SRYGLEY, R.B.; Smithsonian & Seoul National University: Locomotor mimicry and energetic costs of aposematic signaling in butterflies

Bates hypothesized that some butterfly species that are palatable gain protection from predators by appearing similar to distasteful butterflies. When undisturbed, distasteful butterflies fly slowly and in a straight line, and palatable, Batesian mimics also adopt this nonchalant behavior. When seized by predators, distasteful butterflies are defended by toxic or nauseous chemicals. Lacking chemical defenses, Batesian mimics depend on flight to escape attacks. Previously, I demonstrated that distasteful, passion-vine butterflies that mimic one another in coloration also mimic one another in locomotion. Here I compare the flight biomechanics of the tiger mimics in the subfamilies Pierinae, Ithomiinae, and Danainae and confirm that aerodynamic power requirements are similar among distasteful, M�llerian mimics. This similarity in power requirements extends to the palatable, Batesian mimics. Flight in warning-colored mimetic butterflies and their distasteful models is more costly than closely-related, non-mimetic butterflies. The increased cost is due to differences in both wing shape and kinematics. Batesian mimics and their models slow the angular velocity of their wings to enhance the color signal but at an aerodynamic cost. Moreover, the design for flight in Batesian mimics has an additional energetic cost over that of its models. The additional cost of Batesian mimicry is empirical support for the theoretically well-founded handicap principle of animal communication. The added cost may cause Batesian mimics to be rare, explaining a general pattern that Bates first observed.