Abstract
Fecal glucocorticoid assays provide a potentially useful, noninvasive means to study physiological responses of wildlife to various stressors. Consequently we quantified fecal glucocorticoid concentrations among free-ranging elk (Cervus elaphus) by subherd, sex, and season and determined their relationship to various human activities and environmental conditions. Using a validated technique, we assayed 558 fecal samples collected from 30 radiocollared elk in the Black Hills, South Dakota, from June 1995 to September 1997. Fecal glucocorticoid measures were least in winter (x̄=17.41 ng/g, SE=2.97 for bull subherds and 18.9 ng/g, SE=2.85 for cow subherds) and increased to peak concentrations in summer (x̄=33.6 ng/g, SE=3.42 for bull subherds and 34.21 ng/g, SE=3.71 for cow subherds). Vehicle use along primary roads, primary road density, and mean temperature each independently explained a significant portion of the variation in fecal glucocorticoid concentrations ($r^{2}=0.61,\ F_{2,\ 557}=286.13$, P<0.001). Annual glucocorticoid secretion also may be related to normal seasonal metabolic rhythms. Though more research is needed on fecal glucocorticoid concentrations of undisturbed elk, we hypothesize that human activities, high temperatures, or normal seasonal metabolic rhythms may have elevated summer glucocorticoid concentrations. Our findings suggested that fecal glucocorticoid assays, if coupled with population performance measures, could assess physiological effects of natural and human-induced disturbances on free-ranging elk. Also, our study illustrated the need for caution when interpreting fecal glucocorticoid measurements, because several confounding factors may influence interpretation.