Communal Roosting in Butterflies

When we arrive at MOSI Outside each morning, one of our first jobs is to visit the Flight Encounter and prepare it for daily visitors. This includes watering, deadheading plants, sweeping, and other chores that ensure our exhibit is ready for the museum guests who come to admire and learn more about Florida's native butterflies.

While we perform these chores, the butterflies are just beginning to become active after a night at rest. On particularly cool or cloudy mornings, we'll find many butterflies still resting, waiting for the sun to rise. Most rest under leaves, hanging upside-down, though others are found at the top of the encounter hanging from the screen. Some rest singly, but certain species of butterflies are nearly always to be founding resting in groups, often in the same places. This butterfly behavior is called "roosting", and is most often practiced by butterflies of the Heliconius genus, including the Zebra Longwings (Heliconius charithonia) and Julia Longwings (Dryas iulia) commonly found in our exhibit.

Studies on the Heliconias have indicated that the most likely reason for this communal roosting behavior is defense. Using detailed models, Susan Finkbeiner experimented with these butterflies in Costa Rica. She and her team observed that when a single butterfly rested alone, it was three times more likely to be attacked by birds than when five or more butterflies rested together. You can read her entire paper here.