Meeting Abstract
Individuals often vary markedly in their stress resilience, but the drivers of this variation remain poorly understood. The glucocorticoid stress response is one of the primary mediators of the phenotypic stress response. Increases in glucocorticoids can help organisms respond effectively to immediate stressors, but can also impair reproduction. While a number of previous studies have tested whether the magnitude of the stress response predicts its performance effects – with mixed results – much less is known about variation in negative feedback efficacy. Here we tested whether stress resilience is predicted by individual variation in the magnitude of the acute stress response, or by the ability to rapidly and effectively terminate that response through negative feedback. Prior to the start of the experiment, incubating female tree swallows (Tachycineta bicolor) were subjected to a capture-handling-restraint protocol to measure baseline corticosterone, the stress response, and the efficacy of negative feedback (via a dexamethasone suppression test). We then exposed birds to one of two experimental stressors: a reduction in flight efficiency, or a simulated increase in predation risk. Negative feedback efficacy before treatment exposure – but not stress-induced corticosterone levels – predicted stress resilience for females in both stressor treatments. Stress-exposed females with stronger negative feedback were less likely to abandon their nests during incubation. In control females, abandonment was unrelated to glucocorticoid levels. These results indicate that variation in the ability to rapidly and effectively terminate the stress response may be an under-appreciated mediator of stress susceptibility in vertebrates.
