Mule Deer live in a broad range of habitats - forests, deserts, and brushlands. Mountain populations migrate to higher elevation in warmer months, looking for nutrient-rich new-grown grasses, twigs, and shrubs. They maintain separate summer and winter ranges, connected by a migratory pathway. In milder climates, they do not migrate. They live in small social groups of about three, except during the winter, when large groups may come together to feed in open meadows. Females tend to stay close to where they were born. Males disperse farther, establish their own territories, and compete for access to females during the October and November breeding season. The males lose their antlers after breeding and grow new ones yearly, with each set becoming larger than the previous one. Newborns, with spotted coats, are well-camouflaged.

Adaptation: The remarkable evolution of running adaptations is evident in comparing the same (homologous) wrist and hand bones of the Mule deer, Odocoileus hemionus (image on the left), with a primitive type of versatile hand, like that of a Hedgehog, Erinaceus europaeus (image on the right).

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Odocoileus hemionus occurs throughout western North America from Alaska and Western Canada through the Rocky Mountains and Western Plains States of the United States south to the Peninsula of Baja California, Cedro Island, Tiburon Island and Northwestern Mexico. The southernmost distribution reaches central Mexico, but the historical boundary is not very clear (Sanchez- Rojas and Gallina 2007)

Odocoileus hemionus occurs over most of North America west of the 100th meridian from 23 degrees to 60 degrees N. The eastern edge of the usual range extends from southwestern Saskatchewan through central North and South Dakota, Nebraska, Kansas, and western Texas. Isolated occurrences have been reported from Minnesota, Iowa, and Missouri. Major gaps in geographic distribution are in southern Nevada, southeastern California, southwestern Arizona, and the Great Salt Lake desert region. Apart from these gaps, O. hemionus occurs in all of the biomes of western North America north of central Mexico, except the Arctic tundra (Anderson 1984).

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Native range extends from southeastern Alaska south through Canada and most of the western United States and Great Plains, to Baja California (including some islands in the Sea of Cortez) and the southern end of the Mexican Plateau (Sonora and northern Tamaulipas, according to Grubb, in Wilson and Reeder 1993). The species has been introduced in Hawaii (Tomich 1986) and Argentina.

The pelage of Odocoileus hemionus ranges from dark brown gray, dark and light ash-gray to brown and even reddish. The rump patch may be white or yellow, while the throat patch is white (Geist 1981). The white tails of most mule deer terminate in a tuft of black hairs, or less commonly in a thin tuft of white hairs. On some mule deer, a dark dorsal line runs from the back, down the top of the tail, to the black tail tip. All markings vary considerably among O. hemionus, but remain constant throughout the life of an individual. O. hemionus possess a dark V-shaped mark, extending from a point between the eyes upward and laterally. This mark is more conspicuous in males. Growth in O. hemionus during the first year is roughly parallel in males and females. Thereafter, males, in general, exceed females in carcass weight, chest girth, neck circumference, body length, head length, cranial breadth, shoulder height, hindfoot length, and hoof length (Anderson 1984). Carcass weight ranges from 45 to 150 kg in males, and 43 to 75 kg in females. Chest girth ranges from 80 to 117 cm in males, and 78 to 97 cm in females. Neck circumference ranges from 30 to 65 cm in males, and 26 to 38 cm in females. Body length ranges from 126 to 168 cm in males, and 125 to 156 cm in females. Head length ranges from 28 to 35 cm in males, and 27 to 33 cm in females. Cranial breadth ranges from 11 to 16 cm in males, and 10 to 14 cm in females. Shoulder height ranges from 84 to 106 cm in males, and 80 to 100 cm in females (Wallmo 1981).

Range mass: 43 to 150 kg.

