Mule deer: A common sight in Colorado

If you live in Eagle County and have not seen a mule deer, you are not paying attention! They are everywhere. You can tell when a person driving through Wildridge is not from Colorado. They are the ones who slow down or stop to view the deer.

Mule deer (Odocoileus hemionus) are found throughout western North America and are generally found west of the Missouri River. Black-tailed deer are considered a subspecies.

A relative, the white-tailed deer (Odocoileus virginianus), is generally found east of the Rocky Mountains. There are white-tails in the foothills of Colorado and the Rockies of the northern United States and are often seen near the Air Force Academy and along the Platte and Poudre Rivers on the plains.

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Mule deer get their name from their large mule-like ears. Males (bucks) can be 40-plus inches at the shoulder and weigh 300-plus pounds. Females (does) are generally smaller, as are white-tailed deer. The tail of mule deer are narrow and black tipped. White-tailed deer have broader tails and the underside is pure white.

Another significant difference between the two has to do with the shape of the antlers. Mule deer antlers split or fork as they grow. The main beam splits into two and each of those forks split into two, a shape called bifurcation. White-tails have a single beam and each tine grows up from it.

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Even though mule deer are the most common deer in Colorado, the deer crossing signs on the highways depict white-tailed deer. The antlers and the shape and position of the tail are characteristic of white-tailed deer.

Antlers, which grow only on males, are shed every year, usually early spring, and a new set immediately begins growing. Antlers are made from bone while horns are more like finger nails. Horns, which may be found on males and females, are kept for the life. (The exception is the pronghorn antelope, which shed their horns each year.) Antlers grow from a skull bump called the pedicle and amazingly reach full size by mid-summer.

As antlers grow, they are covered with skin and fur called velvet. Velvet is rich with blood vessels, which help with rapid growth. When the blood supply stops in the fall, the buck rubs the skin off on trees and brush, perhaps because it itches. Antlers are used by the males during the fall rut to establish dominance both by appearance and fighting.

Mule deer tend to live in woodlands and feed on woody vegetation, leaves and some grass. Gardens are often hit hard by deer. They compete little with elk, which tend to eat grasses and forbs. During hard winters some people want to start feeding programs. That can kill the animals because deer may not be able to digest food they don’t regularly consume. Many varieties of protozoa and bacteria help break down food in their stomachs. Without specific organisms, deer cannot digest food such as hay and corn and may starve with a full stomach.

Females go into estrus in the fall rut. After six to seven months, fawns are born, and twins are very common. The fawns have white spots that help them conceal themselves under bushes. The spots disappear in the fall as the winter coat begins to develop.

Mountain lions are local predators of mule deer. Wolves are also in the mix in the Northern Rockies. Bears, coyotes and other predators may take down fawns or sickly adults.

One interesting thing many observe with mule deer is a maneuver they use to escape a threat. It is called pronking. All four legs hit the ground at the same time, and they bounce away as if there are springs on their hooves. It is amazing how quiet this maneuver is.

When mule deer are spotted near the road, drivers should use caution. Deer may unexpectedly dart onto the road. Drivers often miss the first deer and hit the second that follows. Passengers are more often injured by accidents from erratic maneuvers to avoid the deer than hitting the animal. Use caution!

Rick Spitzer is the author of “Colorado Mountain Passes,” available at The Bookworm of Edwards, City Market and on Amazon. The book provides photos and text about the history, lore, wildlife and scenery around the passes of Colorado.