Individual plasticity in alternative reproductive tactics declines with social experience in male guppies

Understanding causes and consequences of behavioural plasticity is a major focus in animal behaviour studies for its importance to any population's ability to persist under changing environments. However, behavioural plasticity in traits linked to reproduction has received surprisingly limited attention, especially in species exhibiting alternative reproductive tactics (ARTs). In this study, we explored how behavioural plasticity in ARTs varies in response to social conditions in male guppies, Poecilia reticulata, an internally fertilizing fish in which males can switch between two ARTs to achieve matings. Males can either court receptive females using elaborate mating displays (courtship), or attempt forced copulations without prior display or female cooperation (sneaking). Although males have a genetic predisposition to engage predominantly in one tactic over the other, the extent to which social experience shapes individual plasticity in these tactics is unknown. We observed that between-individual variation in mating effort and preferred ARTs was repeatable over time and largely explained by variation in body size and coloration between individuals. Moreover, we showed experimentally that males exposed to social cues rapidly developed a preference towards either sneaking or courting, resulting in a rapid decline in individual plasticity compared to their socially deprived counterparts. These findings accord with the theoretical predictions that behavioural plasticity should decline as individuals incrementally adjust to local environmental conditions and, thus, when environmental uncertainty is reduced.