Figure 2. Morphological differences between mule and white-tailed deer.
Desert mule deer are generally smaller and lighter in color than the Rocky Mountain subspecies of mule deer located farther north. Likewise, their antlers are not as massive as those of the Rocky Mountain subspecies. Mule deer can be distinguished from white-tailed deer by differences in antler characteristics, size of ears, appearance of tail and the size of the metatarsal gland (Fig 2). When frightened, mule deer tend to escape in bounding leaps, as opposed to the whitetail’s more traditional running gait. Mule deer tend to run with tails held down, whereas white tails hold their (“flags”) up when flushed.
Mule deer become reproductive at about 2 years of age and attain maximum body size at about age 6. A mature buck can weigh up to 200 pounds on the hoof, whereas a mature doe may weigh up to 120 pounds. Typical field-dressed weights in the Trans-Pecos area range from 100 to 130 pounds for bucks and from 60 to 80 pounds for does (Fig.3). Weights may be somewhat larger in the Panhandle area as a result of better forage availability (winter wheat, alfalfa).
In captivity mule deer may live as long as 15 to 20 years, but few wild deer live more than 8 years. Bucks attain maximum antler development at 5 to 7 years of age. Antler size is influenced by age, level of nutrition and to a lesser degree, genetics. A diet consisting of 16 percent crude protein is recommended for maximum antler development and reproductive performance.
Does generally breed at age 2 and yearlings may breed if in excellent condition. The breeding season or rut extends from mid-November through mid-February, with December being the peak. The gestation period is about 7 months (210 days), with most births occurring in July and August. Does generally give birth to single fawns the first time they breed, but twins are common thereafter if forage conditions are adequate. Fawn crops generally average about 45 percent, depending primarily on seasonal weather conditions, forage availability and predation. Mule deer may have somewhat lower reproductive potential (lower fawn crops, fewer twin fawns, fewer yearling does breeding) than white-tailed deer. However, this may be related more to the environment than to the species’ characteristics. In areas with both white-tailed and mule deer, productivity is similar.