Quantifying grizzly bear habitat selection in a human disturbed landscape

• Main Author: Stewart, Benjamin Peter
• Other Authors: Nelson, Trisalyn
• Language: English; en
• Published: 2011
• Subjects: Grizzly Bear; GIS; Geography; Conservation; Forest Disturbance; Forest Management
• Online Access: http://hdl.handle.net/1828/3540

Understanding the use of habitat by large carnivores in the presence of ever increasing anthropogenic disturbance is crucial to managing threatened species. In the foothills of the Rocky Mountains in west-central Alberta, Canada the grizzly bear (Ursus arctos) faces such disturbance, and is especially susceptible due to their low fecundity and large home ranges. Grizzly bear mortality increases with proximity to human disturbance, leading to the conclusion that anthropogenic forest disturbance is incompatible with successful grizzly bear habitat The purpose of this research is to evaluate grizzly bear habitat use as it relates to forest disturbance. The general approach was to quantify grizzly bear habitat use and compare to an expectation of use calculated through conditional randomization. The research involved two distinct analyses. First, grizzly bear use of natural edges (transitions between land cover classes) and anthropogenic landscape edges (roads, pipelines, and forest harvests) was quantified and compared between seasons and sex. Females were found to use anthropogenic edges more than natural edges, whereas males used natural edges more. Despite the increased mortality threat arising from increased human access around anthropogenic disturbances, female grizzly bears are using anthropogenic edges more than natural edges, meaning anthropogenic edges may not be incompatible with successful grizzly bear populations. Knowing that female grizzly bears use anthropogenic edges more allows managers to limit access to areas with specific edges desirable to female bears. While creating more disturbances is not the solution to managing for better grizzly bear habitat, limiting human access to areas of beneficial edge could decrease mortality risk. Knowing that grizzly bears use edges, the second analysis quantified use of forest disturbances of varying ages, and determined what disturbance characteristics drive grizzly bear selection of forest disturbances. A 40-year forest disturbance dataset was generated through image differencing of the tasselled cap angle transformation of Landsat imagery (MSS, TM, ETM+). Disturbances were grouped into decades, and compared. Disturbances were labelled as selected or not selected through a randomization process, and selected disturbances were compared to not-selected disturbances using four landscape metrics: disturbance size, disturbance elevation, average tasselled cap transformation greenness, and distance from disturbance to nearest human settlement along a road network. Results indicate that bears select for larger disturbances in all seasons. Females select for disturbances with low remotely-sensed greenness in all seasons, where males select for disturbances with low remotely-sensed greenness in the spring and fall, but high remotely-sensed greenness in the summer. Females select for disturbances at a consistent elevation, whereas males show seasonal variation. Both sexes avoid the most recent disturbances from the 2000s. Females show greater selection of disturbances in the summer and fall, whereas males select disturbances in the fall the least. Knowing that bears select for large disturbances, and females select disturbances at a consistent elevation, forest managers can limit human access to these areas in order to limit human and bear interactions and reduce mortality risk. === Graduate