Assessment of cortisol concentrations from wolf hair samples in relation to age, sex, and health status of individuals

Studying cortisol concentrations is important for assessing stress levels in wild animals like wolves. While several studies used scats for hormone assessment, measuring cortisol levels from hair samples may be more suitable for analysing long-term physiological changes of an individual. In this thesis, the hair cortisol concentrations of free-ranging wolves above the age of one year were studied. The hair samples were collected from wolf carcasses recovered in Italy. The main aim was to determine whether sex, age, or health status (determined by body condition and signs of diseases) would have an effect on hair cortisol concentrations. Based on former studies, it was predicted that wolves with poor health status would have higher hair cortisol concentrations than healthy individuals. Concerning sex and age, previous studies did not reveal consistent effects on hair cortisol levels. Additionally, for this thesis, other factors were also considered, such as body mass, season of death, and the province where the individual had been found. Cortisol was extracted and assessed from each hair sample using enzyme immunoassays, and the results were statistically analysed with linear mixed models. Out of all considered factors, only health status was found to affect hair cortisol concentrations significantly - confirming that wolves with poor health status have elevated hair cortisol levels compared to healthier individuals. Neither sex, nor age had a significant effect on hair cortisol concentrations in this study population, and no correlation was discovered with any of the other considered factors.