Optimal Foraging for Complementary Resources

Abstract

Foraging for complementary resources is widespread in nature. The conventional approaches to optimal foraging are inadequate to describe this phenomenon, since they are predicated on perfect substitution among alternative foods in terms of energy yield per unit time. A more qualitative modeling approach derived from economics is proposed to take explicitly into account the degree of resource substitutability for predators requiring balanced diets. The model yields hypotheses that differ markedly from those derived under the assumptions of perfect resource substitution. First, prey species cannot be ranked (ordinally or cardinally) in terms of their value to predators, since the benefits derived from consumption of one prey type depend on the quantities of complementary resources consumed. Second, prey selectivity is affected by the relative abundance of any potential food source. Third, when food resources are complementary predator fitness is greater on mixed diets than on single species diets.