Rocky Mountain Bighorn Sheep Ovis canadensis canadensis
The Rocky Mountain Bighorn
The Rocky Mountain Bighorn Sheep is the largest wild sheep inhabiting North America. A large ram may weigh over 300 pounds and stand over 42 inches tall at the shoulder. They are generally a dark brown to gray/brown color with a white rump patch, muzzle, and back of legs. Their coats may appear considerably lighter in spring before the winter coat is shed revealing the darker summer coat beneath. Rams have horns that are massive and tightly curled close to the face. Ewes have smaller, shorter horns that curve only slightly. Ewes typically weigh 125-150 pounds. In the wild, they typically live 6-15 years.
About 750,000 years ago, the ancestors of the Rocky Mountain bighorn sheep crossed the Bering Land Bridge from Siberia into Alaska. From there, they spread throughout the West, finding homes in rocky terrain from Canada down to northern Mexico. Bighorn sheep populations peaked in the millions, and they were an important resource for indigenous peoples all along the mountainous spine of the Rockies. The sheep provided meat, clothing, and tools, and held different mythologic and symbolic meanings for various tribes. Petroglyphs featuring bighorns are among the most common historic images across the western U.S.
Fighting for dominance or mating rights during the rut, which occurs between October and January, males face each other, rear up on their hind legs, and hurl themselves at each other in charges of nearly 20 miles an hour. The resounding crash of horns can be heard echoing through the mountains as the confrontation is repeated — sometimes for many hours — until one ram submits and walks away. The animal’s thick, bony skull usually prevents serious injury.
All wild sheep, including Rocky Mountain bighorns, live in social groups, but rams and ewes typically meet only to mate. Rams live in bachelor groups and females live in herds with other females and their young. When fall mating arrives, rams gather in larger groups and ram fighting escalates; usually, only stronger, more dominant rams are able to mate. In winter, bighorn herds move to lower-elevation mountain pastures. In all seasons, these animals eat available grass, seeds, and plants. They regurgitate their food to chew it as cud before swallowing it for final digestion.
Lambs are born each spring on high, secluded ledges protected from bighorn predators such as wolves, coyotes, and mountain lions — though not the golden eagle, which targets lambs. Still, in areas where predator control is not a priority, bighorn numbers can be adversely affected by big cats and wolves. The young can walk soon after birth, and at one week old each lamb and its mother join others in a herd. Lambs are playful and independent, though their mothers nurse them occasionally for up to six months.
Rocky Mountain Bighorn Sheep Demographics
Two hundred years ago more than 200,000 bighorn sheep lived throughout the western United States, Canada, and northern Mexico. A dramatic drop in the overall population occurred from 1870-1950, crashing bighorn numbers to just a few thousand. Unregulated hunting, habitat destruction, overgrazing of rangelands, and diseases contracted from domestic livestock all contributed to the decline. Thanks to the creation of the North American Model of Wildlife Conservation and the work done by various sportsman’s groups over the past century (including transplant programs,) bighorn sheep populations today are doing well.
It is estimated that today there are about 70,000 bighorn sheep living in North America. However, much of their historical range no longer support bighorn populations, and interstate highways have cut off once-connected mountain ranges. Modern threats include habitat loss (primarily from housing development), water loss caused by human diversion or livestock use and recent severe drought conditions, mining, vehicle collisions, and human encroachment into remote bighorn habitats via OHVs, mountain bikes, and hiking. Together, these factors continue to seriously threaten bighorn populations. In fact, bighorns are very sensitive to changes in the environment and are often referred to as an “indicator species,” meaning that a healthy, thriving herd of bighorns is indicative of a healthy, thriving ecosystem. It is estimated that bighorn populations today stand at only about 10 percent of historic numbers.
Rocky Mountain Bighorn sheep are found in British Columbia and Alberta, Canada, and in the western United States south to New Mexico. All state and Canadian provincial governments jealously protect their bighorn populations by severely restricting the number of available hunting permits to a handful each year, with the vast majority of tags issued either through the state’s tag draw system and/or monitoring harvest during the season in the case of hunting that occurs in the very few open areas. A few tags are sold by various conservation organizations at auction each year for big money, with the funds put back into sheep conservation efforts. In most states, drawing a Rocky Mountain bighorn tag is a “once in a lifetime” tag. Hunters might accumulate bonus or preference points for several decades before even having a chance to draw the most coveted of all North American big game hunting tags.
- A bighorn sheep ram’s horns can weigh 30 pounds — more than all the bones in his body combined. Females (ewes) also have horns, but they are of smaller size.
- The hooves of the bighorn sheep have a hard outside rim used for digging into the ground or cutting into snow or ice. The inside of the hoof is soft and spongy like the bottom of a tennis shoe to aid in traction. They have split hooves that pinch and hold rocks somewhat like clothespins and the claws higher up on the foot act like brakes if the sheep starts to slide on loose rock or slippery surfaces. Thanks to their amazing balance, bighorn sheep can stand on ledges that are only 2 inches wide. They can also jump 20 feet, climb up a mountain at a brisk 15 mph, and run up to 30 mph on flatter ground.