Glucocorticoids are a proxy for internal state, and internal state affects movement and habitat selection. Habitat selection is generally adaptive. However, habitats are often deemed low fitness when selected by animals with atypical or elevated glucocorticoid production. This negative connection stems from the relationship between glucocorticoid production and environmental stressors that reduce fitness. In many cases, however, glucocorticoid production benefits fitness. We argue positive and negative glucocorticoid-fitness relationships can be reconciled through a mechanistic understanding of the adaptive role of glucocorticoids in habitat selection, which we demonstrate by testing the effect of glucocorticoid production on habitat selection by pre-partum and post-partum female elk. If glucocorticoid production is adaptive for elk, their habitat selection should depend on glucocorticoids. Furthermore, the relationship should change between pre- and post-partum when adaptive behaviour shifts from prioritizing their survival of mothers to that of their calves.
Results/Conclusions
We found an adaptive relationship between habitat selection and glucocorticoid production. Pre-partum elk with more glucocorticoids replenished calories after stressful events. They were twice as likely to be found in forage-rich but risky habitat. In contrast, elk with more glucocorticoids avoided risk after parturition. They were two times less likely to be found in the forage-rich habitat and six times more likely to be found in safe habitat for calves. Our results suggest the mechanism by which glucocorticoids influence habitat selection adjusts to life history stage to support fitness. Given this flexible function of glucocorticoids, we recommend changes to how they are used to rate importance of habitats for wildlife. We also present preliminary results showing the habitats individuals select influence their subsequent glucocorticoid production, suggesting glucocorticoids and habitat selection share a feedback relationship. We speculate this feedback relationship is partly responsible for individual differences in stress coping styles and habitat selection.
