Stress in Polar Bears?

An important aspect of animal husbandry is investigating how animals react to changes, routines and environments. In most cases, animals adapt well to changing situations. However, in order to scientifically evaluate wellbeing or if an animal is chronically "stressed", zoo biologists have various "tools" available. The first and certainly the most meaningful is "observed behaviour". Variable behaviour and social skills are a good sign of adaptation. But hormones, especially the stress hormone cortisol, also help us to assess situations. While high cortisol levels are normal in acutely stressful situations, high levels over long periods are a sign of chronic stress. This, in turn, is hazardous to health. Cortisol can be measured in the animals’ blood, faeces, saliva and hair. However, in order to interpret the values accurately, in relation to potential stress levels, validation is required, which can only be acquired by means of research.

Our Contribution

... how can stress be measured objectively in polar bears?

This question is the subject of a research project supervised by the Nuremberg Zoo and supported by the Assoc. Friend of the Nuremberg Zoo. Throughout the project, hair and faecal samples from polar bears (Ursus maritimus) were collected in 18 European zoos, in order to measure the "stress hormone" cortisol. While faeces are easy to collect, hair samples could only be obtained via extensive training. The polar bears were trained to present their neck so a small amount of hair could be shaved (see picture). Different methods of cortisol analysis were compared in order to establish a test procedure with which cortisol could be reliably calculated. The long-term cortisol profiles that were created for various zoo polar bears during the study provided basic information on the hormonal balance of polar bears and thus provided also important information for interpreting data from wild polar bears.