DISPERSED VERSUS CENTRAL-PLACE FORAGING - INTRACOLONIAL AND INTERCOLONIAL COMPETITION IN THE STRATEGY OF TRUNK TRAIL ARRANGEMENT OF A HARVESTER ANT

Competition for resources has a clear expression in the spatial arrang ement of intensive foraging structures of ants. Trunk trails of harves ter ants have been considered as devices that avoid competition betwee n neighboring colonies, which give rise to irregular foraging territor ies around the nests. This hypothesis is valid for strict central-plac e foragers but loses strength when the colonies have several nest entr ances 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 ord er to ascertain the outcome of the oppositing forces of neighborhood c ompetition and trail arrangement within the colonies. Evidence is foun d of inter- and intracolonial competitive interactions in the arrangem ent of trunk trails in this species. Intracolonial competition seems t o be superimposed on intercolonial interactions, which generates a com posite pattern of trail allocation in which dispersed and central-plac e foraging concur.