Influence of overnight recreation on grizzly bear movement and behavior in Yellowstone National Park

Interactions among recreational users and grizzly bears (Ursus arctos) are a continuous challenge for bear managers. Yellowstone National Park, Wyoming, USA uses a system of designated backcountry campsites to manage overnight use and provides bear-resistant food-storage devices for recreational users. Few studies have evaluated how this type of management and recreation influences grizzly bear behavior. We used global positioning system (GPS) data for humans and bears to determine how overnight use influenced grizzly bear movement behavior. We determined times of day campsites were occupied and contraked grizzly bear locations to random locations near occupied campsites. We conducted a similar analysis ignoring campsite occupancy to assess the utility of including a temporal variable. Grizzly bears were 0.35 times as likely as random locations to be <= 200 m from occupied campsites (95% CI = 0.19-0.62, P <= 0.001). Conversely, when human occupancy was ignored, bears were 2.11 times more likely than random locations to be <= 200 m from campsites (95% CI = 1.85-2.41, P <= 0.001). We conclude that overnight backcountry camping can displace grizzly bears within 200 m of campgrounds. To avoid confounding results, we suggest considering use of a temporal variable in studies of human-bear interactions.