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

• Author / Creator

  Mislan, Patrick

• 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.

• Subjects / Keywords

  • Hudson Bay
  • Climate change
  • Sea ice
  • Glucocorticoid
  • Body condition
  • Stress
  • Cortisol
  • Ursus maritimus
  • Polar bears
  • Age effect
  • Hormone

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3WS8HV09

• 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.