Energetic and aerodynamic costs of rhinoceros beetle horns

My PhD research focuses on the functional costs of weapons, and specifically the costs of flying with elaborate horns in rhinoceros beetles. I plan to characterize the aerodynamic and metabolic costs of flying with exaggerated horns, to examine potential trade-offs associated with these weapons within rhinoceros beetle species, and to compare the aerodynamic costs of horns among species with dramatically different morphologies. My goal is to understand how selective pressures among individuals to minimize the costs of flight may have shaped the behavior, morphology, and flight performance of rhinoceros beetles, and how selective pressures among species living in different habitats and experiencing different ecological constraints may have contributed to the diversification of weapon form.

The primary species that I study is Allomyrina dichotoma, a large rhinoceros beetle that is common throughout Japan, Korea, China, and Taiwan. Males have a long, branched head horn and a short thoracic horn that they use to fight with other males over access to sap sites on the trunks Fraxinus trees where females feed and mate.

During the summer of 2009, I spent ten weeks in central Taiwan observing the natural flight behavior of A. dichotoma in their natural habitat. Specifically, I was interested in measuring how far and how fast beetles fly, and whether or not large-horned males, small-horned males, and females fly different distances or at different speeds. Future research will focus on the specific metabolic and energetic costs of flight, and determining whether these costs differ among large-horned males, small-horned males, and hornless females.

Click below to see a high-speed video of a tethered beetle flying in the lab and a beetle trying to take off in the field!