Grizzly Bear and Human Use at Moth Sites in the Greater Yellowstone Ecosystem

Abstract

In the greater Yellowstone ecosystem (GYE), alpine aggregations of army cutworm moths (Euxoa auxiliaris) are an important food source for grizzly bears (Ursus arctos horribilis). The number of grizzly bears utilizing this food source has increased since initial documentation in 1986 in the Shoshone National Forest, Wyoming. Dozens of bears congregate and feed on moths offering a unique viewing opportunity for bear-enthusiasts, professional media, and hikers. Currently, there is a limited understanding of how bears use these areas and no information on human use. The proximity of grizzly bears and humans poses a management concern for grizzly bears and human safety. Our objectives are to quantify grizzly bear and human use patterns and to identify areas of bear-human interactions. Our methods include occupancy and written surveys, GPS tracking unit deployment, and GIS analysis. Preliminary results from our first year of bear observations (n=220) showed 48% of bears foraging on moths, 20% foraging on vegetation, and 23% travelling. We recorded 5 groups and 26 groups of human use at two locations. We documented 18 bearhuman interactions, all on high-use travel routes common to bears and humans. Despite low human use all interactions between bears and humans resulted in bear avoidance of humans. At present, bear-human interactions appear to be very low but if human use increases, interactions will increase due to lack of alternate travel routes.