Mule deer commonly share their range with other grazing animals such as domestic livestock, other big game (white-tailed deer, pronghorn antelope, elk) and/or exotic game species such as aoudads. An understanding of the diets of each of these herbivores is important in determining the potential for competition between different species of animals (Fig 6). Mule deer eat primarily browse and forbs with grass important only in the early spring. Cattle consume primarily grass, with forbs and browse as secondary but seasonally important components. Sheep eat more browse and forbs than cattle, but less than deer. Goats have essentially the same diets as do deer. Therefore, the potential for competition with deer is greatest from goats, less from sheep, and least from cattle. During dry years, however, all kinds of livestock tend to consume more browse, thus compounding the degree of competition with deer.
In some areas, elk and aoudads are also common neighbors of the mule deer. Elk and aoudads have broad feeding inches, consuming grass, forbs and browse as they are seasonally abundant. Therefore, these big game species can be quite competitive with mule deer for forage. A disconcerting fact is that elk and aoudads have the flexibility to shift their diets from forbs to browse to grass as the more preferred forage class becomes limited. Mule deer lack such flexibility in their diets. Pronghorn antelope have diets similar to domestic sheep, but tend to inhabit more open country than do mule deer; thus the potential for competition is minimal.