Effects of Azteca trigona alarm pheromones on heterospecific ant behavior

Animals communicate with each other using a variety of signal modalities, any of which can provide useful information to non-intended receivers, or eavesdroppers. Eavesdropping on chemical signals is a widespread phenomenon but its role in shaping the behavior of multi-species assemblages is poorly known. Here, we tested the hypothesis that workers of multiple Neotropical ant species change their behaviors when exposed to odors of the common canopy ant, Azteca trigona. We exposed workers of 16 canopy ant species (five subfamilies) to A. trigona alarm pheromones and compared their behavioral responses to the behavior of ants in control treatments (ambient air). Seven species showed distinct responses to A. trigona odors relative to the control. The most common behavioral responses were increased antennation and running. The results of this study suggest that eavesdropping on heterospecific alarm signals allows ants to avoid generalized threats or negative interactions with aggressive A. trigona workers. Such eavesdropping presumably is selectively advantageous and may determine local arboreal ant species distributions and interspecific differences in access to resources in the forest canopy.