Scientists: Teton Range bighorn herd at risk

JACKSON, Wyo. (AP) - The roughly 100 animals that make up the isolated Teton Range bighorn sheep herd are at risk of extinction because they no longer migrate from their tough high-mountain habitat during the winter and are genetically isolated, scientists said.

The herd used to migrate every winter from the high peaks of the Tetons to lower, warmer climes.

The herd stopped migrating after about 1950 as development and domestic sheep grazing increased at lower elevations, said biologist Aly Courtemanch, a University of Wyoming master's degree candidate working for the Wyoming Cooperative Fish and Wildlife Research Unit.

"Their winter range was taken over by houses and roads," she said.

Courtemanch and other researchers are using tracking devices and help from backcountry skiers to learn how the herd survives harsh temperatures and sparse winter habitat. It's the most recent effort of the Teton Bighorn Sheep Working Group, which formed in the early 1990s.

Public lands managers have closed some backcountry terrain to skiers, including Static Peak and Prospectors Mountain, to reduce the animals' exposure to humans.

Researchers say the sheep react badly to people. Given the lack of food during winter in the Tetons, a disturbance by a backcountry skier could cause sheep to burn enough calories to die.

Researchers collared 28 adult female sheep in February 2008 and March 2009. The collars contain tracking devices and radio transmitters to give researchers insight into the herd's movements.

The researchers also took hair, blood and fecal samples to find information about what the animals eat and the level of inbreeding.

The researchers have also handed out tracking devices to backcountry skiers at Jackson Hole Mountain Resort gates and trailheads in Grand Teton National Park and on the Bridger-Teton and Caribou-Targhee national forests.

The researchers plan to compare the tracking data on the sheep and skiers to see if overlap occurs.

Genetic isolation poses a significant threat to the sheep.

Steve Cain, senior wildlife biologist for Grand Teton National Park, said preliminary genetic data shows the herd is actually two distinct breeding populations that are not interbreeding. Inbreeding usually reduces fitness, Cain said.

"It's a very sensitive resource that has a reasonably high probability, statistically speaking, of going extinct," he said.

Some backcountry skiers have been reluctant to participate in the researchers' effort to monitor their skiing paths, because they don't want the information to contribute to closing access in the area. But researchers say the herd is too fragile to ignore.

"We could lose this sheep population for sure," Courtemanch says. "People who live here should be able to balance their skiing with having an intact ecosystem."