Does the evolution of predatory behaviour alter stress response? Insights from a selection experiment on bank voles

The ability to cope with challenging situations, such as the predator-prey interactions, can determine Darwinian fitness. While many studies concerned the stress response of prey facing a predator, the stress response of the predator remains understudied. We hypothesised that evolution of predatory lifestyle involves adaptive changes in the HPA axis regulation and tested this using an experimental evolution model comprising lines of bank voles ( Clethrionomys = Myodes glareolus ) selected for predatory behaviour towards crickets (P-lines) and unselected control lines (C-lines). We measured plasma corticosterone after a cricket hunting test and a sham test, where the voles experienced identical conditions but without prey. The test conditions affected corticosterone levels differently depending on the selection linetype and sex (significant interactions). After the sham hunting test, corticosterone level was significantly higher in P-lines than in C-lines, suggesting an increased alertness and mobilisation. Following the cricket hunting test, corticosterone levels tended to decrease in P-lines, but to increase in C-lines, although not significantly. These results support the hypothesis that selection for predatory behaviour has adaptively altered the HPA axis regulation. However, these effects were primarily driven by differences in females, highlighting the need to consider sex differences in studies of stress physiology.