HANDLING TIMES, PREY SIZE AND SPECIES SELECTION BY CANCER-NOVAEZELANDIAE (JACQUINOT, 1853) FEEDING ON MOLLUSCAN PREY

Handling times, consumption rates, and prey selection of the New Zealand cancrid crab Cancer novaezelandiae Jacquinot were investigated in relation to mollusc prey of different size, species, geometric shape, and anti-predatory adaptations. In the laboratory, male crabs of three size classes (55-65, 80-90 and 105-115 mm carapace width) were offered four mollusc species, bivalves Mytilus edulis aoteanus Powell and Austrovenus stutchburyi Wood, and gastropods Cominella maculosa Martyn and Turbo smaragdus Gmelin. Handling times of C. novaezelandiae increased with prey size, larger crabs requiring less time to open and consume prey than small crabs. Bivalves were opened more quickly than gastropods, although at small shell size differences were negligible. Energy intake increased with crab size, despite crabs of all sizes consuming similar numbers of prey. Energy consumption was higher when feeding on mussels in comparison to whelks. Profitability curves were derived and predictions about optimum prey size and species were tested. When presented with a size range of prey, crabs selected sizes that minimized time spent foraging. However, when presented with different prey species, crabs maximized energy intake by selecting optimum prey species. Results suggest that C. novaezelandiae is capable of exhibiting a flexible foraging behaviour, which may allow crabs to maximize feeding efficiency. © 1990.