Roughly 100 bighorn sheep in the Teton Range constitute the most threatened ungulate population in Jackson Hole, according to biologists with the Wyoming Game and Fish Department.

Game and Fish habitat biologist Steve Kilpatrick said Teton bighorn sheep face threats from their small herd size, inbreeding, loss of migration corridors, backcountry recreation and loss of historic winter and summer range.

Kilpatrick gave a presentation on bighorn sheep Wednesday at the Jackson Hole Conservation Alliance office.

Researchers with Game and Fish, Grand Teton National Park, Bridger-Teton National Forest and others are in the early stages of a study on the Teton herd’s food selection, survival to adulthood, seasonal distribution and movement.

From helicopters, researchers will to use nets to capture 20 bighorn sheep, fitting the animals with GPS collars. After two years, the collars will drop off the animals and researchers will retrieve the data.

Kilpatrick said the Teton herd is a remnant of a population that once ranged east to the Gros Ventre Range, west to the Big Holes and Bitch Creek, and south to Palisades Reservoir. Now human development has isolated the population in small, high-elevation habitat in the Tetons.

Thick tree stands, a result of fire suppression efforts, have also ruled out winter migration to less-developed, lower-elevation habitats such as Teton Canyon. To escape predators, bighorns rely on vision that is eight to 10 times as good as humans for an early warning, then they run to nearby cliff bands, Kilpatrick said.

Fire suppression has allowed dense conifer growth, which allows predators to get close to bighorns without being seen.

“When conifers get too dense, [bighorns] leave,” Kilpatrick said.

Just how the animals survive at such a high altitude is a mystery. There’s very little food above 10,000 feet, where the animals live, especially in winter. Kilpatrick said the animals are known to eat lichen off rocks.

“A 4-year-old’s teeth are as worn as a 10- to 12-year-old ram [from another population],” Kilpatrick said.

The animals also have smaller, tightly wound horns.

“They don’t put a lot of energy into making horns,” Kilpatrick said. “They are just trying to survive.”

One advantage to their isolated location is a low incidence of disease. Unlike other herds in Wyoming, Teton bighorns aren’t exposed to a form of bacterial pneumonia that is usually contracted through contact with domestic sheep.

Populations in the Gros Ventre area have also declined, Kilpatrick said. That herd once topped 1,200 animals, according to a survey done in 1935. Now the Gros Ventre herd numbers roughly 300 bighorns.

Part of the study will assess how backcountry skiers, hikers and climbers affect the sheep. The National Park Service has closed some areas such as the Prospectors Mountain and Mount Hunt complex to protect the animals. Rendezvous Peak is another area that is critical for bighorn sheep.

A helicopter contractor hired by researchers tried to capture bighorn sheep for the study in December, but weather conditions made the attempt unsuccessful.
The contractor could try again in mid-February.