Predation and the Flight, Morphology, and Temperature of Neotropical Rain-Forest Butterflies

Abstract

The morphological traits, flight speeds, and temperatures of 54 species of common Neotropical rain-forest butterflies in Corcovado National Park, Costa Rica, correlate with their palatabilities. Butterfly palatabilities were determined in feeding experiments according to the responses of a local specialized insectivorous bird, the rufous-tailed jacamar (Galbula ruficauda melanogenia). Among 12 morphological traits examined, body shape (ratio of body length to thoracic width) correlates most closely with flight and temperature measures of butterflies and with the responses of jacamars. In general, palatable butterflies have relatively wider thoraxes and shorter bodies, and they fly faster and more irregularly. They show higher thoracic temperatures and are active in higher ambient temperatures. Although more frequently pursued, palatable butterflies more often escape from the birds' attacks. In contrast, unpalatable butterflies have longer, more slender bodies and fly more slowly and regularly. They are active at lower ambient temperatures, operating with thoracic temperatures nearer to ambient temperatures. The majority of unpalatable butterflies were ignored by the jacamars, but, if pursued, the unpalatable butterflies were more easily captured. In order to enhance the flight speed and acceleration necessary for successful escape, most palatable butterflies have relatively wider thoraxes, indicating that they possess more-massive flight muscles. Their shorter bodies and abdomens, which are often hidden between extended areas of the two hind wings, may help to conserve heat, increase aerodynamic performance, and reduce the chance of being seized by the abdomen. In contrast, unpalatable butterflies and their mimics usually differ from palatable butterflies in appearance and behavior so that potential predators discriminate and reject them on sight. Most unpalatable butterflies fly slowly and regularly, which facilitates their capture by potential predators but ultimately relieves them of maintaining more costly flight mechanisms. These different antipredator strategies adopted by palatable and unpalatable butterflies (escape vs. aposematism) are reflected in an adaptive suite of morphological, flight, and thermal characteristics.