Decision making by small and large house-hunting ant colonies: one size fits all

Abstract

We conducted two experiments with Temnothorax albipennis ant colonies. In the first, we assessed their ability to select the best nest, in terms of entrance size, among an array of mediocre ones. Small and large ant colonies were equally adept at solving this best-of-N choice problem. However, large colonies were faster than small ones at finding the best nest probably because they could deploy more scouts. As a result, large colonies in nature probably find more of the available nests more quickly than small colonies. Thus larger colonies may have a greater tendency to split than small colonies. Large colonies, however, used larger quorum thresholds to make collective decisions than smaller colonies. Higher quorum thresholds should help to reduce splitting by large colonies. Large colonies also used more reverse tandem runs, a process for recruitment of more active participants into emigrations. More reverse tandem runs may help large colonies to reunite if they do split. In a second experiment, large and small colonies had almost identical preferences for nests with a floor area that would ideally accommodate a fully grown colony. Thus, small colonies behaved in a way that seemed to anticipate their future needs, when they would have grown to fill a larger space.