Structural adaptations to diverse fighting styles in sexually selected weapons

Animal weapons are among nature's most diverse structures. Intuitively, species have different types of weapons because they fight in different ways, yet no studies have directly tested whether weapons perform better at the animals' own style of fighting than they do at others. We constructed biomechanical models of the horns of different rhinoceros beetle species to evaluate the functional performance of horns in response to both species-typical and species-atypical fighting loads. We found that horns are both stronger and stiffer in response to species-typical fighting loads, which suggests selection for improved performance under different fighting styles played an important role in the diversification of weapon form.