Dispersed Versus Central-Place Foraging: Intra- and Intercolonial Competition in the Strategy of Trunk Trail Arrangement of a Harvester Ant

Abstract

Competition for resources has a clear expression in the spatial arrangement of intensive foraging structures of ants. Trunk trails of harvester ants have been considered as devices that avoid competition between neighboring colonies, which give rise to irregular foraging territories around the nests. This hypothesis is valid for strict central-place foragers but loses strength when the colonies have several nest entrances and approach a dispersed central-place strategy. The strategies of trunk trail allocation in a harvester ant species (Messor barbarus) with both trunk trails and multiple nest entrances are studied in order to ascertain the outcome of the oppositing forces of neighborhood competition and trail arrangement within the colonies. Evidence is found of inter- and intracolonial competitive interactions in the arrangement of trunk trails in this species. Intracolonial competition seems to be superimposed on intercolonial interactions, which generates a composite pattern of trail allocation in which dispersed and central-place foraging concur.