Boldness is influenced by social context in threespine sticklebacks (Gasterosteus aculeatus)

Boldness refers to the extent to which animals balance risk against benefits when engaging in such behaviors as foraging, exploration or resource competition. Evidence suggests that individuals can behave strategically, acting boldly in situations when doing so is adaptive, whilst avoiding risk when the rewards are correspondingly lower. In this study we sought to determine the effects of social context upon the boldness of threespine sticklebacks (Gasterosteus aculeatus). We found that when individuals were tested alone, those that were more active were more likely to resume foraging sooner when subjected to a simulated predator attack in a separate test, and also consumed more prey in foraging competition trials. We found no effect of group size upon the relative ability of individuals to effectively compete for prey. Group size did affect other behaviours however: focal fish were more active and resumed foraging more rapidly when tested in groups that they did when tested alone. Finally, individual social information use was not correlated with behaviour in other contexts. Two competing hypotheses, the adaptation and the constraint hypotheses have been posited to explain the presence and prevalence of individual variation in boldness; our findings offer partial support for the former of these.