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

Evidence is growing that an individual's propensity to takerisks in the presence of a predator is correlated to behaviorsthat can affect individual fitness. We examined whether risk-takingbehavior predicts aggression, surface activity levels, and matingsuccess in male fiddler crabs, Uca mjoebergi. Risk-taking behaviorwas highly consistent among individuals, remained stable overtime, and was unrelated to male size. We found that males thattook greater risks in the presence of a potential predator alsobehaved more aggressively when searching for a new territory.In addition, bold males exhibited higher surface activity levelsand spent more time courting females compared with their shycounterparts. Although risk-taking behavior was independentof other sexually selected traits, it accurately predicted malemating success in U. mjoebergi. We suggest nonsexually selectedtraits, such as risk taking, may represent important behavioralpredictors of success in other species.