The effects of familiarity on escape responses in the Trinidadian guppy (Poecilia reticulata)

Predation is the main driver of mortality during early life stages. The ability to avoid and evade potential threats is, therefore, favoured to evolve during the early stages of life. It is also during these early stages that the process of familiarization occurs. It has long been recognized that associating with familiar individuals confers anti predator benefits. Less, however, is known about how predator evasion is affected by social experience during early stages. In this study we test the hypothesis that familiarization acquired during early life stages improves anti predator escape responses. Using the Trinidadian guppy we examine the effect of different early social conditions in the three main components of predator evasion. Using high-speed motion analysis we compared the responsiveness, reactive distance and magnitude of the response (maximum speed, maximum acceleration and distance) of the response to a visual stimulus in groups composed either of familiar or non-familiar individuals. Surprisingly, groups composed by familiar individuals were less responsive than groups of unfamiliar individuals. It is plausible that familiarity equips individuals with better skills to accurately assess the threat avoiding false alarms. Reactive distance and magnitude of response were more dependent on individual size than on familiarity. Larger individuals reached higher maximum speeds and total distances in their escape response. Our approach allowed us to tease apart which aspects of an escape response are more likely to be influenced by early social conditions.