The benefit of being a social butterfly

Gregarious roosting in Heliconius butterflies was examined in Panama and Costa Rica in 2010 and 2011. These brightly colored, highly toxic neotropical butterflies repeatedly form aggregations in their home range to roost for the night. This behavior has been hypothesized to confer two adaptive functions: information-sharing and/or anti-predator defense. The information-sharing hypothesis was addressed by examining following behavior by butterflies in natural aggregations. The results showed no evidence of roost-mates following one another, therefore rejecting the information-sharing hypothesis. The anti-predator hypothesis was tested using artificial butterfly models of Heliconius erato placed singly and in aggregations in the forest. A significant difference in predation attempts was found between gregarious and solitary roosting butterflies. A significantly higher number of predation attempts was observed on solitary models versus models in aggregations, suggesting that gregarious roosting confers an anti-predatory benefit. This is likely due to collective aposematism in which aggregations of conspicuous, toxic prey communicate a more effective repel signal against predators.