Foraging Strategy, Worker Mortality, and the Growth of the Colony in Social Insects

Models of optimal foraging often assume that maximizing the long-term net rate of gain is equivalent to maximizing fitness. We present a model that challenges this view on theoretical grounds for foragers from colonies of social insects. To maximize the number of reproductive forms produced by a colony, the production of new workers should be at a maximum during the ergonomic stage of a colony's development. However, when the mortality rate of workers depends on foraging performance, then maximization of the net rate no longer maximizes fitness. Under such conditions, the model predicts deviations from net-rate maximization (gain per unit of time) that may resemble the maximization of efficiency (gain per metabolic expenditure), as found in our earlier studies.