The mule deer is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. Two subspecies of mule deer are grouped into the black-tailed deer.
Unlike the related white-tailed deer, which is found throughout most of North America east of the Rocky Mountains and in the valleys of the Rocky Mountains from Idaho and Wyoming northward, mule deer are only found on the western Great Plains, in the Rocky Mountains, in the southwest United States, and on the west coast of North America. Mule deer have also been introduced to Argentina and Kauai, Hawaii.
The most noticeable differences between white-tailed and mule deer are ear size, tail color, and antler configuration. In many cases, body size is also a key difference. The mule deer’s tail is black-tipped, whereas the white-tailed deer’s is not. Mule deer antlers are bifurcated; they “fork” as they grow, rather than branching from a single main beam, as is the case with white-taileds.
Each spring, a buck’s antlers start to regrow almost immediately after the old antlers are shed. Shedding typically takes place in mid-February, with variations occurring by locale. Although capable of running, mule deer are often seen stotting (also called pronking), with all four feet coming down together.
The mule deer is the larger of the three Odocoileus species on average, with a height of 31–42 in at the shoulders and a nose-to-tail length ranging from 3.9 to 6.9 ft. Of this, the tail may comprise 4.6 to 9.1 in. Adult bucks normally weigh 121–331 lb, averaging around 203 lb, although trophy specimens may weigh up to 460 lb. Does are smaller and typically weigh from 95 to 198 lb, with an average of around 150 lb.
Unlike the white-tailed, the mule deer does not generally show marked size variation across its range, although environmental conditions can cause considerable weight fluctuations in any given population. An exception to this is the Sitka deer subspecies. This race is markedly smaller than other mule deer, with an average weight of 120 lb and 79 lb in males and females, respectively.