Effects of experience on crab foraging in a mobile and a sedentary species

The effects of experience on prey and prey-patch choice were compared between two species of marine predatory crabs. The blue crab, Callinectes sapidus Rathbun, is highly mobile and forages in a variety of estuarine and lagoonal habitats. The Atlantic mud crab, Panopeus herbstii H. Milne-Edwards, is smaller and less mobile and is found mostly in oyster reefs and on shelly bottoms. In the laboratory, crabs were offered a choice between two prey types (juvenile hard clams, Mercenaria mercenaria Linne, and juvenile oysters, Crassostrea virginica Gmelin) following a preliminary phase in which crabs were trained to feed on clams only, oysters only or a mixture of the two prey types. In field enclosures, crabs were offered a choice between patches of juvenile hard clams located in an inter-tidal salt marsh and in an adjacent unvegetated inter-tidal flat after they were trained to feed in either one of the two habitat types. Both in the laboratory prey-choice and the field prey-patch choice experiments, blue crabs modified their foraging behaviour depending on previous experience. The effect of experience on their foraging behaviour did not diminish after 24 hours. Experience had no significant effects on the foraging behaviour of mud crabs. Differences in the ecological contexts (e.g. in the variability of prey quality and availability) in which the two species forage may explain the greater effect of experience on the blue crab foraging behaviour, although alternative explanations cannot be ruled out.