Does the Evolution of Predatory Behavior Alter Stress Response? Insights from a Selection Experiment on Bank Voles

AbstractThe ability to cope with challenging situations, such as the predator-prey interactions, can determine Darwinian fitness. While many studies are concerned with the stress response of prey facing a predator, the stress response of the predator remains unstudied. We hypothesized that evolution of the predatory lifestyle involves adaptive changes in hypothalamic-pituitary-adrenal (HPA) axis regulation and tested this using an experimental evolution model comprising lines of bank voles (Clethrionomys = Myodes glareolus) selected for predatory behavior toward crickets (P lines) and unselected control (C) lines. We measured plasma corticosterone after a cricket-hunting test and a sham test, where the voles experienced identical conditions but without prey. We expected that test conditions would affect corticosterone levels differently depending on the selection line type. However, the effects depended on sex. In males, corticosterone levels were lower than in females and did not differ between selection lines or test types. In females, both factors influenced corticosterone levels: after the sham hunting test, corticosterone levels were higher in P lines than in C lines, suggesting an increased alertness and mobilization. Compared to the sham hunting test, corticosterone levels after the cricket-hunting tests tended to be lower in P lines but higher in C lines. These results suggest that at least in females, the selection for predatory behavior has adaptively altered HPA axis regulation. Given the complexity of the HPA axis, and in particular the role of corticosterone, our study has an exploratory rather than a confirmatory nature, but it opens the prospect for a research direction not yet explored.