Polar Bears International

Cortisol Studies


Sea-ice losses from climate change have dramatically reduced the polar bear’s access to its main prey, ringed seals. Because nutritional stress can influence reproductive success and survival, identifying polar bears undergoing such stress can help scientists and managers monitor the health of individual bears and the effect of sea-ice losses on polar-bear populations.

One way to do this is by studying the levels of cortisol, a blood-borne stress hormone, in samples of polar-bear urine or fur. Our cortisol studies include work with polar bears in zoos and in the wild.

Zoo Bear Cortisol Study

Cortisol monitoring has proven valuable in many species as a measurement of stress, but species-specific baseline patterns must be established before they can be used as a monitoring tool. Polar bears in zoos provide a valuable opportunity to gather such data.

Through non-invasive, opportunistic sampling from zoo bears, scientists have been collecting and analyzing the cortisol concentrations in polar-bear urine throughout the year. The patterns established by this analysis will help scientists and field managers utilize cortisol as an indicator of stress.

This study is being conducted for PBI by Megan Owen, Applied Animal Ecology, Institute for Conservation Research, San Diego Zoo Global, and John Whiteman, Department of Zoology & Physiology, University of Wyoming.

Wild Bear Cortisol Study

During the fasting summer months on land, polar bears grow new fur and incorporate cortisol into their hair. This project is examining the cortisol levels preserved in polar-bear fur as an indicator of their stress levels. Developing less invasive and non-invasive monitoring methods is essential for effective management.

Scientists hypothesize that summer stress will be largely influenced by the a) body condition of the bears at the time of ice breakup, b) the duration of seasonal ice coverage and c) the sex, reproductive status and age of the individual.

Researchers also will link cortisol levels to other indicators such as persistent organic pollutants, heavy metals, and genetic markers to gain new insights into how the population is responding to environmental change. The team will analyze several hundred archived and current samples from polar bears in the Western Hudson Bay population, which live in a seasonal ice area.

Dr. Andrew Derocher of the University of Alberta is leading this study in cooperation with Patrick Mislan, Thea Bechshøft, David Janz, Nick Lunn, and Evan Richardson. Our thanks to Pittsburgh Zoo & PPG Aquarium and Hauser Bears for funding.