Oyster drills Stramonita haemastoma use mechanical cues to make foraging decisions

Abstract

To forage effectively, predators must overcome the defenses of their prey. Juvenile eastern oysters (Crassostrea virginica) respond to predator cues by developing harder shells, yet the extent to which these morphological changes influence predator foraging behavior remains unclear. We examined how exposure to predator cues affected the foraging decisions of the southern oyster drill (Stramonita haemastoma), a key predator and aquaculture pest. Oysters reared in the presence of blue crab (Callinectes sapidus) cues developed a more predator-resistant morphology, characterized by shells that were 19 % smaller and 26 % harder than controls. Although drills handled both control and predator-exposed oysters at similar rates, they successfully consumed control oysters twice as often. These results suggest that drills do not discriminate between oyster morphologies from a distance but instead rely on mechanical feedback during handling to guide their foraging choices.