Sexual Dimorphism: "Males are usually heavier than females. "

Length:
Range: 1.3-1.7 m males; 1.3-1.6 m females

Weight:
Range: 40-120 kg males; 30-80 kg females

Length: 199 cm

Weight: 215000 grams

Habitat and Ecology

Systems

• Terrestrial

Odocoileus hemionus is remarkably adaptable. Of at least sixty types of natural vegetation west of the 100th meridian in the United States, all but two or three are or once were occupied by O. hemionus. Several additional vegetation types are inhabited in Canada and Mexico as well. The vegetation types in Mexico are similar to the types occurring in the United States. However, the tropical deciduous vegetation at the tip of Baja California is unique. In Canada, O. hemionus occupies five boreal forest types that do not occur in the United States. O. hemionus occupies a wide range of habitat provinces (regions of land containing particular vegetation types) in western North America. These habitat provinces include the California woodland chaparral, the Mojave Sonoran desert, the Interior semidesert shrub woodland, the Great Plains, the Colorado Plateau shrubland and forest, the Great Basin, the Sagebrush steepe, the Northern mountain, and the Canadian boreal forest (Wallmo 1981).

Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral ; forest ; mountains

Comments: Mule deer occupy many types of habitats in mountains and lowlands, including various forests and woodlands, forest edges, shrublands, grasslands with shrubs, and residential areas. They are often associated with successional vegetation, especially near agricultural lands, but in southeastern Alaska they use old growth forests almost exclusively in winter and spring (Schoen and Kirchhoff 1990). In winter, mule deer tend to be on warmer slopes or other areas with minimal snow cover. Populations in Hawaii occur in moderately dry native and introduced forest.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

In mountainous regions, tends to migrate (up to 100+ km) from high summer range to lower winter range. In southeastern Alaska, migrated from low elevation heavily forested winter range to higher elevation summer range in open canopy subalpine and alpine habitats (Schoen and Kirchhoff 1990). In arid southwest, may migrate in response to rainfall patterns. Generally not migratory on plains. Exhibits high fidelity to individual seasonal ranges (e.g, see Kucera 1992).

Odocoileus hemionus is a small ruminant with limited ability to digest highly fibrous roughage (Short 1981). Optimum growth and productivity of individuals and populations are dependent upon adequate supplies of highly digestible, succulent forage. Diets consisting primarily of woody twigs cannot meet the maintenance requirements of O. hemionus. Based on its stomach structure and its diet of woody and herbaceous forage in approximate equal proportions, O. hemionus is classified as an intermediate feeder. Because nutritious forage is in poor supply for much of the year, O hemionus has an annual cycle of metabolic rates. A higher energy flux and food intake in the summer enables O. hemionus to capitalize on abundant high-quality forage for growth and fat storage. A lower energy flux in the winter permits O. hemionus to survive on a lower intake of poor-quality forage while minimizing the catabolism of stored fat for body functions. The estimated rate of food intake is about 22 g/kg body weight/day. In adult males, food intake drops abruptly with the onset of rut (Anderson 1984). O. hemionus frequently browses leaves and twigs of trees and shrubs. Green leaves are very succulent and, except for epidermal tissue and structural ribs, consist largely of easily digestible cell contents. Dead and weathered leaves have little protein and high cell-wall values. As a result, they are of very low digestibility. O. hemionus also eats acorns, legume seeds, and fleshy fruits, including berries and drupes, that have moderate cell-wall levels and are easily digested (Short 1981).

Comments: Browses on wide variety of woody plants and grazes on grasses and forbs. May feed on agricultural crops. Also commonly consumes mushrooms, especially in late summer and fall (Great Basin Nat. 52:321). In northern California, reproductive success apparently was reduced due to selenium deficiency (Flueck, 1994, Ecology 75:807-812).

Odocoileus hemionus (bighorn sheep, wapiti, mule deer) is prey of:
Gulo gulo
Ursus arctos

Based on studies in:
USA: Montana (Tundra)

This list may not be complete but is based on published studies.

Odocoileus hemionus (bighorn sheep, wapiti, mule deer) preys on:
alpine vegetation

Based on studies in:
USA: Montana (Tundra)

This list may not be complete but is based on published studies.

Home range size may be 30-240 hectares or more; directly correlated with availability of food, water and cover. Deep winter snows are major factor limiting population size in Pacific Northwest (Schoen and Kirchhoff 1990). Predators include: mountain lions; coyotes; dogs.

