Does the evolution of predatory behaviour alter intermale aggression? Insights from a selection experiment on bank voles
Aggression occurs in many forms and can be an important adaptive behaviour. Two distinct forms are predatory and intermale aggression. It remains unclear whether they share genetic and neurobiological regulatory mechanisms and thus whether evolution of one may influence the other. We tested whether selection for increased predatory behaviour leads to increased intermale aggression using an experimental evolution model comprising lines of bank voles (Clethrionomys = Myodes glareolus) selected for high predatory propensity towards crickets (P lines) and unselected control lines (C lines). Adult males were tested in a cricket-hunting test followed by two intermale aggression tests. As expected, P-line males showed higher hunting propensity and performance than C-line males. In the intermale aggression test, a greater proportion of P-line males displayed aggressive behaviours (93% vs. 80%), they did it earlier (mean{+/-}SD: 116 {+/-} 144 s vs. 349 {+/-} 320 s), more frequently (33 {+/-} 38 vs. 12 {+/-} 17), and for longer (92 {+/-} 137 s vs. 31 {+/-} 52 s). P-line males also showed a proactive behavioural profile, whereas C-line males were vigilant, spending more time observing the opponent and staying immobile. These results indicate that predatory and intermale aggression partly share genetic and neural regulatory mechanisms.