Abstract 249 – Forestry practices influence black bear and grizzly bear occurrence and co-occurrence with prey species in harvest blocks

Tracy McKay and Laura Finnegan

Forest harvesting is a primary agent of change across the boreal forest of Canada, altering black
bear and grizzly bear habitat. Silviculture practices applied after forest harvesting directly
impact forage availability for bears, but there is limited research on how specific silviculture
treatments (preparation, planting, tending) influence bear use of harvest blocks and co-
occurrence with other species. We used camera detections, silviculture data, landscape
characteristics, and vegetation data from 117 harvest blocks sampled in Alberta, Canada during
2018-2020 to assess the influence of silviculture practices, block characteristics, surrounding
habitat, and forage abundance on black bear and grizzly bear occurrence and co-occurrence
with prey species. We found black bear occurrence was higher in blocks that had been planted,
and grizzly bear occurrence was higher in blocks that had been stand tended and with higher
tree-planting densities. Black bear occurrence was higher in smaller blocks, and grizzly bear
occurrence was higher in blocks where the surrounding area had lower densities of linear
disturbances and harvest blocks. Black bear occurrence was higher in blocks with greater
availability of fireweed, and both black and grizzly bear occurrence was higher in blocks with
greater availability of rose. Co-occurrence analysis indicated that black bear occurrence was
higher in blocks where white-tailed deer were detected, and grizzly bear occurrence was higher
where mule deer were detected. Our study indicates that bear use of harvest blocks is driven by
fine-scale block characteristics and silviculture practices as well as the habitat surrounding the
block, and harvest blocks may directly influence predator-prey dynamics. The results of our
study may be used to inform sustainable forest management that considers the impacts of
forest harvesting practices on black bears, grizzly bears, and their prey species.