Michael Proctor, Birchdale Ecological

The influence of bottom-up resources and top-down mortality risk underlies the demographic trajectory of wildlife populations. For species at risk, understanding factors driving population dynamics is crucial to effective management and, ultimately, conservation. We explored the relationship between availability of the dominant food resource and mortality risk across 3 grizzly bear (Ursus arctos) populations in British Columbia, Canada. We integrated analyses of bottom-up and top-down demographic parameters from DNA and GPS telemetry data to understand and inform a comprehensive efficient management paradigm across the region. We modeled important huckleberry (Vaccinium membranaceum) patches and looked at their influence on habitat selection, bear density and female fitness in relation to mortality risk in each of those realms. Huckleberry patches were identified by following 43 GPS collared bears over 10 years. Habitat selection was explored through ecological modeling and density through Spatial Capture Recapture modeling. Female fitness was linked to huckleberries, habitat and mortality risk through extensive family pedigrees across 20 years that revealed reproductive success. In all 3 analyses huckleberry patches were the most influential bottom-up factor and secure habitat was the most consistent top-down variable. These results suggest that both bottom-up and top-down forces drive several population processes of grizzly bears in the region, especially for females. We found that 38% of huckleberry patches were in non-secure habitat and that these patches were associated with lower fitness and density relative to those in secure habitat. Bears were effectively not utilizing their most important food source when they were within 500m of an open road, revealing bottom-up resources being impacted by top-down mortality risk. An examination with population-level metrics such as density, vital rates, and fitness may be needed for effective conservation management.