Intercolony distance predicts the decision to rescue or attack conspecifics in weaver ants

Abstract

Group formation and recognition mechanisms can strongly influence the decision to cooperate or attack in animal societies. Therefore, testing how individuals recognize group membership, and the decision to cooperate or attack during social interactions is critical to understanding the evolution of sociality. We explore decision-making in the weaver ant Oecophylla smaragdina, a highly territorial and also cooperative species. Here, we report a previously undescribed rescue behavior for weaver ants, and determine the role of distance and group membership in residents’ decisions to either rescue or attack conspecifics in distress. First, we tested if residents preferentially rescued nestmates and attacked non-nestmates. Our results show that rescue was more likely for nestmates; however, surprisingly, conspecifics from neighboring colonies were rescued in 43% of the distress trials. Furthermore, attacks became more frequent as distance between colonies increased showing a dear enemy effect, which may be explained by familiarity, odor recognition, and/or relatedness. Our work exploring the factors that influence the decision to rescue or attack provides novel evidence to understand the underlying selective pressures that shape decisions of cooperation or conflict in highly cooperative societies.