A late September view of the Tetons looking south towards the Grand. Photo: Aidan Whitelaw

Something must give in Wyoming’s Tetons. An interagency working group has proposed that some prime backcountry ski terrain in Grand Teton National Park (GTNP) and surrounding National Forests be off-limits to seasonal winter use to protect high-value bighorn sheep habitat.

At issue are an endemic herd of Teton sheep and their disturbed winter range. The herds, split between north and south sub-groups, number approximately 100-125 individuals in total and are at risk of local extinction. The Teton sheep were once migratory, but as those traditional migratory routes were disturbed, they became year-round Teton residents.

A 2014 masters’ thesis (Courtemanch 2014) showed backcountry skiers stress sheep causing them to move off their preferred habitat. The disturbance isn’t willy-nilly habitat destruction but subtle sheep-human interactions. We may think of ourselves as silent sport participants, which in most instances we are, but silent sport, in this context, may be too loud and intrusive for Teton sheep.

“Individual bighorn sheep exposed to high levels of recreation exhibited increased daily movement rates and home range sizes compared to sheep exposed to low or no recreation. These results reveal that bighorn sheep appear to be sensitive to forms of recreation which people largely perceive as having minimal impact to wildlife, such as backcountry skiing,” reads Courtemanch’s thesis on pages 1-2.

The sheep’s “avoidance behavior” adds stress, which in winter can unduly compromise an animal’s health. The working group has also cited other factors adversely impacting the sheep like climate change, and disease transmission from mountain goats.

An broad overview of the proposed impacted areas in the Tetons. Screen capture image from Teton Working Group presentation.