Variation in foraging behaviour among individuals and populations of dogwhelks, Nucella lapillus: natural constraints on energy intake

Dogwhelks fed upon mussels Mytilus edulis or barnacles Semibalanus balanoides. Diets comprised largely of mussels included fewer, larger prey and provided a greater energy intake than diets comprised largely of barnacles. Dogwhelks feeding on barnacles spent a greater proportion of time foraging and were more likely to engage in extended bouts of sequential attacks. Larger dogwhelks tended to include a greater proportion of mussels in their diet and to take more, larger prey of either type, resulting in greater energy intake. Larger dogwhelks were also more likely to engage in longer foraging bouts. Differences in time-budgets between individuals taking smaller, less profitable prey and those taking larger, more profitable prey are consistent with the idea of a digestion-rate constraint or the maximization of absorption rate, given an optimal rate of gut procesing. Further reduction in the time spent foraging is due to sheltering in refuges during harsh conditions. Dogwhelks thus appear to be able to integrate chracteristics of their internal state with those of the environment (prey availability and mortality risk) when making foraging decisions. -from Authors