See Hatter and Janz (1994) for information on apparent demographic changes associated with wolf control on northern Vancouver Island.

Mule deer males use glands on their forehead to apply scent marks to trees. These scent posts communicate the presence and physiological status of the deer and seem to be important in the social and reproductive biology of the species.

Comments: Throughout the year most activity occurs at dawn and dusk, though nocturnal and daytime activity is common.

Males grow antlers from late winter (March) through summer and into fall (October). Antler shedding occurs from December through April (mostly January-February).

Average lifespan

Status: captivity: 22 years.

Maximum longevity: 22 years (captivity) Observations: One captive female lived 20.5 years (Richard Weigl 2005). A semicaptive reportedly lived 22 years (Ronald Nowak 1999).

Odocoileus hemionus is a polygynous species, having a tending-bond type breeding system. Courtship and mating occur within the group (Geist 1981). A dominant male tends an estrus female until mating or displacement by another male occurs. Dominance is largely a function of size, with the largest males, which possess the largest antlers, performing most of the copulations (Kucera 1978). Most O. hemionus females conceive during their second year and only rarely during their first year. The breeding peak in O. hemionus occurs mainly from late November through mid-December. The average gestation length is 204 days. The peak birth period in O. hemionus is estimated to be from June 16th to July 6th, with most births occurring in June. The time of birth varies according to the environment. Robinette (1977) calculated that a 305-m rise in elevation is associated with a 7-day delay in the birth period. The mass at birth of O. hemionus ranges from 2 to 5 kg. Mass at birth is affected by litter size and sex, with males being heavier. The common liter size is two, with mothers in their first or second breeding year most frequently producing singletons. Weaning begins at about 5 weeks of age and usually is completed at age 16 weeks. Full development of most skeletal attributes occurs at about 49 months of age in males and 37 months of age in females. However, gains in carcass mass are continuous until an age of 120 months in males and 96 months in females. In O. hemionus, male neonates predominate when poor nutrition prevails about 6 weeks before, and during, the breeding period. Ovulation in female O. hemionus occurs about 12 to 14 hours after estrus terminates. Approximately 27 to 29 days elapse between conception and implantation in female O. hemionus. Among male O. hemionus, testicular mass and volume are maximal during November and minimal during April and May (Anderson 1984).

Average birth mass: 2950 g.

Average gestation period: 207 days.

Average number of offspring: 1.5.

Average age at sexual or reproductive maturity (male)

Sex: male: 503 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 478 days.

Mule deer mate in autumn, often mainly late November to mid-December. Gestation lasts about 203 days Births occur in late spring, mostly in May-June in much of the range, sometimes as late as July or August. Litter size is 1-2, depending on age and condition of female. Fawns are born with spotted pelage and initially stay hidden. They lose their spots generally by late summer or early fall. Weaning begins at about 5 weeks, usually completed by 16 weeks. Males usually first breed at 2 years, males at 3-4 years.

The following is a representative barcode sequence, the centroid of all available sequences for this species. 

 
There is 1 barcode sequence available from BOLD and GenBank.   Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen.  Other sequences that do not yet meet barcode criteria may also be available.
 

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Species: 12
Species With Barcodes: 1

All federal, state, and provincial land and wildlife management agencies recognize the fundamental need to maintain O. hemionus ranges and keep them habitable. To counter the trend of agricultural development, rangeland conversion, mining, road and highway construction, and the development of housing tracts, many states and provinces have purchased critical areas, especially winter ranges, to maintain the various habitats of O. hemionus. But, due to political opposition to government acquisition of privately owned lands, plus a scarcity of funds for this purpose, only a small fraction of O. hemionus ranges has been acquired by the government. The effects of reduced O. hemionus ranges can be mitigated by better management of the remaining lands to maximize their productiviy for O. hemionus. Various habitat management programs include the manipulation of livestock grazing, the manipulation of cultivative communities, and the manipulation of vegetative communities. For O. hemionus, the optimal successional stages are subclimax plant communities that can be perpetuated only through the influence of humans. Since O. hemionus production is not the primary management goal on most private or public lands in western North America, O. hemionus habitat improvement programs typically involve a complex process of coordination among bureaucracies with missions that are usually not compatible (Wallmo 1981).

