Increased survival as a function of interactions with experienced partners

The evolution of group-living has been at the heart of behavioral ecology, since the inception of this discipline in the mid 1960's. Here, we provide the first evidence for a direct fitness benefit accrued when an individual is paired with a conspecific that has recently interacted with a predator. Male guppies have a significantly higher probability of surviving encounters with a predator when paired with a partner that has survived a recent encounter with a predator versus a predator-naive partner (chi(2) = 7.43, df = 1, P = 0.006). Furthermore, guppies prefer to associate with conspecifics that have recently encountered predators over inexperienced partners (one-tailed binomial test, P = 0.026). Increased survival as a function of interactions with partners that have survived an encounter with a predator, coupled with a preference for such partners, adds a new and important component to the benefits of living in social groups.