Does defection during predator inspection affect social structure in wild shoals of guppies?

Reciprocal altruism has been proposed as a possible mechanism for the evolution of cooperative behaviour. However, very few investigations have tested predictions of reciprocity in wild animal populations. In the current investigation we simulated defection during predator inspection in a wild population of guppies, Poecilia reticulata. Two experiments were run: the first simulating defection during a single exposure to a predator and the second during multiple exposures to a predator. We then compared subsequent social and cooperative interactions with those observed prior to the treatments. From theory and previous experiments on cooperation and reciprocity, we predicted that defection would result in a reduction in social and cooperative interactions during subsequent predator inspections. However, our experiments did not find any effect of simulated defection(s) on the subsequent social structure, or on patterns of predator inspection behaviour. We discuss the potential reasons for the observed results and suggest future directions for research to address mechanisms underpinning the nature of cooperative interactions during predator inspection.