Colorado DOW Transplants Bighorn Sheep on Western Slope

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In an effort to improve long-term survival of desert bighorn sheep in western Colorado, the Colorado Division of Wildlife has moved 15 of the majestic animals into prime bighorn habitat in the Middle Dolores River canyon.

Twenty years ago, the Division established a new population of desert bighorn in the Upper Dolores Canyon area in San Miguel County with a group of 50 sheep obtained from Nevada. Over time, the herd has grown to number about 150 animals.

In December, sheep captured from this herd were relocated to an area north of the Big Gypsum Valley in Montrose County, about 15 miles away, to augment a small existing herd. If the bighorns do well, biologists may relocate another 15 next year.

"The herd in the upper Dolores River area has been growing, but another herd in some good bighorn habitat just down the canyon isn't doing as well," said Scott Wait, senior terrestrial biologist for the DOW's southwest region in Durango. "Having more animals in more places will improve the long-term outlook for the species. Giving the Middle Dolores herd a boost will help us do that."

Desert bighorns are native to arid regions of the West. These animals -- slightly smaller than the high-country Rocky Mountain bighorns -- are well-adapted to desert canyons.

After capture on Dec. 16, biologists examined each of the transplanted sheep to assess its health and took blood samples. The sheep were then fitted with radio collars to allow biologists to monitor their movements and survival. The sheep were released the next day.

This is the third time the Division has attempted to establish desert bighorn in the Middle Dolores Canyon. Two other attempts, in 1990 and 2001, did not result in the establishment of a new herd. Biologists believe that mountain lion predation played a primary role in the outcome.

Bighorns seek security in steep, perilous terrain. With their specially adapted hooves, they can leap from ledge to ledge and traverse near vertical surfaces at great speed. But it takes time for animals to learn how to find food, water and use steep slopes or cliffs for safety in new terrain. Biologists believe that it may be important to reduce the risk of predation to improve the chances for the new herd to become established.

"We want to keep a close eye on these sheep to see how they're doing," Wait said. "If we start seeing predation, we may need to step in to give these sheep some time to get established."

As a result, the Division asked the Wildlife Commission on Jan. 5 for permission to remove individual mountain lions preying on the Middle Dolores herd for up to 24 months. Commissioners said that if a mountain lion kills more than one sheep, it should be removed. If a lion kills only one sheep, biologists would have the option to remove it.

Prompt initiation of the control effort would help ensure that the individual lion responsible for the sheep predation is removed. If sheep leave the reintroduction area and are killed by a lion, no control action would take place.

There have been no mortalities among the radio-collared sheep since their release on Dec. 17.

"Managing wildlife sometimes means making difficult choices," Wait said. "In this case we know that the mountain lion population is stable in this area and some selective removal won't hurt it. But this will give the bighorns a chance to explore their new territory and get established before they have to worry about getting chased around by lions."

The DOW will monitor the animals closely. Biologists will decide in 2011 if a second transplant will be conducted.

Two other desert sheep herds exist in the state: one in Colorado National Monument west of Grand Junction, and one in the Escalante/Dominguez Canyon area west of Delta.

More information about bighorn sheep may be found at: wildlife.state.co.us/WildlifeSpecies/Profiles/Mammals/BighornSheep.htm

PHOTO AVAILABLE: Go to this link for a photo of the bighorn release.Caption is below. http://dnr.state.co.us/ImageDBImages/26143.jpg

Desert bighorn sheep scamper from trailers after being released just north of the Big Gypsum Valley in Montrose County on Dec. 17, 2010. These sheep were trapped from a herd of about 150 animals in the Slickrock area on Dec. 16. The 15 sheep were released in an area to the north to help augment a small herd in the middle Dolores River Canyon.

Photo: Brad Banulis, Colorado Division of Wildlife