The Adrenal Cortisol Response to Increasing Ambient Temperature in Polar Bears ( Ursus maritimus )

• Published in: Animals
• Main Authors: Emily M. Leishman, Maria Franke, Jill Marvin, Dylan McCart, Carol Bradford, Zoltan S. Gyimesi, Anne Nichols, Marie-Pierre Lessard, David Page, C-Jae Breiter, Laura H. Graham
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: thermoregulation; climate change; glucocorticoid; HPA axis; conservation; Veterinary medicine; SF600-1100; Zoology; QL1-991; Ursus maritimus
• Online Access: https://doi.org/10.3390/ani12060672; https://doaj.org/article/f22fa5d891284a06841e7b19aa12a4c9

Our objective was to identify the upper ambient temperature threshold that triggers an increase in cortisol in response to increased thermoregulatory demands in polar bears. The results reported here include endocrine data collected over two years from 25 polar bears housed in 11 accredited zoological institutions across North America. The effects of ambient temperature, sex, age group (juvenile, adult, elderly), breeding season and humidity on fecal cortisol metabolite (FCM) concentrations (N = 8439 samples) were evaluated using linear mixed models. Ambient temperatures were placed into five different categories: <5 °C, 6–10 °C, 11–15 °C, 16–20 °C, and >20 °C. Ambient temperature and humidity had a significant ( p < 0.05) effect on FCM concentrations with significant ( p < 0.05) interactions of sex, age and breeding season. Once biotic factors were accounted for, there was a significant ( p < 0.05) increase in FCM concentrations associated with ambient temperatures above 20 °C in adult polar bears. The implications of these findings for the management of both zoo and wild polar bears are discussed.