Bats Invent Butterfly Day-flight

Bats are being credited with "inventing" modern-day butterfly day-flight, according to Carleton University biology post-doctoral student Jayne Yack and University of Toronto at Mississauga zoology professor James Fullard. Their work was reported by Janet Wong, a news services officer with the Department of Public Affairs, Toronto.

The two studied the anatomies and behaviors of day-flying butterflies and ultrasonic hearing in night-flying butterflies. They found that both day- and night-flyers had evolved defense and communication systems to protect against predatory bats."Bats are major predators of night-flying insects, and this research points to the intense pressure on all nocturnal insects to evolve methods of detecting and avoiding insect-eating bats," says co-author Fullard, according to a press release.

"With respect to butterflies, the majority of them switched their activity from night to day, thereby avoiding bats altogether. But for some rare species of nocturnal butterflies, the evolution of ultrasound-sensitive ears means that these insects have developed and been able to use this sensory defense to stay alive during the night."

Yack and Fullard found night-flying butterflies with ears on their wings that detect calls used to locate and track prey. When researchers exposed nocturnal butterflies to simulated ultrasonic stimulus--such as the type emitted by bats-"the insects exhibited bat-evasion flight maneuvers characterized by steep dives, climbs or up or down loops and spirals.

Until now, it was believed that ultrasonic hearing was a common defense and communication mechanism for moths and other nocturnal insects but not butterflies," Wong wrote.

"The discovery of ultrasonic hearing in this species of night-flying butterflies in Panamá is quite remarkable," Wong quotes Fullard as saying. "Clearly, bat predators imposed a great selection pressure on the evolution of ears in this type of butterfly."

By and large, butterflies are predominantly day-flying, say the researchers, according to Wong. It was thought that the daytime behavior of butterflies was enough to protect them from bats. However, day butterflies have evolved highly developed visual systems for communication and to detect other types of predators that hunt during the day, Wong writes.

Batty Web sites
Bat Conservation International and its Links page

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