Optimal Foraging: Partial Consumption of Prey

Abstract

Many predators do not consume their prey whole. If these foragers feed on progressively less valuable portions of each prey item, they might maximize their net rate of energy intake by leaving an item while some material still remains, to search for more rewarding portions of another item. Using a graphical approach, increasing prey availability or value and decreasing search and handling costs should decrease the optimal time spent feeding on each item. For a given prey type similar predictions can be made concerning the optimal proportion of each item eaten. That a lower proportion of each item should be eaten when prey densities are higher was confirmed by a laboratory experiment. Acknowledging that many foragers do not consume their prey whole requires a modification of the concepts of a prey item and its value. Prey items should be defined by the forager, not by their spatial boundaries as perceived by an ecologist. An item''s value should be its maximum possible net energy intake per unit handling time rather than the intake rate from consuming an entire item. The predicted foraging patterns should have a stabilizing effect on the predator-prey interaction if partial consumption kills or drastically reduces the fitness of the prey individual.