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Mammal Species of the World's Boreal Forests

BIRDS

   
Odocoileus hemionus
Mule Deer

Description

Distinguishing Features - The pelage 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. 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 the species, but remain constant throughout the life of an individual. Mule deer possess a dark V-shaped mark, extending from a point between the eyes upward and laterally. This mark is more conspicuous in males. Mature males, in general, exceed females in weight and stature. Weight ranges from 45 to 150 kg in males, and 43 to 75 kg in females. Body length ranges from 126 to 168 cm in males, and 125 to 156 cm in females. Shoulder height ranges from 84 to 106 cm in males, and 80 to 100 cm in females.

Mule Deer Habitat

The Mule deer is remarkably adaptable and widespread throughout western portions of Canada and the United States, in open coniferous forests, grasslands and river valleys.

Diet

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. Because nutritious forage is in poor supply for much of the year, the species has an annual cycle of metabolic rates. A higher energy flux and food intake in the summer enables mule deer to capitalize on abundant high-quality forage for growth and fat storage. A lower energy flux in the winter permits it to survive on a lower intake of poor-quality forage while minimizing the catabolism of stored fat for body functions. In adult males, food intake drops abruptly with the onset of rut

Mule deer frequently browse leaves and twigs of trees and shrubs. Green leaves are very succulent and 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. They also eat acorns, legume seeds, mushrooms, and fleshy fruits, including berries and drupes, that have moderate cell-wall levels and are easily digested.

Notes

Individuals of the species tend to confine their daily movements to discrete home ranges. Most mule deer with established home ranges use the same winter and summer home ranges in consecutive years. Dispersal involves movements beyond the home range to distances of up to 8 km. This movement results in the establishment of a new home range. Seasonal movements involving migrations from higher elevations (summer ranges) to lower winter ranges are associated, in part, with decreasing temperatures, severe snowstorms, and snow depths that reduce mobility and food supply. Deep snows ultimately limit useable range to a fraction of the total.

The mule deer has several distinct strategies for avoiding predators. It specializes in detecting danger at a very long range by means of large ears and excellent vision. Once danger is detected, mule deer may choose to hide, or move into cover and cautiously outmaneuver the predator. Another strategy is to depart while the predator is still a long way off and move away to another area. It is also an excellent swimmer, but water is rarely used as a means of escaping predators.

The Sitka black-tailed deer Odocoileus hemionus sitkensis is native to the wet coastal rain forests of Southeast Alaska and north-coastal British Columbia but its range has been expanded by transplants. Deer populations in Alaska are dynamic and fluctuate considerably with the severity of the winters.

The Sitka black-tailed deer is smaller, stockier, and has a shorter face than other members of the black-tailed group. The summer coat of reddish-brown is replaced by dark brownish gray in winter. Antlers are dark brown with typical black-tailed branching and are relatively small.



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