey of mountain lions, and smaller mule deer are preyed on by coyotes, bobcats, and occasionally golden eagles. They are very common in Idaho and throughout the intermountain West. Bucks tend to be solitary or in small groups (2 to 4) during the rut. Does and their young (fawns and yearlings ) tend to stay together as a family group but remain separated from other similar family groups. Mule deer do herd during the winter in specific areas having a good combination of shelter and food. Severe winter conditions can reduce their populations drastically. This is probably the most common large game animal in Idaho and thousands are shot by hunters each year.
The breeding season, or rut , peaks in mid-November to mid-December. gestation lasts about 203 days. In much of their range, young are born mostly in May and June; but July and August births occur in some areas. They typically have one or two fawns , depending on the age and condition of the female. Weaning begins at about 5 weeks, and is usually completed by week 16. Females usually breed at 2 years, males at 3 to 4 years.
Important State References:
Brown, C.G. 1992. Movement and migration patterns of mule deer in southeastern Idaho. J. Wildl. Manage. 56:246-253.