The state of Colorado, with its diverse geography, is home to two species of the genus Odocoileus, commonly known as deer. These large herbivores are an important part of the state’s ecosystem. Understanding the differences between these two species is key for anyone interested in wildlife viewing across Colorado’s varied landscapes.
The Mule Deer
The Mule Deer (Odocoileus hemionus) is the more widely distributed and iconic deer species across Colorado’s western and mountainous regions. Their common name comes from their most distinguishing feature: their ears, which are disproportionately large, resembling those of a mule. Males, or bucks, develop antlers that are characterized by a bifurcated structure, meaning each tine forks as it grows, creating a series of symmetrical branches rather than growing from a single main beam.
The Mule Deer’s gait is unique when they are moving quickly or alarmed. They employ a bounding motion called “stotting,” where all four feet push off the ground simultaneously. Their tail is relatively small and rope-like, white with a distinctive black tip. Mature bucks can be quite large, with some exceeding 300 pounds, while does are noticeably smaller.
These deer are highly adaptable browsers, preferring a diet of woody vegetation, shrubs, and forbs. They thrive in “edge” habitats, which include the foothills, shrublands, pinyon-juniper forests, and high-elevation mountain meadows. Many Mule Deer herds are migratory, moving from high-altitude summer ranges down to lower-elevation winter ranges to find accessible forage when snow is deep. This vertical migration pattern contributes to their widespread presence across the state’s rugged terrain.
The White-tailed Deer
The White-tailed Deer (Odocoileus virginianus) is the second species found in Colorado, generally favoring lower elevations. A key physical trait that gives this species its name is its broad, brown tail, which has a bright white underside. When startled, the deer raises this tail like a flag, revealing the white flash as it runs with a graceful, long-strided lope.
White-tail bucks have a different antler configuration. Their tines all grow upward from a single, forward-curving main beam, without the distinct branching or forking. The ears of the White-tailed Deer are also visibly smaller and less prominent than the large ears of the Mule Deer. While White-tailed Deer are generally smaller than Mule Deer, large bucks can still reach weights over 300 pounds.
These deer primarily inhabit riparian zones, stream-side woodlands, and agricultural fields where thick cover is readily available. They are less reliant on mountainous terrain and do not typically engage in the long-distance vertical migrations common to Mule Deer. Their preferred habitat near water sources and farmlands reflects their tendency to stay within a relatively small home range, often a square mile or less.
Regional Distribution Across Colorado
The geographic distribution of the two deer species across Colorado largely follows the state’s major ecological divisions. Mule Deer are dominant throughout the mountainous Western Slope and the high-elevation areas of the Front Range. Readers exploring national forests or higher foothills will almost exclusively encounter the Mule Deer.
White-tailed Deer populations are concentrated mainly along the Eastern Plains, particularly in the river bottoms and along corridors like the South Platte River. These areas provide the dense cover and rich forage of riparian habitat that the species prefers. While a few smaller populations exist on the Western Slope, the vast majority of White-tails are found in the eastern third of the state and in urban fringe areas. This distinct separation means that a sighting of a deer in the open fields of eastern Colorado is more likely to be a White-tail, while a mountain encounter points toward a Mule Deer.