Measuring the weight of a brown bear hair sample (fot. Agnieszka Sergiel)

Further hormone analysis in the AnthroBear project

Collecting, storing, and processing brown bear hair samples for hormone analysis

Investigating physiological stress is one of the key links between anthropogenic perturbations and population dynamics in wildlife ecology and management. In blood, saliva, and faeces, stress can be measured using glucocorticoids (stress hormones) concentrations, especially cortisol. Using these matrices one can investigate acute stress, while chronic stress requires repeated sampling, which may have field, ethical, and time constrains, especially when studying free-ranging large carnivores.

Hair cortisol concentration is considered a retrospective biomarker of stress covering a period up to few months, depending on the hair growth rate and molting. Circulating short-term cortisol peaks and baseline levels are incorporated into the shaft primarily during anagen (e.g., the active growth phase). The duration of anagen lasts weeks to months depending on the species. Collecting hair samples can be accomplished using minimally invasive sampling techniques, and samples are also easy to store, making research using this matrix easier and more effective. Higher cortisol levels during acute stress shift energy towards the functions needed to cope with the stressor quickly. These changes are usually temporary, and cortisol levels then return to baseline. If the stress persists (becomes chronic), elevated cortisol levels may have deleterious consequences, altering immune function, individual fitness, reproductive success, and ultimately population dynamics.

As a part of the study examining the impact of human settlement and anthropogenic activities on the adrenal gland and gonadal activity, within the frames of AnthroBear Project, we are measuring hair cortisol, testosterone, and progesterone levels in brown bears. Dr. Ghulam Nabi attended the sampling season in Croatia and took part in collecting and storing hair samples, learning about principles of preserving keratinous tissues. Furthermore, he was also trained in processing hair samples starting from its cleaning through weighing and washing to grinding. The hair samples collected for the purposes of the project are now under analysis in collaborating laboratory at the University of Saskatchewan in Canada.