Impacts of Human Activity on Bighorn Sheep

During 1996–1998, a study conducted by Montana State University evaluated the potential impacts of road realignment and human recreation on the Mount Everts winter range bighorn sheep. Radio-collars on 18 sheep were used to determine migration routes, lambing sites, high use areas, and watering sites. This was the first study to use radio-collars on sheep in Yellowstone, and it established a baseline of information on the timing of sheep movements, specific migration corridors, and behavior. Samples were taken for future genetic work. Noninvasive techniques (e.g., behavioral observations, fecal lungworm counts, and fecal corticosterone levels) were used to assess the effects of human disturbance on sheep. The most obvious disturbances to sheep observed were aircraft flights, motorized vehicles, humans on foot, and predators. Road corridors with traffic disturbed ewes with lambs attempting to return to the McMinn Bench area in the summer. Recommendations included installing natural guardrails to allow easier movements and implementing aircraft flight regulations to decrease disturbances. The study concluded that the realignment of the current Gardiner–Mammoth road west of the Gardner River could increase available watering areas and winter habitat in places where it may currently act as a barrier, but could interfere with range use or increase disturbances of ewe groups on McMinn Bench.