Born to win or bred to lose: aggressive and submissive behavioural profiles in crickets

Aggression between conspecific males is widespread in the animal kingdom, as is the fact that some individuals are far more aggressive than others. Consistent interindividual differences in behavioural profiles are generally regarded as a hallmark for animal 'personality' in both vertebrates and invertebrates, but their proximate causes are poorly understood. While the social experiences of winning and losing are known to lead to heightened and depressed aggressiveness, respectively, and that different fighting experiences can lead to changes in other behaviours, the extent to which interindividual variation in aggression and correlated behaviours are determined alone by fighting experience, environmental factors or inherited predisposition is unclear. In this study, we video tracked individual, virgin adult male crickets, Gryllus bimaculatus, to quantify their general motility, exploratory behaviour and attraction to conspecific males after 48 h of social isolation, and compared this with their performances 24 h later, immediately after a fighting tournament that yielded cohorts of aggressive winners and submissive losers. Although all known behavioural effects of previous social experience in crickets last only a few hours at most, we found significant behavioural differences between the 48 h isolated future winners and losers, i.e. before the fight tournament. However, the experiences of winning and losing led to more pronounced and some additional changes in behaviour. We discuss whether these different behavioural profiles associated with the chances of winning and losing ('personalities') could arise from factors other than fighting experience, or possibly from dominance and subjugation experiences gathered under crowded culture conditions before social isolation with cumulative effects that may persist longer than those presently known.