Response of American black bears to the non-motorized expansion of a road corridor in Grand Teton National Park

摘要

In 2007, Grand Teton National Park authorized construction of several paved, non-motorized pathways situated within existing road corridors, primarily designed for pedestrian and bicycle use. Construction of the first 13-km section was completed during 2008. The pathway resulted in direct loss of wildlife habitat, new human activities, and a wider zone of human use. We examined how these changes affected American black bear (Ursus americanus) movements, habitat use, activity, corridor crossings, and visibility to human visitors. Thirty (12F, 18M) bears, fitted with global positioning system (GPS) radiocollars, were monitored during 1-3 study periods: pre-pathway (2001-07), construction (2008), and pathway (2009-10). During 2009-10, we deployed 6 trail counters to document human use of the pathway. Counts of humans ranged from 0 to 148 detections/counter/hour. Mean counts peaked during mid-summer (15 Jun-30 Aug) and during midday (1100-1600 hrs). Bears did not shift their home ranges in response to human use of the pathway, nor did they reduce their frequency of corridor crossings. Instead, bears altered the way they used the areas near the corridor. Across the study periods, bears showed greater selection for steep slopes and for areas farther from the corridor, and they were increasingly likely to cross the corridor in areas providing vegetative cover. Near the corridor, bears decreased their activity by approximately 35% during midday and increased their activity by about 10% during morning and evening. Proportion of corridor crossings occurring at night also increased 20-40%. These behavioral changes allowed bears to continue using areas near the corridor while reducing encounter rates with humans on the pathway. However, the observed shift of activity toward morning, evening, and night may increase the likelihood that human-bear encounters would occur during the low light conditions of dawn and dusk and increase the probability of vehicle collisions.