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Population

Population Trend

Major Threats

Comments: Overgrazing by cattle may degrade habitat (see ES files).

Conservation Actions

Management Requirements: Cattle grazing results in loss of hiding cover for fawns, possibly may increase rate of loss of fawns to predation (Loft et al. 1987). On summer range in the Sierra Nevada in California, cattle evidently competed with deer, particularly at high stocking rates and during a year of below-average precipitation; adverse effects could be reduced by reducing or eliminating cattle grazing during early summer on all or part of a grazing allotment (Kie 1991; see also Loft et al. 1991 for further evidence of cattle-induced habitat shifts by mule deer).

See Wood and Wolfe (1988) for discussion of viability of intercept feeding to reduce deer-vehicle collisions.

See Andelt et al. (1991) for information on the relative effectiveness of various repellents for reducing damage to plants (when the deer were moderately hungry, even the best repellents failed to deter browsing).

Douglas fir and Ponderosa pine are of major economic importance for commercial timber. However, these trees are browsed heavily by O. hemionus. Browsing of other trees is seldom considered an economic problem. In the Douglas fir region, O. hemionus browses on trees during both the dormant and growing seasons. Practices that encourage the growth of O. hemionus populations can therefore also encourage damage. Douglas fir is harvested mainly by clearcutting and is regenerated by planting with nursery-grown stock. O. hemionus is attracted to clear-cuts, and Douglas fir is an acceptable and sometimes preferred forage species. This situation invites browsing of sufficient intensity to influence forest regeneration in many areas (Wallmo 1981).

Odocoileus hemionus is of tremendous interest to hunters. Populations of O. hemionus that are large enough to support hunting during two or three weeks in autumn offer countless recreational opportunities for the public. This desire to hunt generates revenue for the economy (Wallmo 1981).

Comments: Browsing on juvenile fruit trees in northern Utah had no effect on tree growth or initial fruit production (Great Basin Nat. 52:352).

Comments: See Cronin (1991) for information on the restricted gene flow that occurs among extant populations of white-tailed deer (O. virginianus), mule deer (O. h. hemionus), and black-tailed deer (O. h. columbianus and O. h. sitkensis); there is a low level of introgressive hybridization of mtDNA from mule deer and black-tailed deer into white-tailed deer populations in a few areas in western North America. MtDNA and serum albumin data indicate that gene flow between white-tailed deer and mule deer in Montana is not extensive (Cronin et al. 1988). See Hughes and Carr (1993, Can. J. Zool. 71:524-530) for information on hybridization between white-tailed and mule deer in western Canada.

In most areas of sympatry between O. virginianus and O. hemionus in the southwestern U.S., there is little evidence of nuclear gene introgression, though electrophoretic data do indicate hybridization in some localities (Derr 1991). Carr and Hughes (1993) documented recent mtDNA gene flow between mule deer and white-tailed deer in western Texas. Carr and Hughes (1993) found that some populations of mule deer are genetically more closely related to white-tailed deer than to other populations of mule deer; see Carr and Hughes for possible interpretations.

See Cronin et al. (1991) for information on genetic differentiation among subpopulations of mule deer. Cronin (1992) found considerable intraspecific variation in mtDNA in O. hemionus; different subspecies (mule deer and black-tailed deer) had distinct genotypes. Mule deer and black-tailed deer interbreed to a limited extent in a zone along the Cascade Range. Cronin (1991) found evidence of considerable interbreeding of mule deer and black-tailed deer in a contact zone in British Columbia.

This species was included in the genus Dama by Hall (1981), in Odocoileus by Jones et al. (1992), Baker et al. (2003), and Grubb (in Wilson and Reeder 1993, 2005).

See Cronin (1991) for a phylogeny of the Cervidae based on mitochondrial-DNA data. See Kraus and Miyamoto (1991) for a phylogenetic analysis of pecoran ruminants (Cervidae, Bovidae, Moschidae, Antilocapridae, and Giraffidae) based on mitochondrial DNA data.