Researcher Aly Courtemanch starts her work day on skis. That’s how she gets around on the alpine terrain where she studies the Teton Range bighorn sheep herd. Using GPS devices and trail counters, Courtemanch a scientist at the Cooperative Fish & Wildlife Research Unit at the University of Wyoming, tracks the movemnts of both sheep and skiers. "We really want to get a better sense of how bighorn sheep survive in the Tetons, both summer and winter,” she said. “We don't know very much about this bighorn sheep herd, it's really small and really hard to study because they're so remote and hard to observe." While other wild sheep move down to more moderate terrain, this herd winteres at some of the highest elevations in Wyoming. But they’ve stopped migrating about 60 years ago due to human development, firs suppression and other factors. In this edition of This American Land researchers take a look at this species on the brink of extinction.