Rocky Mountain Bighorn Society

By Christopher Roe, Certified Wildlife Biologist

Bighorn sheep are arguably one of the most recognizable hoofed animals in the western United States, if not in all of North America. Consisting of several races, or varieties, bighorn sheep are distinguished from their northern cousins (thinhorned sheep) by their heavier, blockier bodies, and more massive horns, which often have broken or "broomed" tips. Heavily ridged and massive horns curling back, downward, and up into the classic "full curl" make the mature bighorn ram truly a sight to behold.

Adult bighorn sheep typically weigh between 110 and 275 pounds (50-125 kg) and are approximately 30 to 44 inches (75-110 cm) tall at the shoulder, depending on the sex and age of the animal. Hair coat usually ranges from a dusty tan in summer to dark brown or chocolate in winter. The characteristic white or gray rump patch remains throughout the year. Horns of rams are significantly larger than ewes, even at an early age. Rams develop significant horn mass within the first several years, and obtain most of their horn growth within their first 7-8 years. After 7-8 years, horn growth slows with the brooming of horn tips becoming increasingly noticeable as the years progress.

Although sexually mature at a young age, ewes typically do not bear young until 2-3 years of age and rams (especially in populations with many mature rams) typically do not breed until they are much older. Breeding occurs in late autumn with ewes giving birth to a single lamb in early to mid summer. Twin lambs are uncommon.

Bighorn sheep are gregarious, social animals that typically show high fidelity to their chosen home range. Throughout much of the year, mature rams typically separate themselves from groups of ewes and lambs, and from bands of immature rams. Only during the breeding season, and on some winter ranges, do you find a mix of sexes and age classes for prolonged periods.

Bighorn sheep are active throughout the day, with several periods of foraging interspersed with periods of grooming, sleeping, and/or playing (often ewes with young lambs and lambs with one another). Although typically associated with rough, rocky, open terrain, bighorn sheep can be found on alpine slopes above tree line to the shrub and timber covered canyon lands of lower elevations.

Several varieties, or races, of bighorn sheep can be found in western North America. Rocky Mountain bighorns (Ovis canadensis canadensis) can be found throughout the Rocky Mountains; from Canada to southern New Mexico, from the western Dakotas to parts of Washington and Oregon. Desert bighorns (of which there are four separate varieties, Ovis canadensis nelsonii, O. c. mexicana, O. c. weemsi, and O. c. cremnobates) can be found throughout the desert southwest of the United States in portions of Colorado, New Mexico, Arizona, Utah, Nevada, and California, and in northwestern portions Mexico. Another separation in bighorn sheep has been made in the case of the California bighorn (Ovis canadensis californiana), although this classification has been contested in recent years. Regardless of their classification, these animals have a range similar to Desert bighorns, which include a few small areas in the states of Oregon and Washington.