Large-eared deer, family Cervidae (order Artiodactyla), found in western North America from Alaska to Mexico. A valued game animal, prized for its flesh, hide, and antlers, the mule deer lives alone or in small groups, sometimes gathering in larger herds in winter, in rough, mountainous terrain, and also in desert regions. The mule deer is migratory; it seeks lower altitudes during the winter months and returns to its summer pastures long after the snow has melted.

The mule deer is stockier than the related white-tailed deer (O. virginianus). It stands 90-105 cm (3-3.5 feet) at the shoulder and is yellowish to reddish brown in summer, grayish brown in winter. The tail is white with a black tip, except in the black-tailed deer (O. hemionus columbianus), a subspecies of the Pacific Northwest in which the tail is black on the entire upper surface. The male has antlers that fork twice above a short tine near the base; a mature male normally bears five tines on each antler.

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