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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.

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Abstract1. Signals used during male combat are expected to be honest indicators of fighting ability. However, recent studies show that dishonesty in male signalling is more prevalent than previously believed. 2. Here we show that regenerated (leptochelous) claws in male Uca mjoebergi fiddler crabs are not only dishonest signals of two types of whole-organism performance capacities that are likely to be useful during fights (claw closing force and pull-resisting force), but they are also less effective as weapons in situations where males are unable to bluff. 3. Original (brachychelous) male claws are statistically significant predictors (independent of body size) of both closing force and the force required to pull a male out of a tunnel. By contrast, leptochelous claw size does not convey information on those performance capacities following control for body size. 4. Furthermore, claw size affects fighting ability such that leptochelous residents are at a significant competitive disadvantage to brachychelous residents, although claw type does not affect the ability of non-resident males to win fights. 5. This study is among the first to show that male armaments can dishonestly signal performance traits that are likely important for winning fights, and is the first to show evidence for dishonest signalling of multiple components of fighting ability.

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