Black Bear Density and Resource Partitioning with Grizzly Bears

  • Author / Creator
    Loosen, Anne Elizabeth
  • American black bears (Ursus americanus) and grizzly bears (U. arctos) have similar habitat requirements, relying on seasonally available grasses, forbs, fruiting shrubs and trees, and neonate ungulates. To avoid aggressive encounters with grizzly bears, black bears partition habitats spatially and temporally. For example, black bears avoid areas with high-quality resources like spawning salmon (Oncorhynchus spp.) and ungulate carcasses when grizzly bears are present. We used non-invasive genetic sampling to identify unique individuals, sex, and species. We calculated resource-selection functions for each sex and species, contrasting bear ‘use’ locations with ‘available,’ to document seasonal habitat partitioning in southwestern Alberta, Canada. Using covariates from top RSF models, we made all pair-wise combinations of male and female black and grizzly bears (6 total) in a latent selection difference function. We collected bear hair during 7 sample occasions in early summer, late summer, and autumn in 2013 and 2014 in southwestern Alberta. From the top models, black bears avoided recently burned areas (<20 years old) relative to grizzly bears, grizzly bears selected public (Crown) lands, and black bears selected private lands. Western lands in our study area are primarily Crown land and eastern lands are primary private. For all seasons, male and female black bears showed the most overlap in resource selection. In early summer, female grizzly bears and female black bears showed the most overlap. In late summer, male and female black bears showed the most overlap. In autumn, male and female black bears, as well as male grizzly bears and female black bears showed higher overlap relative to other groups. Our results indicate habitat partitioning occurred in southwestern Alberta and clarify how grizzly bears, which are listed as a Threatened species in Alberta, are co-existing with a subordinate, but higher-density species. There has never been an empirical estimate of black bear density and abundance in southwestern Alberta. We used non-invasive genetic sampling and indices of habitat productivity and human disturbance to estimate black bear population density. We used spatially explicit capture-recapture (SECR) and resource-selection functions (RSF) to estimate density and abundance for each year and sex. SECR-derived black bear abundance estimates for males were 149.4 (95% CI: 124.6-179.2) in 2013 and 132.2 (95% CI: = 110.9-157.5) in 2014. SECR-derived abundance estimates for females were 261.4 (95% CI:199.9-341.8) in 2013 and 210.7 (95% CI: 159.3-278.6) in 2014. RSF-derived abundance estimates in the area of inference were 116.1 male black bears (95% CI: 82.3 – 163.9) in 2013 and 134.39 male black bears (95% CI: 98.9 – 182.6) in 2014 (Figure 6). For females in 2013, abundance in the area of inference was 159.5 (95% CI: 120.3 – 211.6) in 2013 and 147.54 (95% CI: 96.0 – 226.8) in 2014. Density estimates were highest on federally and provincially protected lands, followed by private land, and densities were lowest for both sexes on Crown land. With current plans to create two new Provincial Parks on Crown land in our study area, we speculate this could decrease mortality rates, and increase black bear densities on Crown land.

  • Subjects / Keywords
  • Graduation date
    2017-11:Fall 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Biological Sciences
  • Specialization
    • Ecology
  • Supervisor / co-supervisor and their department(s)
    • Boyce, Mark S. (Department of Biological Sciences)
  • Examining committee members and their departments
    • Derocher, Andrew (Department of Biological Sciences)
    • Mathot, Kim (Department of Biological Sciences) *Arms length examiner
    • Nielsen, Scott (Renewable Resources)