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Assessing stress in western Hudson Bay polar bears using hair cortisol concentration as a biomarker Open Access


Other title
body condition
Polar Bear
Ursus maritimus
Hudson Bay
Age effect
climate change
sea ice
Type of item
Degree grantor
University of Alberta
Author or creator
Mislan, Patrick
Supervisor and department
St. Louis, Vincent (Biological Sciences)
Derocher, Andrew (Biological Sciences)
Examining committee member and department
Hik, David (Biological Sciences)
Department of Biological Sciences
Date accepted
Graduation date
Master of Science
Degree level
The development of novel biomarkers to help assess whether polar bear (Ursus maritimus) health is impacted by long-term physiological stress associated with climate change represents an emerging area of research. With progressively greater reductions in sea ice cover and a corresponding decrease in food availability, polar bears are likely to experience high levels of stress. While stress is adaptive in the short term, chronic stress can have deleterious effects, which may impair individual and population level health. Cortisol is the principal effector hormone of the stress response and has previously been linked to aspects of polar bear biology (e.g. reproduction, growth) that have been shown to be negatively influenced by environmental change. Understanding stress is important for polar bears at the southern limit of their range, such as those in western Hudson Bay (WH), where changing sea ice phenology threatens population viability. We examined the relationship between the biological and demographic variables of age, reproductive status, and body condition (fatness) and hair cortisol concentration (HCC) in 729 polar bears in WH sampled from 2004 - 2013. Overall, there was a negative relationship between fatness and HCC, suggesting that bears in poorer body condition experienced higher levels of stress. However, when reproductive status was included in our analysis, this relationship only held for male and lone female bears. Females with dependent offspring had consistently low fatness and elevated HCC, likely because of the high cost of maternal care. We also found a positive correlation between HCC and age for bears in: 1) poorer body condition, possibly due to nutritional stress compounding effects of aging; and 2) male bears, potentially due to stress and injury associated with intrasexual mate competition. These findings support the use of HCC as a biomarker for polar bear health. Furthermore, we have established a HCC benchmark against which future effects of continued climate change on polar bear health can be measured.
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. 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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