Evaluating the ecological consequences of human land-use on grizzly bears in southwest Yukon, Canada

Abstract

This study investigated the effects of human land-use on grizzly bear (Ursus arctos L.) habitat and populations in the Kluane region of southwest Yukon, Canada. Previous studies in the region identify grizzlies as the species most at risk from cumulative impacts of human activity . The goals of this project were to: 1) identify the effects of cumulative human activities on grizzly habitat and populations; and 2) provide recommendations on human-use management with respect to the conservation of grizzlies and their habitat. Thus , I investigated three aspects of bear ecology and synthesized them to examine the influence of human-activities on bears. First, I examined the appropriateness of using Tasselled Cap Transformation variables for representing the distribution of bear forage. Tasselled Cap layers correlated with aggregate measures of forage abundance, provided continuous variables for linear occupancy estimation models, and were more cost-effective to produce than land cover classifications . I then tested the influence of conspecific distribution on habitat selection by grizzly bear sex/age cohorts . Family groups segregated from other cohorts, in part, to avoid intra-specific aggression and to protect cubs. Segregation also occurred because of differential response by each cohort to the distribution of human activity, and the distribution of forage. I next examined the temporal trends and spatial characteristics of grizzly bear mortality in Kluane. While efforts reduced the frequency of occurrences and management-related mortalities, there was a substantial lag between the management efforts and the decline of human bear interactions and human-caused bear mortalities. Increased human activity in the region may have negated the positive effects of landfill closures. Finally , to examine the influence habitat and mortality models had on grizzly bear productivity and survival, I compared the explanatory power of empirical habitat models based on grizzly bear telemetry relocations or forage availability against expert-opinion models. I used the best model, established by model selection criteria, for explaining reproductive and survival rates to predict population status for grizzly bears in Kluane . Survival and productivity of grizzly bears decreased on the periphery of the protected area adjacent to the highways. While productivity in the areas adjacent to the highways was relatively high, mortality was also high . These areas, therefore, were acting like attractive sinks. Reducing human-caused mortality on the Park periphery and developing a transboundary management strategy will be necessary to conserve grizzly bears in Kluane.