The quantification of glucocorticoid metabolites in hair is a non-invasive tool that provides important information regarding the endocrine status and represents a valuable method for studying potential stressors that may affect carnivores under both natural and non-natural conditions. Cortisol is the main glucocorticoid hormone of the hypothalamic-pituitary-adrenal gland axis and is considered a standard stress indicator for animal welfare. The current study aimed to compare cortisol levels extracted from hair of both dead, frozen European wildcats (Felis silvestris silvestris) and living feral individuals (Felis silvestris catus) living in different environmental conditions. The results obtained revealed that wild individuals exhibited a significantly (p < 0.001) higher cortisol concentration (n = 15, mean ± SD = 8.91 ± 4.48 pg/mg) than feral ones (n = 10, mean ± SD = 3.57 ± 1.25 pg/mg), probably as a result of both the physiological and/or environmental factors to which each subspecies was subject. This is the first study in which cortisol concentrations have been compared within the Felis silvestris subspecies, thus enriching the scarce information available for the Felidae. Nevertheless, further research is needed to better understand the various physiological and ecological factors affecting the adrenocortical activity of species or populations living in different environmental contexts.
