Life-history strategies of optimal foragers

Abstract

The optimal life histories are examined for models in which the average life-history strategy adopted by the population affects the costs and benefits of any individual's strategy. The situation modeled is one in which organisms can gain energy to be used in reproduction by foraging, but in doing so, they expose themselves to increased mortality; thus the proportion of time spent foraging can be used to measure reproductive effort. Simple models of a demographically homogeneous population are used to reexamine questions which have been studied previously using other models. The effects upon optimal reproductive effort of the following factors are examined: increased births per unit effort, increased mortality, and variability in population parameters. In addition, the questions of whether optimal reproductive effort maximizes population size and whether there can be multiple alternative life histories are examined. Results in most cases differ significantly from those of previous studies. No generalizations emerge regarding the effects of the three factors listed above. Optimal life histories in this model generally do not maximize population size. It is possible to have globally stable alternative life histories. It is concluded that frequency dependence will often be important in determining optimal life histories.