Desert Mule Deer

Desert Mule Deer, Odocoileus hemionus eremicus

Desert Mule Deer, Odocoileus hemionus eremicus. Deer photographed within the confines of the Arizona-Sonora Desert Museum, Tucson, Arizona, February, 2022.

The Desert Mule Deer, Odocoileus hemionus eremicus, is a member of the Cervidae family of Deer. The Cervidae family consists of forty-three members placed in three subfamilies and nineteen genera. At present there is ongoing debate over the classification of the Cervidae family within the scientific community. There are two species in the Odocoileus genus. The Desert Mule Deer is one of eleven subspecies of the Mule Deer, Odocoileus hemionus. The Desert Mule Deer are known in Mexico as Ciervo Bura Del Desierto.

Desert Mule Deer can easily be identified by their large ears that move independently from one another. They are brownish-gray in color with a white rump patch. Their tails are small and white with a black tip. Sexual dimorphism is displayed with males growing antlers during the summer and fall, and shedding them each spring. Their antlers split off from the main branch, forming two additional branches that each have two or more tines. Antler size is influenced by age, level of nutrition, and genetics. Male Desert Mule Deer grow larger than the females, ranging from 0.9 m (3 feet 0 inches) to 1.1 m (3 feet 6 inches) in height at the shoulder and 1.4 m (4 feet 6 inches) to 2.1 m (7 feet 0 inches) in length. Their tail is 13 cm (5 inches) to 20.3 cm (8 inches) in length. They weigh between 59 kg (130 lbs) and 127 kg (280 lbs).

Desert Mule Deer breeding season, or rut, extends from mid-November through mid-February, peaking in December. During rut, males expend vast reserves of energy to fight off competing suitors. Behaviors associated with rut include head-tossing, rub-urination, antler thrashing and forehead rubbing, and chasing. Head-tossing involves a rapid lifting of the head and muzzle, often accompanied by a snort. Rub-urination occurs when a buck rubs his tarsal glands together and urinates on them when threatening or dominating another buck. A combination of antler thrashing followed by rubbing of the forehead on vegetation is observed in all antler classes of bucks, with larger bucks thrashing more frequently. Chasing is closely associated with the peak of rut and involves rapid movement of one male toward another with their head up and ears upright. Sparring is observed during the start of the mating season, decreases in frequency during rut, and becomes more frequent as rut wanes. During sparring, two bucks approach each other, lower their heads, carefully join antlers, and begin pushing forward in an attempt to drive their opponent back or push him off balance. Desert Mule Deer are social and form multigenerational family groups of related females. Courtship and mating takes place within these groups, with one dominant buck generally allowing no other buck to court. He will tolerate subordinate males in the group only if they pay no attention to the females. Although one female at a time is courted, Desert Mule Deer still maintain a highly polygynous breeding system, with the few most dominant bucks responsible for most of the copulations. Gestation is approximately 7 months (210 days), and most births occur in July and August. Females generally give birth to single fawns the first time they breed and twins are common thereafter, if foraging conditions are adequate. Desert Mule Deer become sexually mature at two years of age and attain maximum body size at six years. Females typically remain with their family group, while bucks older than one year often leave their family groups and travel independently or in small groups with other bucks. They have life spans of fifteen to twenty years in captivity and eight years in the wild.

 Desert Mule Deer primarily consume forbs and browse. They primarily rely on forbs during the spring in summer, and browse during the fall and winter. Additionally, Desert Mule Deer consume grasses, fruits, nuts, and succulents. They are regularly preyed upon by Coyotes and Mountain Lions, and occasionally by Bobcats, Black Bears, and domestic Dogs. In addition, the Desert Mule Deer is an important game species in the United States and Mexico. 

Desert Mule Deer are found in the lower Colorado River Valley from southeastern Texas, across southern New Mexico and Arizona, and South into north central Mexico. They inhabit a variety of desert regions, as long as there is enough vegetation to hide in and eat. They move to higher elevations during the hottest parts of the summer and return to lower elevations during the winter months. Additionally, they are found in mountain forests, wooded hills, and chaparral landscapes. 


From a conservation perspective, the IUCN currently includes all Mule Deer species under the same listing so the exact status of this subspecies is unclear. Overall Mule Deer are considered to be of Least Concern due to their adaptability to a wide range of habitats, large populations, occurrence in numerous protected areas, with stable populations. Currently, the most urgent threat to Mule Deer in the wild is the spread of Chronic Wasting Disease (CWD), a transmissible spongiform encephalopathy (TSE). CWD is more prominent at the local or regional level, and has currently been diagnosed in Mule Deer in the Rocky Mountains region of the United States and other mid-western states. Other threats to Mule Deer include high predator populations, competition with livestock for grazing, human habitat alterations, and other anthropogenic disturbances. The trophy hunting of Desert Mule Deer does not currently pose a threat to the species.