Metabolic incentives for dishonest signals of strength in the fiddler crab Uca vomeris

To reduce the potential costs of combat, animals may rely upon signals to resolve territorial disputes. Signals also provide a means for individuals to appear better than they actually are, deceiving opponents and gaining access to resources that would otherwise be unattainable. However, other than resource gains, incentives for dishonest signalling remain unexplored. In this study, we tested the idea that unreliable signallers pay lower metabolic costs for their signals, and that energetic savings could represent an incentive for cheating. We focused on two-toned fiddler crabs (Uca vomeris), a species that frequently uses its enlarged claws as signals of dominance to opponents. Previously, we found that regenerated U. vomeris claws are often large but weak (i.e. unreliable). Here, we found that the original claws of male U. vomeris consumed 43% more oxygen than weaker, regenerated claws, suggesting that muscle quantity drives variation in metabolic costs. Therefore, it seems that metabolic savings could provide a powerful incentive for dishonesty within fiddler crabs.