Assessment of hair re-growth and the correlation between hair cortisol and faecal glucocorticoid metabolite concentrations in captive wolves

Given the growing interest in wild wolf populations, hormonal profiling is a valuable tool for conservation endocrinology. Hair samples appear as a reliable and practical substrate for hormonal analyses due to their non-invasiveness and storage advantages. As keratinous tissue incorporates hormones over a longer time (weeks to months), it seems suitable for long- term stress evaluation. The hair and faecal samples used for this thesis were collected from seven captive wolves. Their hair was collected using a shave/re-shave study design and additionally brushing. One of the study’s aims was to conduct a comparison of concentrations of glucocorticoids, specifically cortisol, extracted from hair and faecal samples to investigate whether these represent an accurate reflection of systemic levels. In addition, possible confounding factors such as season, body region, or sampling method were analysed. Knowing the approximate time window during which hormonal incorporation into sampled hair occurs also improves their validity as a measure of potential stressors because elevations can be linked to a certain period or even specific stimuli. This requires knowledge of the hair growth pattern in wolves, which has not been investigated before and therefore was another goal of this study. The results demonstrate that hair growth in wolves is seasonally specific with a growth spurt in late summer and autumn. A significant, positive correlation between faecal and hair cortisol concentrations was established, demonstrating that hair cortisol does indeed reflect systemic levels. Body region and season were found to have a significant effect on hair cortisol and should thus be considered when analysing results. These findings add valuable information to the field of non-invasive endocrinology and contribute to future research investigating the systemic levels of cortisol in wild wolves in different contexts.