The influence of hunting pressure and ecological factors on fecal glucocorticoid metabolites in wild elk

Climate change and human population growth have increased anthropogenic threats to biodiversity and habitat fragmentation. Ecologists and conservationists need tools to assess the effect of these ecological and environmental perturbations on organismal fitness. One possibility is glucocorticoids (e.g., cortisol and corticosterone) which integrate various factors such as anthropogenic disturbances, predation, food, or environmental stressors. Here we tested the hypothesis that fecal glucocorticoid metabolite concentrations (GCMs) in wild female elk (Cervus canadensis) increased as the hunting season progressed. We also examined the influence of year, food availability, and elk group size on fecal GCMs. We found that as the hunting season progressed, fecal GCMs tended to decrease. We also found that as the number of cows in a group increased, GCMs decreased, and found a strong effect of year on fecal GCMs, with samples collected in 2016 having lower fecal GCMs than those collected in 2015, 2017, and 2018. However, yearly variation was not driven by availability of hard mast forage. The lack of positive association between hunting pressure and fecal GCMs and identifying what is driving yearly variation in fecal GCMs warrants further study. We highlight the negative influence of group size, possibly due to vigilance, on fecal GCMs and the importance of examining ecologically relevant covariates to accurately identify main treatment effects.