Risk-taking behavior predicts aggression and mating success in a fiddler crab

Evidence is growing that an individual's propensity to take risks in the presence of a predator is correlated to behaviors that can affect individual fitness. We examined whether risk-taking behavior predicts aggression, surface activity levels, and mating success in male fiddler crabs, Uca mjoebergi. Risk-taking behavior was highly consistent among individuals, remained stable over time, and was unrelated to male size. We found that males that took greater risks in the presence of a potential predator also behaved more aggressively when searching for a new territory. In addition, bold males exhibited higher surface activity levels and spent more time courting females compared with their shy counterparts. Although risk-taking behavior was independent of other sexually selected traits, it accurately predicted male mating success in U. mjoebergi. We suggest nonsexually selected traits, such as risk taking, may represent important behavioral predictors of success in other species.