Keeping track of changes: the performance of ant colonies in dynamic environments

Animals living in dynamic foraging environments are subject to trade-offs between exploiting current resources and exploring alternative resources. Social insects face the additional challenge of redistributing an often large foraging force among multiple patches in the absence of leadership or centralized control. We used comparative, field-based techniques to study the dynamic performance of five ant species. We also investigated how the number of ants involved in the decision-making process influenced feeder exploitation and dynamic performance. Colonies were offered two feeders that differed in quality. After 30 min, the feeders changed quality; the challenge for the colonies was to reallocate foraging effort following the swap. We predicted that colonies that invested heavily in exploiting the high-quality resource would have difficulty reallocating foragers following the quality swap. We also predicted that larger foraging groups would have stronger exploitation intensity and better dynamic performance than smaller groups. Overall, we found evidence for a trade-off between exploitation and flexibility such that species that tended to focus strongly on high-quality resources had relatively poor dynamic performance. Contrary to our prediction, we found no evidence that the number of ants influenced dynamic performance. The number of ants did, however, influence exploitation intensity such that colonies with fewer foragers tended to allocate a greater proportion of ants to the higher quality feeder than larger colonies. Our results highlight the factors that influence how species respond to the exploration–exploitation trade-off when faced with short-term fluctuations in the foraging environment.