They are closely related to the Rocky Mountain subspecies, which inhabits mountainous wooded areas. Their hide is rusty brown in the summer, and gray in winter, with white undersides year-round.
Bucks grow a new set of antlers each year, which they shed after the breeding season.
Mature bucks have antlers that branch equally, with each antler having two main beams, and two or more tines per beam. Classified as herbivores, mule deer browse on grasses, green plants, twigs, bark, buds, fruit, and nuts. Their lifespan is approximately ten years. Predators such as mountain lion and coyote may feed on mule deer. Stotting allows the deer to cover significant distances with minimal effort and clear large obstacles that can impede their predators.