Behavioural mechanisms of prey selection in crabs

Laboratory experiments were designed to investigate key stimuli used by blue crabs, Callinectes sapidus, when selecting prey. Results were compared with behaviour predicted, or assumed, by optimal foraging theory. Both live prey and simple models were employed to monitor the responses of blue crabs foraging either in tactile mode, as when feeding on marsh mussels, Geukensia demissa, attached to the substratum, or in visual mode, as when foraging on fiddler crabs, Uca spp., moving over the substratum. We suggest that foraging blue crabs simply respond to the strongest stimuli received from the prey. Items are rejected after a certain persistence time if the attack is proving unsuccessful. Persistence time is adjusted, through experience, to expectations of local prey quality or availability. The integrated result of this key-stimulus mechanism of prey selection will be a close match to diets predicted by other behavioural models, including that based on optimal foraging theory.