The mule deer gets its name from its large mule-like ears. It is the common deer of western mountains, forests, deserts and brushland. The major predators of mule deer are wolves, mountain lions, and coyotes;bobcats often take fawns.
Mule deer are most active in the morning and evening, spending most of the daylight hours bedded down under cover where they are hidden from predators. Only males (called bucks) have antlers, which are typically shed in January. A new set of antlers is grown every year, with the new growth beginning in spring. As the antlers grow, they are covered with velvet, a layer of skin rich with blood vessels and nerves that nourish the bony antlers. In late summer, as the daylight hours gradually decrease, hormonal changes in the buck causes the antlers to harden and the blood supply shuts off. The velvet becomes dry and is eventually rubbed off, leaving only the bony antler. During the rut, or mating season, bucks establish dominance by using their antlers in sparring competitions. The most dominant bucks tend to breed with more females. Mule deer occur in a wide variety of habitats throughout their range and are adapted to feeding on a wide range of plant material. They can be found living in the high mountains, the foothills, the plains, and even the deserts of the Western United States. The temperate rainforests along the Pacific coast are home to the black-tailed deer, a distinct form of Odocoileus hemionus.
Mule deer are a very important game species and their population ecology, management and conservation has been extensively researched over the past 100 years.