UC San Diego

Animals constantly make decisions as they carry out basic functioning. Assessment of available options is facilitated by information obtained by directly sampling the environment (personal information) or by monitoring others' behavior (social information). Social information use appears widespread, and has important ecological and evolutionary effects. This may be particularly true for eavesdropping, exploitation of evolved signals that are aimed at other individuals This dissertation addresses the roles of two types of social information by foraging stingless bees (Hymenoptera: Apidae, Meliponini) : conspecific "footprints" and heterospecific recruitment pheromones. Stingless bees are a large group of highly eusocial bees that are major tropical pollinators. Across species, they exhibit high diversity in colony sizes, foraging strategies, resource recruitment mechanisms, body sizes, and aggressiveness. In Chapter 1, I show that Melipona quadrifasciata responds to social information from nestmates, showing attraction to previously visited locations. Chapter 2 finds that group-foraging species, which typically have large colonies, dominate individual resources and reduce feeding opportunities for solitary- foraging species. I then use the dominance relationships determined in Chapter 2 to study eavesdropping between a dominant-subordinate species pair: Trigona hyalinataand Trigona spinipes. In Chapter 3 I show that recruitment pheromone chemistry for the two species is distinct but overlapping, and that eavesdropping responses do not match the predicted pattern. Rather than show attraction to subordinate's pheromone, T. hyalinataavoided full-strength pheromone. Trigona spinipeswas expected to avoid T. hyalinatapheromone, but instead showed little response. Chapter 4 expands on this work, investigating whether perceived costs determine eavesdropping responses. Consistent with this, T. hyalinataexhibited a concentration-dependent response to T. spinipespheromone. Economic modeling confirmed that decision-making based on perceived takeover costs matches empirically-determined eavesdropping responses. This model highlights the role of dominance in predicting a species' optimal eavesdropping behavior, and degree of sensitivity to energetic constraints. I provide the first detailed assessment of intra-guild social information use by a non-vertebrate, significantly improving understanding of eavesdropping within a trophic level. This work highlights that options' costs can drive decision-making even for animals with relatively simple brains. I also demonstrate the utility of economic decision analysis models for behavioral ecology