Predator-Induced Edge-Drilling Behaviour of emChicoreus dilectus/em (Gastropoda: Muricidae)

The duration of drilling attacks on bivalve prey by muricid gastropods is largely a function of shell thickness at the drilling site selected by the predator. Attacks initiated at the thin valve edges (edge drilling) take significantly less time than drilling through the thicker shell wall (wall drilling). Here, we demonstrate experimentally that the muricid Chicoreus dilectus (Adams, 1885) employs the edge-drilling mode of attack nearly three times more often than wall drilling when exposed to chemical cues from the shell-crushing stone crab Menippe mercenaria , one of its natural enemies, than when foraging in isolation. Chicoreus dilectus is also known to edge drill more frequently in the presence of conspecific snails, which represent competitors for food as well as potential cannibals. Together, these findings suggest that edge drilling by C. dilectus should be considered as a general behavioural response to enemies instead of a specialized response to conspecific enemies. Although all snails exposed to stone crabs expressed the edge-drilling behaviour at least once, wall drilling was still more commonly used by each of these snails, suggesting that there are constraints on behavioural plasticity in the expression of edge drilling.