The Relevance of Flash Coloration Against Avian Predation in a <i>Morpho</i> Butterfly: A Field Experiment in a Tropical Rainforest

ABSTRACT The flash coloration hypothesis postulates that otherwise cryptically colored animals suddenly displaying conspicuous colors during movement confuse predators, reducing capture. Morpho helenor butterflies have contrasting colors on dorsal (iridescent blue) and ventral (brown) wing surfaces, resulting in sequential blue “flashes” during flight. We tested whether this flashing pattern reduces avian predation on M . helenor in Atlantic rainforest by changing the flashing effect in three experiments. In Experiment 1, we added a blue band to the ventral wing. In Experiment 2, we covered the dorsal wing's blue band with a brown band. Control groups in each experiment were painted such that wing color patterns remained unaltered. Survivorship was evaluated through mark‐recapture censuses and beak marks on the wings. Results show that survivorship of treated butterflies in Experiment 1 decrease markedly compared to unaltered control individuals, while survivorship of treated butterflies in Experiment 2 did not differ compared to control individuals. In Experiment 3, we detected scant predation on treated (blue band added to ventral wing) and control butterflies (brown band added to ventral wing) on the forest floor (wings closed), corroborating that flash coloration is an important protective mechanism during flight. Our field experiments provide the first evidence, to our knowledge, that flash coloration in bright blue Morpho butterflies is an effective defense mechanism against avian predators in a tropical rainforest.