The influence of prey abundance and risk-sensitive behavioral change on individual access to high-energy food (salmon): Impacts on the density and viability of bear populations

Brown bears are often considered solitary; however, high-density aggregations on coastal salmon runs provide an opportunity to study their behavioral responses in close proximity to other adult bears. Domination of the best feeding sites, and human avoidance, by large males has consistently been reported. In this study I observed displacement of subordinate age/sex classes in time rather than space: large males were less active during the viewing day while females with cubs tended to be more at this time. Females with cubs showed a peak in activity during the earliest viewing period. However, when this period had no viewing activity, this vulnerable age/sex class did not approach and fish, even though large males had left the area. Contrary to my expectation, when freed from the potential threat of large male bears, females with cubs showed no measurable impact of human activity on feeding behavior.; I measured declines in salmon consumption under different risk scenarios; these declines occurred despite superabundant food. Risk avoidance reduced daily salmon consumption by females with cubs by more than one third. By associating with people, females with cubs were able to avoid encounters with large, potentially aggressive males, which dramatically avoided people in both time and space. This is the first study to quantify the energetic cost of intea-specific risk-avoidance for a large carnivore.; Stable isotope ratio mass spectrometry of hair samples collected in the Glendale/Tom Browne drainage indicated that these bears were more salmon dependent than any other population yet studied. Results from this analysis, however, failed to correlate with observed foraging behavior, salmon consumption or salmon availability. For this technique to be effective in the investigation of inter-annual and between individual differences in feeding behavior, we require a better understanding of how brown bear physiology, especially hibernation physiology, and body condition affect stable isotope enrichment and depletion.; Finally, for bears, there is a strong negative relationship between minimum viable population and food availability/habitat quality. My empirical analysis provides supports for a conceptual relationship that has been proposed across species.