Brown bear (Ursus arctos) activity along salmon (Oncorhynchus spp.) streams has frequently been characterized as crepuscular. Suggested explanations include: responses to daily changes in salmon abundance, responses to daily cycles of light and temperature, natural feeding schedules, and avoidance of people. We investigated the last hypothesis by comparing bear activity at 2 adjacent streams in Katmai National Park, both spawning habitat for the same run of sockeye salmon (Oncorhynchus nerka) but differing in their levels of human use. During 1989 and 1991, bear activity at Margot Creek, where no human activity was observed, was distributed uniformly throughout the day (based on 240 observation hours; P > 0.90 both years). This uniform distribution contrasted with the crepuscular pattern of bear activity observed at Brooks River, where human use came from a 60-person lodge, a 60-person campground (20 sites), and substantial day-use. Significant differences (P < 0.001) in activity by time of day were found at Brooks River during the autumn salmon spawning period (sampled 1988-92, 905 observation hr). The midday depression in activity was greatest for bears less tolerant of people (>68% of the adult bears seen). As human activity increased over the years of the study, these shier bears shifted their stream use among time periods: midday activity decreased while activity during the 2000-2200 hour time block increased significantly (P < 0.050). Our results indicated that avoidance of people cannot be discounted as a factor contributing to observed crepuscular patterns of use in brown bears.
- Volume 10
- Issue
- Pages 547-555
- Publication Date 1 January 1998
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- File Size 852.21 KB
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