The two most widespread deer species across North America are the white-tailed deer (Odocoileus virginianus) and the mule deer (Odocoileus hemionus). Although both are members of the same genus and share general body forms, they have evolved distinct physical and behavioral adaptations suited to their respective environments. Recognizing the differences between these similar-looking animals requires attention to specific features, which are often the clearest indicators of the species.
Identifying by Ears and Antlers
The size of the ears is the most apparent difference, giving the mule deer its common name. Mule deer possess noticeably oversized, prominent ears that may measure up to three-quarters the length of their head. White-tailed deer, conversely, have smaller, more rounded ears that appear proportionate to their head size.
Differences in antler structure provide a definitive way to distinguish the males of each species. The antlers of a mature white-tailed deer grow from a single main beam, with individual tines projecting upwards. Mule deer antlers, however, typically exhibit dichotomous branching; the main beam splits into two forks, which can split again. Furthermore, the mule deer often has a distinct dark gray patch on its forehead and muzzle, while the white-tail’s face tends to be cleaner with lighter markings.
Identifying by Tail and Body Shape
The tail is perhaps the most famous visual distinction and the source of the white-tailed deer’s name. The white-tail has a broad, long tail that is brown on the top surface, but lined with bright white hair underneath. When alarmed, the white-tail raises, or “flags,” this tail, exposing the bright white underside to signal danger as it flees.
In contrast, the mule deer has a narrower, rope-like tail that is generally white with a distinctive black tip. This tail is typically held low and close to the rump when running, unlike the raised white-tail flag. Mule deer are stockier and heavier, with a more robust body build and a deeper chest. White-tailed deer appear more slender and graceful, possessing relatively longer legs suited for navigating dense cover.
Geographic Range and Movement Patterns
The preferred habitat of each species largely dictates its geographic distribution. White-tailed deer are highly adaptable and are found across nearly all of the continental United States and Canada, thriving in forests, river bottoms, and agricultural areas east of the Rocky Mountains. Mule deer are primarily animals of the rugged, open country and mountainous terrain of the Western United States and Canada.
The differing terrains have led to a unique divergence in their movement when fleeing. A white-tailed deer runs swiftly, using a smooth, fluid, galloping gait that allows for quick bursts of speed and maneuvering through dense cover. Mule deer, adapted to uneven, rocky ground, often employ a distinctive bounding motion called stotting or pronking. In this gait, all four feet push off the ground and land simultaneously.