Meeting Abstract

80.6  Wednesday, Jan. 6  Horn possession does not appear to limit natural flight performance in the giant rhinoceros beetle Allomyrina dichotoma MCCULLOUGH, E.L.; University of Montana mccullough.e@gmail.com

Sexually selected characters are assumed to be costly to produce and maintain, and individuals are expected to reduce the magnitude of these costs whenever possible through morphological and/or behavioral modifications. In the giant rhinoceros beetle Allomyrina dichotoma, males have a long, branched head horn that they use in male-male competitions over access to resources where hornless females feed and mate. Males with longer horns are more likely to win these comtests and thereby gain fertilization opportunities. However, the cost of bearing horns has not been elucidated. Males sometimes fly long distances to feeding sites, and flight performance is likely to be critically challenged in males with long, heavy horns. As a first step in identifying possible flight costs in this species, I tested whether the presence of a horn and/or differences in horn size affected natural flight behavior. I used radio telemetry and scan samples to measure how far large-horned males, short-horned males, and hornless females traveled each night, and a radar gun to measure normal flight speeds. I predicted that long-horned males would fly shorter distances and at slower speeds than short-horned males or females due to the increased mass and aerodynamic drag imposed by the elaborate horns. Surprisingly, I found no relationship between flight speed and size or between flight distances and size, which suggests that, at least in this species, horns do not appear to limit flight performance in the field. Future research will focus on determining the specific energetic and aerodynamic costs of flight in this species, whether these costs differ among long-horned males, short-horned males, and hornless females, and if individuals can ameliorate these costs through morphological and/or behavioral modifications.