Meeting Abstract
Theory predicts that animals should resolve conflicts safely, yet many animals use potentially dangerous “weapons” during contests. Behavioral and biomechanical studies can reveal the role of weaponry in contest assessment and resolution. We tested hypotheses addressing assessment and resolution in the mantis shrimp Neogonodactylus bredini, which uses raptorial appendages to present visual displays and to deliver high-force strikes during territorial contests. We first tested if displays signaled strike performance and were used to resolve conflicts without dangerous striking. We measured competitor’s appendage morphology and maximum strike force, then analyzed size-matched contest behavior. Morphology did not correlate with force, and 33/34 contests involved striking. While displays did not signal performance to resolve contests, competitors exchanged strikes on each other’s armored tailplates in a behavior we termed “telson sparring”. To test whether telson sparring functions to inflict costs or in assessment of relative ability, we matched contest dynamics to assessment models. Using correlations and a network analysis of behavioral sequences, we found that sparring is used to assess relative ability. Finally, we measured the energetic cost of sparring. We filmed sparring strikes (30-40 kfps), measured strike velocity, and used a biomechanical model to calculate strike potential energy, comparing this to published measures of resting metabolic rate. In preliminary analyses, each sparring strike used ~1% of hourly metabolic rate. Individual differences in the ability to withstand this cost may support honest signaling theory. Overall, these results show how potentially-deadly weapons can function in assessment, suggesting future work on the behavior and biomechanics of weapon use.
