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From September to mid-November Colorado’s meadows, valleys, and woodlands become staging grounds for an array of sights and sounds associated with courtship behaviors. As aspen trees transition to autumn colors, mule deer, white-tailed deer, and the American elk, or Wapiti, begin their annual breeding season or 'rut'. Prior to the rut, from approximately March to September, mature males invest a great deal of energy growing antlers from bony projections on their skulls. During this growth period, antlers are covered with finely haired skin called velvet that includes a network of tiny, nutrient-carrying blood vessels. At the end of the growth cycle, antlers are rubbed against trees and other vegetation to remove the velvet. Following the rut, in mid- to late winter, antlers are shed and the process begins anew.

Why devote so much time and effort to growing something that is only temporary? It’s nature’s way of ensuring that the fittest animals breed and pass along their genetic traits. The strongest mature males usually grow the biggest 'racks', which is a distinct advantage in male-to-male combats over territory. These sparring encounters normally do not cause permanent injury or death, but only the victorious males will gain access to a harem of breeding females. Even then, the victor may have to continually defend his harem against other male challengers.

The rut presents a perfect opportunity to watch and learn how these Colorado mammals orchestrate one of nature’s grandest spectacles. During your observation, be aware of the animals’ response to your presence and don’t approach too closely. If they begin moving away from you—you're too close! Always use binoculars or spotting scope to maintain a safe distance and avoid interfering in the process.

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The American elk is distinguishable from mule and white-tailed deer by its much larger size and the dark mane on its neck, with contrasting paler body. Male elk, or bulls, have single beam antlers that extend backward over the neck and shoulders—the antlers may weigh as much as 40 pounds! As bulls compete for females they will lay claim to territory by a loud, almost musical sound called bugling. Other behaviors by males during the rut include thrashing, digging, wallowing, and posturing. In Colorado, the elk rut is usually concluded by late October.

Much like mule deer, elk move down slope during the winter to forage in areas with less snow cover. Large elk herds can often adversely affect stands of aspen by browsing on seedlings, twigs, and bark. You can identify chewed aspen bark by the dark scarring (old browse), or lighter fresh tooth scrapes at heights of three to six feet.

Where to Look

If you don’t want to compete with the elk-viewing crowds at Rocky Mountain National Park, try the Dowd Junction Elk Viewing Area (site number 113 in the Colorado Wildlife Viewing Guide, Second Edition) three miles north of Minturn on State Highway 34. This area serves as a wintering range for several hundred elk. If you want to incorporate a hike to observe elk, consider Mueller State Park (site number 74), just south of Divide on State Highway 67. 

(The viewing guide is available at many bookstores, through our online store, or through the Colorado Wildlife Heritage Foundation.)

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Although mule deer occupy a wide range of habitats in Colorado, they generally move from higher slopes to lower elevations during the winter. Periods of daily activity are dependent on locale, weather, forage, and human presence but, in general, mule deer are nocturnal and crepuscular (active at dawn and dusk.) As winter approaches, they will become more diurnal (active during the daylight hours). Mule deer are recognizable by their large, conspicuous ears, contrasting pale muzzle, and grayish forehead. Antlers on mature bucks (males) branch equally and project forward and upward from their attachment points on the skull.

Where to Look

Opportunities to see mule deer abound in Colorado. West of Trinidad near the town of Weston, mule deer and elk are abundant in the Bosque Del Oso State Wildlife Area (site number 88 in the viewing guide). East of Grand Junction on the Grand Mesa check out the Crag Crest Trail (site number 186) on State Highway 65 for bugling elk and mule deer in the fall.

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Colorado's white-tailed deer typically locate in riparian woodlands and associated irrigated agricultural lands of the eastern plains. Whitetails have smaller ears and less facial color contrasts (except for the white band around the nose) compared to mule deer, and have, of course, the characteristic bushy, white tail that stands erect when they run. The peak of the rut for this species is early November. Look for scrapes on the ground where bucks have left their scent to mark territory. Whitetail males have antlers with a well-defined single beam from which individual, non-branching tines (points) project. Unlike mule deer, whitetails do not migrate seasonally.

Where to Look

White-tailed deer are often difficult to find because they do not remain in open areas for very long. They are active mostly during the twilight hours of dawn and dusk. To view white-tailed and mule deer near Denver, visit the Rocky Mountain Arsenal National Wildlife Refuge (site 62 in the viewing guide). In the southeastern part of the state, south of Lamar near Springfield, try Two Buttes State Wildlife Area (site 25) for some excellent deer viewing opportunities.