The needs of mule deer vary with conditions and seasons. The ideal habitat for mule deer usually contains steep and rugged topography with brushy draws, rocky outcrops and quick access to escape routes.
Mule deer will remain in the same area if all their habitat needs are met. However, long migrations may occur as the seasons change if an area does not meet all the habitat requirements. When the habitat meets the deer's needs, seasonal home ranges may be as small as one square mile. In general, the ideal mule deer habitat has about 40 percent of the area providing cover and 60 percent forage. Half of the cover should be composed of hiding cover, and the remaining half should be equally divided between thermal cover and fawn-rearing habitat. The more interspersed the cover and foraging habitat, the more valuable or higher quality the habitat. A mosaic of plant communities and topographic conditions will be much more valuable for mule deer than a habitat with completely seperate areas for cover and foraging.
Components of Foraging Habitat
Mule deer diets vary according to the season. In winter, south-facing slopes that are free of snow (or at least have less snow) are most attractive. In summer, cool shaded slopes or an area with a breeze to deter biting insects will be most attractive. The idea of attractiveness can also include seclusion, protection from wind or a combination of factors.
Naturally, water is an important feature, ensuring that mule deer digest their food well and achieve proper nutrition. Water should be within one-half to one mile from deer feeding areas. A number of small dispersed watering points are preferable to a few large ones. It is important to make livestock watering points available to deer even when livestock are not using them.
Mule Deer diets change with the seasons:
- Spring forage includes early-greening grasses and forbs that are highly palatable, succulent and nutritionally rich. Idaho fescue, bluebunch wheatgrass, prairie clover, milkvetch and alfalfa are species important to mule deer in spring.
- During summer, forbs may make up as much as two-thirds of the mule deer diet. As grasses and forbs dry up in late summer, deer consume more shrubs. Important browse plants include serviceberry, mountain mahogany, currant, bitterbrush, willow and quaking aspen.
- During fall, forbs will be used as long as they are available and may make up 25 percent of the diet. Woody browse becomes increasingly important as mule deer put on fat stores in preparation for winter.
- Winter diets are made up of 75 percent browse species where shrubs are available. Some cured grasses are used, and forbs are sought until they are dead or covered by snow. The availability of browse species such as quaking aspen, mountain mahogany and bitterbrush can be extremely important.
The kinds of food available are as important as the amount of food. Juniper and sagebrush can help prevent starvation when no other foods are unavailable, but they do not have a good nutritional value for mule deer. Sagebrush should never be more than 15-20 percent of the diet for extended periods because it contains many volatile oils and chemicals that inhibit the microorganisms in the stomach (rumen) from digesting the food.
Components of Cover Habitat
- Escape cover is used by mule deer whenever an immediate threat is perceived. Mule deer prefer open, broken country where they can detect danger at a great distance. Mule deer do not usually escape predators through long extended runs but rather through short bursts of speed to reach the security found in rough terrain or dense vegetation.
- Loafing cover is where mule deer spend most of their time, including time spent sleeping, resting and ruminating between periods of feeding and traveling. These areas are usually chosen because of comfort attributes that vary throughout the year. For example, loafing cover will have breezy ridges for relief from insects during the summer and will also contain observation points, such as knolls or benches, that allow deer to see approaching danger. Loafing areas are close to escape cover and provide seclusion from human disturbance.
- Thermal cover protects deer from cold winter temperatures and summer heat. It is provided by rough topography and southern exposures. Tall shrubs and small evergreen trees can break the wind and minimize radiant heat loss. Patches of thermal cover should be two to five acres in size. Vast areas of potential mule deer habitat are unusable if there is no thermal cover.
- Fawning cover combines areas of closely interspersed escape cover, hiding cover, along with water sources and high quality forage areas. Ideal fawning cover consists of two to five acre patches of low shrubs or small trees two to six feet tall with overstory tree cover. A number of scattered fawning cover areas are necessary to prevent predators, especially coyotes, from keying in on fawns.
Habitat Management Suggestions
Cultivated lands, when available near cover, offer prime opportunities to grow the foods that attract, support and produce good to excellent deer populations. Landowners who want deer and deer hunting should plant, establish or make available a number of choice foods listed above under "Foods."
Management of rangelands for mule deer must consider dual and competitive uses of important forage species by domestic livestock. Use of a range is usually determined by examining the percent of annual growth of plants eaten by animals. Thus, as a rule of thumb, we know that forage is being utilized too heavily when more than 50% of the available annual growth of key shrub species, such as bitterbrush or mountain mahogany, has been consumed. In such cases, either livestock or deer numbers should be reduced - by seasonal management of the livestock, or by increased harvest of deer through hunting. Mule deer do not prefer cured grasses, so proper grazing of grasslands by cattle is not detrimental to mule deer. Sheep and goats, however, are much more competitive with mule deer. To recognize proper use, overuse and general range conditions, an experienced range conservationist, biologist or soil conservationist can be helpful.
Woodland habitat in mountainous mule deer range usually accumulates deep snow in the late fall and winter, and deer must migrate into the foothills and lower elevation rangelands for winter forage. This is a critical period for deer and the season when high death losses are most common.