UBC Theses and Dissertations
Quantifying spatial-temporal change in habitat occupancy patterns of grizzly bears (Ursus arctos) in the context of industrial activities in western Alberta Irwin, Mackenzie Kate
Landscape change is a primary driver of global species decline, requiring effective approaches for monitoring wildlife populations. Occupancy modelling, which estimates the probability of a species being present on a landscape, has become a popular method for monitoring wildlife populations and habitat quality. Among large mammal species in North America, grizzly bears (Ursus arctos) are particularly vulnerable to and threatened by anthropogenic pressures. Using hair-snag data collected in 2004 and 2014 from a threatened grizzly bear population in Alberta, Canada, this research developed single-season occupancy models to understand how anthropogenic disturbance and landscape conditions influence occupancy patterns of male and female grizzly bears over a decade. I then quantified spatial patterns of grizzly bear occupancy and density using measures of spatial autocorrelation to assess relationships between occupancy and density and landscape processes related to anthropogenic disturbance and topography. By examining the spatial relationships between predicted grizzly bear occupancy-abundance estimates over a decade, I was able to provide a better understanding how observed patterns are influenced by disturbance and identify important habitat. Occupancy models showed the average occupancy probability decreased slightly (0.35 to 0.34), despite observed increases in grizzly bear population (36.0 to 71.3 individuals) over a decade. However, spatial patterns of occupancy showed previously unoccupied cells in eastern portions of the study area were colonized from 2004 to 2014. Male occupancy was negatively related to anthropogenic disturbance, including cutblocks and all disturbance, compared to females. Anthropogenic disturbance had an increased influence over time, highlighting the need to consider cumulative effects in occupancy monitoring. Spatial patterns of occupancy and density estimates were similar, with clusters of high occupancy and density occurring where terrain is complex and human access is limited. These areas may act as important source habitat for the population with dispersers occupying potential sink habitats where disturbance and mortality are higher. The occupancy modelling framework and results provide a better understanding of the impacts of anthropogenic disturbance on grizzly bear occupancy and population persistence for regulatory bodies, wildlife managers, and industry, which will contribute to the conservation of grizzly bears and other large carnivores.
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