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Get Wild: Rocky Mountain bighorn sheep, a Colorado treasure

Frances Hartogh
Get Wild
Rocky Mountain bighorn sheep are one of two bighorn species in Colorado, but Rocky Mountain bighorn sheep are the only native species in the state.
Colorado Parks and Wildlife/Courtesy photo

On May 1, 1961, Colorado designated the Rocky Mountain bighorn sheep as our state animal. What a great choice! Native to Colorado, Ovis canadensis, with their incredible coiled horns and superb climbing ability, are found only in the Rockies. Muscular and stocky, measuring up to 6 feet long and 250 pounds, Rocky Mountain bighorns are nevertheless agile rock climbers. Their two-toed hooves have padded bottoms for added traction, and their toes spread apart for extra stability.

Two bighorn species live in Colorado, but only our Rocky Mountain bighorn is native. Desert bighorns were introduced near the Colorado National Monument in 1979.

More about those truly big horns — a male ram’s horns can weigh up to 30 pounds. Thickly ridged with growth rings, which can tell a sheep’s age, horns aren’t shed. Ram’s horns reach “full curl” around 7-8 years. Females, called ewes, have slender, spiky horns that don’t make a full curl.



What do rams do with those magnificent horns? They have butting battles! When fall comes, rams have head-butting contests to establish dominance. Running at each other at speeds up to 20 mph, they ram heads. The sound can travel a mile. Battles can last up to 20 hours. How do they survive these crashes? Their double-layered skulls are honeycombed with bone struts, while thick tendons link spine and skull to help recoil from the impact.

Highly social, Rocky Mountain bighorns usually separate into two groups — mature rams in one, and ewes, lambs, and immature rams in another. These groups join during the November through December rut and sometimes for shorter periods in spring. In late April to early June, ewes give birth usually to one lamb, high in rocky cliffs that allow protection from predators.



Year round, bighorns need territory with two important things: good grazing and access to rocky terrain providing escape routes. In summer, bighorns graze in high alpine tundra, meadows, and open woodlands, eating various grasses, shrubs, clover, phlox, and cinquefoil, with nearby cliffs providing protection.

In winter, bighorns descend to open south-facing slopes with rocky outcrops and cliffs, where low snow allows grazing, and cliffs provide safe haven from predators. Our local Gore/Eagles Nest bighorn herd’s winter habitat in East Vail, with its open south-facing slopes topped by rocky outcrops, is ideal. This habitat has featured prominently in recent news due to Vail Resorts’ plans to construct employee housing there. If development occurs there, Colorado Parks and Wildlife says that the herd “simply won’t exist.” Check out this video that includes some amazing footage of our local bighorns.

Bighorn predators include coyotes, mountain lions, and even eagles. Slower than elk and deer that use both speed and agility to evade predators, bighorns depend on their amazing climbing and balancing ability to avoid attack. However, perhaps the biggest threats to bighorns are loss of habitat to human development, pneumonia contracted from domestic sheep, and competition from non-native species like mountain goats that also carry pneumonia pathogens lethal to bighorns. As a result, efforts are underway in bighorn habitat to “retire” domestic sheep-grazing permits and control mountain goat populations.

By the early 1900’s, Rocky Mountain bighorn populations had dwindled due to unregulated hunting and diseases introduced through European livestock. In the 1940’s, Colorado Parks and Wildlife began conducting bighorn transplants, including between Georgetown and Silver Plume. The well-known “Georgetown Herd” is one of the largest in Colorado. 

What makes our neighboring Gore/Eagles Nest bighorn herd extra special is that it may be the last truly native herd in our state. This herd has used its winter range in East Vail since before humans ever occupied the valley. 

Frances Hartogh
Frances Hartogh/Courtesy photo

“Get Wild” publishes on Fridays in the Summit Daily News. Frances Hartogh is a volunteer wilderness ranger and sawyer for the Eagle Summit Wilderness Alliance, an all-volunteer nonprofit that helps the U.S. Forest Service protect and preserve the wilderness areas in Eagle and Summit counties. For more information, visit EagleSummitWilderness.org.


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