Mule Deer

Common Name: Mule Deer
Class: Mammalia
Order: Artiodactyla
Family: Cervidae
Genus: Odocoileus
Species: Odocoileus hemionus

photo M. Noonan

One of the most distinct features of the Mule Deer is its big "mule-like" ears. These ears move constantly and independently. Surprisingly, despite their big ears, mule deer are thought to rely primarily on their sense of smell in detecting danger (however, their hearing is also extremely acute).

photo M. Noonan

Mule Deer Taxonomy/Description

Mule deer belong to the Mammalian Order Artiodactyla, in the family Cervidae. Other members of Cervidae include, moose, elk, and whitetail deer. The mule deer's scientific name is Odocoileus hemionus, which means "hollowed toothed half-ass". "Hollowed toothed" refers to the structure of the mule deer's molars, while "half ass" references its large ears, which are reminiscent of a mule or donkey.

photo M. Noonan

The mule deer, while closely related to the white-tailed deer, are distinct in many of their attributes. Mule deer are usually a dark grey-brown, with a small white rump patch and a small, black tipped tail. The tail is thin and drooped, unlike the uplifted, bushy white tail of its cousin. The ears of mule deer are proportionately much longer than those of whitetail deer. They are also identifiable by their smaller tail, which is marked by a black dorsal line, and a dark V-shaped mark extending from between their eyes to the top of their head. Mule deer have pheromone producing integumentary glands. These are located at the tarsals, metatarsals, tail, and between the toes. Urine also acts as a pheromone. Mule deer bucks are generally larger than does, and grow dichotomous branching antlers in the spring, shedding them in the winter.

Mule Deer Habitat/Diet

Mule deer prefer coniferous forests, chaparral, desert scrublands, and grasslands throughout the American west and southwest.

photo M. Noonan

Mule deer are browsers, and feed on shrubs, twigs, grass, and herbs. As ruminants, mule deer contain a four chambered stomach which plays an essential role in its digestion of plant matter.

Mule Deer Behavior/Reproduction

Mule deer females (does) reside in clans of maternal descent. Bucks form groups of unrelated members.

photo M. Noonan

The Mule Deer are noted for their particular, high-bounce trot. The predatory escape maneuver exercised by mule deer is unique. Called ‘stotting’, this high bounce trot helps them to pass over rocks and brush at a much faster speed than a running animal can go around them. A mule deer will frequently pause as it flees, stopping to acquire information about the pursuing predator.

photo M. Noonan

The peak breeding period for mule deer is from late November to mid-December. The average gestation period is 204 days. Although twins are common, does in their first or second breeding year produce singletons.

Mule Deer History

Recent analysis of three North American deer species' (mule deer, blacktail deer, and whitetail deer) mitochondrial DNA now allows biologists to hypothesize the mule deer’s unique evolution. This testing determined that blacktail bucks bred with whitetail does to produce mule deer. As whitetail deer spread east to west across prehistoric North America, those reaching the northwest coast ultimately became a separate species, blacktail deer. Thousands of years later, as blacktail deer expanded eastward, whitetail deer once more spread westward, with the two species meeting in the Midwest. The blacktail bucks supplanted the whitetail bucks, breeding with the whitetail does. The resulting hybrid species is known now as mule deer. At this point in time, the blacktail deer is classified as a mule deer subspecies. It is smaller in size than the generic mule deer, and it has a longer tail. The blacktail deer inhabits the Pacific coastline, from Alaska to southern California.

photo M. Noonan

Our Experience with Mule Deer

Our team spotted two mule deer browsing on a grassy hillside as we were leaving Badlands National Park.

Mule Deer Conservation

The greatest threat to the survival of mule deer is the loss of habitat due to human activity, including habitat alteration by agricultural processes, such as cattle grazing. Mule deer may also contract and/or spread diseases that plague domesticate cattle, including Hoof and Mouth Disease (HMD).

photo M. Noonan


Artiodactyla – Mammalian Order meaning "even toed", which consists of all even-toed hoofed mammals, including families that contain cattle, antelope, deer, camels, and hippopotamuses

browser – animal that selectively feeds on leaves

chaparral – a dense thicket of shrubs or small trees, especially of evergreen oaks in southern California

dichotomous – the basic structure of the antler is supported by two main beams, with smaller tines protruding off, as opposed to whitetail deer antlers, upon which tines project from a single main beam

Hoof and Mouth Disease (HMD) – transferable among all cloven hoofed mammals; symptoms include fluid filled sacs on the oral mucosa and feet

Content provided by Canisius College students under the direction of Michael Noonan, PhD.