Meeting Abstract
It is widely appreciated that glucocorticoid levels are impacted by environmental factors such as weather conditions, food availability, the degree of competition over some limited resource, and predation risk. These changes in glucocorticoids can in turn mediate plasticity in behavioral or life history traits that increase the ability of an organism to persist through environmental fluctuations. Although numerous studies have documented the impacts of specific environmental factors on glucocorticoid levels in a wide-variety of organisms, few studies have simultaneously investigated the relative impacts of multiple ecological factors on glucocorticoid levels. Given that free-living animals likely experience environments in which multiple ecological factors are changing in unison, it is important to assess whether their effects are additive, interactive, or mitigating. For example, an increased predation risk may typically be associated with increased glucocorticoid levels in prey but those effects may be mitigated or eliminated by a simultaneous increase in per capita food availability. We assessed the relative effects of weather conditions, food availability, competition, and predation risk on fecal glucocorticoid metabolite levels of North American red squirrels in the Yukon, Canada. We will describe the results from these analyses that use >10 years of fecal glucocorticoid metabolite data collected from free-living red squirrels that experienced natural and experimental variation in weather, food, competition, and predation risk. By doing so, we illustrate the importance of testing multiple hypotheses regarding the ecological causes of variation in glucocorticoid levels of wild animals.
