Dall sheep (Ovis dalli dalli), grizzly bear (Ursus arctos) and wolf (Canis lupus) interactions in the Northern Richardson Mountains, Canada

  • Author / Creator
    Lambert Koizumi, Catherine M S
  • Assessing the impact of predators on a prey population is inherently challenging, a fortiori in remote ecosystems. With this thesis, I studied the interactions between a recently declining Dall sheep (Ovis dalli dalli) population and two predators: grizzly bears (Ursus arctos) and wolves (Canis lupus), in the secluded Northern Richardson Mountains, Canada. After reviewing the status of this Dall sheep population, I investigated its interactions with grizzly bears and wolves –mostly the indirect effects of predation; using satellite telemetry, habitat utilization analyses, δ13C and δ15N stable isotopes, behavioural observations, and the documentation of Gwich’in and Inuvialuit Traditional Ecological Knowledge (TEK).
    At the spatial level, Dall sheep were in close association with grizzly bears in intensively used areas, although wolves were more likely to be encountered elsewhere. Individual predators also showed various levels of spatial associations with Dall sheep. Based on stable isotope analyses, both predators have a remarkably diverse diet and consume Dall sheep, albeit not predominantly. Animal sources composed most of the grizzly bear diet, with vegetation and aquatic browsers (beavers and moose) constituting the two most important consumed groups. Aquatic browsers constituted the wolves’ principal food, followed closely by mountain mammals (arctic ground squirrels, caribou and Dall sheep). At the behavioural level, the habitat utilization patterns of rams appeared to be guided by foraging needs, whereas ewes were predominantly influenced by predator avoidance. In early summer, ewes foraged longer, were more vigilant, rested less, and exhibited less dominance behaviour than rams, which were exposed to higher predation risk and stayed in smaller groups. TEK complemented and enriched this research, notably regarding historical population trends, habitat utilization, and predator-prey relationships.
    Ultimately, this thesis highlights the complexity and plurality of factors affecting Dall sheep behaviour and their interactions with grizzly bears and wolves. It also emphasizes the individual variability within each species and the several predator avoidance strategies used by Dall sheep to reduce their vulnerability. Although my research was not designed to assess the role of predation in driving this population, historical data stress the imminent contribution of harvest to past abundance fluctuations. More frequent monitoring would help disentangling the effects of various factors on this population.

  • Subjects / Keywords
  • Graduation date
    Fall 2012
  • Type of Item
  • Degree
    Doctor of Philosophy
  • 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
  • Specialization
    • Ecology
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Cassady St.Clair, Colleen (Biological Sciences)
    • Hik, David (Biological Sciences
    • Musiani, Marco (Environmental Design and Veterinary Medicine, University of Calgary)
    • Derocher, Andrew E (Biological Sciences)
    • Parlee, Brenda (Resource Economics and Environmental Sociology)
    • Merrill, Evelyn (Biological Sciences)