Nutrient-specific compensation following diapause in a predator: implications for intraguild predation.

In recent years it has become clear that intraguild predation (where predators feed on other predators) has important consequences for food webs, and yet very little is known about its nutritional or functional bases. In the most detailed study of the nutritional basis of foraging by a predator to date, we used geometrical analysis to test the ability of the generalist invertebrate predatory beetle, Agonum dorsale (Carabidae), to forage selectively for lipid and protein over a 10-day period following emergence from winter diapause, and we measured associated changes in body lipid and nitrogen content. Over the first 48 hours, beetles that were offered two nutritionally imbalanced but complementary foods self-selected a diet high in lipids, and thereafter the proportion of protein in the selected diet increased.