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


Other title
Canis lupus
Ursus arctos
Sexual segregation
Traditional ecological knowledge
Ovis dalli dalli
Northwest Territories
Carbon and nitrogen stable isotopes analysis
Vigilance behaviour
Nutritional ecology
Home range overlap
Predator-prey interactions
Yukon Territory
Dall sheep
Habitat utilization analysis
Indirect effects of predation
Grizzly bear
Type of item
Degree grantor
University of Alberta
Author or creator
Lambert Koizumi, Catherine M S
Supervisor and department
Derocher, Andrew E (Biological Sciences)
Examining committee member and department
Cassady St.Clair, Colleen (Biological Sciences)
Musiani, Marco (Environmental Design and Veterinary Medicine, University of Calgary)
Parlee, Brenda (Resource Economics and Environmental Sociology)
Merrill, Evelyn (Biological Sciences)
Hik, David (Biological Sciences
Derocher, Andrew E (Biological Sciences)
Department of Biological Sciences
Date accepted
Graduation date
Doctor of Philosophy
Degree level
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.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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