Hair cortisol concentration reflects the life cycle and management of grey wolves across four European populations (original) (raw)

The grey wolf (Canis lupus) persists in a variety of human-dominated landscapes and is subjected to various legal management regimes throughout Europe. Our aim was to assess the effects of intrinsic and methodological determinants on the hair cortisol concentration (HCC) of wolves from four European populations under different legal management. We determined HCC by an enzymelinked immune assay in 259 hair samples of 133 wolves from the Iberian, Alpine, Dinaric-Balkan, and Scandinavian populations. The HCC showed significant differences between body regions. Mean HCC in lumbar guard hair was 11.6 ± 9.7 pg/mg (range 1.6-108.8 pg/mg). Wolves from the Dinaric-Balkan and Scandinavian populations showed significantly higher HCC than Iberian wolves, suggesting that harvest policies could reflected in the level of chronic stress. A significant negative relationship with body size was found. The seasonal, sex and age patterns are consistent with other studies, supporting HCC as a biomarker of chronic stress in wolves for a retrospective time frame of several weeks. Our results highlight the need for standardization of sampling and analytical techniques to ensure the value of HCC in informing management at a continental scale. The mechanisms by which the degradation of natural habitats influences wild animals can require an understanding of their physiological responses to stressors 1. Stressors can be defined as somatic or psychological challenges to homeostasis that first activate the sympathetic nervous system and then the hypothalamus-pituitary-adrenal (HPA) axis 2. As a result, stressors increase the levels of glucocorticoids in the organism 3. While glucocorticoids are commonly used as biomarkers of chronic stress, their usefulness in wildlife is limited due to the influence of short-term stressors, such as capture, on their concentrations in the most commonly used biological matrixes, namely serum, feces, saliva, and urine 4-6. In this regard, the quantification of cortisol, the major glucocorticoid in many mammal species, in hair is emerging as a useful biomarker of chronic stress in wildlife 4,6. While the mechanisms by which cortisol is incorporated in hair remain to be demonstrated, hair cortisol concentration (HCC) is hypothesized to reflect the integrated biologically active free cortisol fraction (not bound to glucocorticoid-binding globulin) rather than the total cortisol concentration in serum 4,7,8. Indeed, several studies have found good correlations between cortisol concentration in hair and simultaneous serial samples of conventional biological matrices such as blood, saliva, or feces 8-10 .