Meeting Abstract
The fear of predators can have a wide-range of effects on the behavior, physiology, fitness and demography of animals. One of the primary mechanisms that mediate these effects is considered to be predator-induced changes in glucocorticoid levels. Despite the widespread belief that exposure to predators triggers the physiological stress response, very few studies have measured glucocorticoid responses to predator presence in natural conditions. Among those that have, the results are not consistent, suggesting that the nature of the predator and/or the perception of the predator as a threat could have a significant impact on whether an individual mounts a glucocorticoid response. However, the effects of different predator types or proximities have not been systematically tested in any study. We studied the glucocorticoid response to acute predator exposure in breeding female tree swallows (Tachycineta bicolor). To test the role of predator type in inducing a physiological stress response we compared the glucocorticoid response to raptor mounts (common kestrel: Falco sparverius and sharp-shinned hawk: Accipiter striatus) and mink mounts (Neovison vison) presented outside the nest box, with samples collected from non-predator exposed females. To assess the effect of predator proximity we compared the glucocorticoid response to mink mounts presented outside the nest box with those presented inside the box, along with paired controls. Our results suggest that predator exposure does not universally induce a glucocorticoid stress response, but that the nature of predator exposure matters. These findings have implications for understanding the physiological effect of predator exposure in natural systems, as well as for experimental studies that attempt to manipulate physiological stress through predator exposure.
