The mule deer gets its name from its overly large ears. In its scientific classification, Odocoileus hemionus, the species name is Latin for “half-mule.” The white-tailed deer is Odocoileus virginianus — the later part of that title referring to when the species was once known as the “Virginia deer.” If mule deer get their common name from up front, whitetails get theirs from the other end. However, the majority of the time you see more white on the tail end of a mule deer, which has a very large patch of white, only partly covered by a rope-like, white tail with a black tip. Whether the tail is up or down, you can always see plenty of white on the rump of a mule deer. A whitetail, on the other hand, normally covers most of its narrow white patch with a thick, dark tail but raises its tail to alert, or flag, others of danger. To make it an effective defense mechanism, the difference between “calm” and “freaked out” has to be as big as possible.
While it’s hard to determine size and weight in the field, in Colorado, mule deer tend to be a bit bigger and weigh in a little heavier than white-tailed deer. Age, nutrition and other environmental factors play big roles in a specific deer’s height and weight. Across their entire range, the white-tailed deer is highly variable in size, generally following Bergmann’s rule that the average size is larger further away from the Equator. Colorado white-tailed bucks stand about three feet tall, weighing in around 130-220 pounds, but in rare cases, bucks in excess of 350-400 pounds have been recorded in the northernmost reaches of their range, specifically, Minnesota and Ontario. The mule deer stands three to three and a half feet tall at the shoulder, with bucks weighing 125-250 pounds. The heftiest, trophy-sized mule deer buck can weigh more than 450 pounds.
Bucks of both species shed their antlers yearly — in January or February for whitetails, while mule deer have to hold up their racks a month longer, typically shedding them in February or March. Fully formed, mature mule deer racks are taller and broader than those on whitetails. They are also bifurcated, forking in two directions as they grow, splitting again to create more tines (points), and so forth. A white-tailed deer buck’s antler points will all grow off of one main beam. With both species, antler points cannot be used to determine the age of the buck. However, with proper nutrition, older bucks generally have larger antlers with more points than do younger deer.
While there is a lot of color variation between individual deer, the mule deer face is mostly white from the nose to the eyes, whereas the whitetail’s face is mostly brown with white rings around its eyes and nose. Both have a white patch on their throats. Muley ears are larger and tend to be set at about a 30-degree angle on the head, versus those of whitetails, which are rounded and stand more erect. Deer have dichromatic (two-color) vision with blue and yellow primaries. Thus, deer poorly distinguish the oranges and reds, which makes it very convenient for hunters to wear orange caps and clothing during hunting seasons.
Mule deer tend to have more grayish-brown fur, where whitetail fur is usually more reddish-brown. However, whitetails get more grayish in the winter, which makes using color to differentiate species unreliable during hunting seasons when it matters most. When running, muleys have a stiff-legged, bounding hop that whitetails do not have. White-tailed deer gallop rather than hop.
Mule deer does weigh in between 100 and 220 pounds, whereas white-tailed does come in anywhere from 90-200 lbs. Whitetails also have a higher birth rate, their does can often breed their first fall at 6 months of age. Mule deer does take longer to mature. Mule deer mate from mid- to late-November; white-tailed deer breed from late-November to early December. Gestation for mule deer is seven months, versus six and a half for white-tailed deer.
Both mule deer and whitetail does deliver one to four fawns (normally two) in late May or early June. A doe will usually produce a single fawn the first year she gives birth and then produce twins in following years. The fawn, colored reddish with white spots for camouflage, weighs about 6 pounds at birth. It must nurse within the first hour and stand within the first 12 hours. During early weeks of life, the fawn sees its mother only at mealtimes for feeding. Spots begin to fade by the end of the first month. Fawns usually stay with the doe for the first full year.
Photos by © Wayne D. Lewis/CPW