Harvesting resources in groups or alone: the case of renewing patches

Group foraging has been proposed to be the most efficient manner with which to exploit habitats with renewing patches as individuals in groups are less likely to revisit patches that have already been exploited recently by others. However, to avoid a group-selection argument, it is necessary to compare the success of solitary and group foraging tactics when each competes with the other. We used a genetic algorithm approach to examine the costs and benefits of exploiting renewing resources in a spatially and temporally explicit habitat, thus controlling the time course of resource renewal and including the time cost of traveling between patches, which may be a significant factor for group foragers that deplete patches more quickly. Results indicate that group foragers fare more poorly than an equivalent number of solitary foragers in the same habitat unless the rate of resource renewal is very low. The low revisitation rate by group foragers allows resources to replenish more fully, thus maintaining the resource level across the habitat at a higher level. In contrast, solitary foragers, who revisit previously exploited patches more often, maintain the same resources at a lower level. Nevertheless, a pure population of group foragers can be readily invaded by solitary foragers even when the rate of renewal is at low levels. We conclude that while group foraging may be an efficient tactic to exploit renewing resources, it is not a stable strategy under the circumstances examined in this model. Copyright 2005.