Montana Public Radio

Bug Bytes: Dogbane Tiger Moths And Bats

Jun 12, 2020

On summer evenings, when darkness falls and most winged predators have called it quits for the day, bats awaken from their daytime slumber to rule the skies.

Despite darkness, thanks to their ability to echolocate – creating ultrasonic clicks and listening to the echoes that return – bats can create detailed images of their surroundings…including whatever tasty insects might be in their flight path.

Well, most insects, that is. Certain species of tiger moths have developed an effective way to avoid becoming a bat’s next meal. And perhaps none have been studied more than the dogbane tiger moth.

A cycnia tenera moth, commonly known as a dogbane tiger moth.
Credit Glenn Marangelo

These moths have evolved special ears that are sensitive to the echolocation call frequencies used by bats. When the sound of an attacking bat is detected, the moth responds with ultrasonic clicks of its own, created by special vibrating membranes on their abdomens called “tymbals.” The result? The majority of the moths live to fly another night.

Studies revealed several possibilities as to why the moth’s clicks are so effective. Since dogbane tiger moths are toxic and distasteful to bats, the clicks could be a warning signal telling bats, “Don’t eat me. I taste bad.” But further research discounted the likelihood of this hypothesis.

Most likely, the moth’s clicks appear to jam the bat’s echolocation, throwing off their ability to accurately see the potential meal and significantly decreasing their hunting success. When researchers removed the moth’s tymbals and ability to make their own clicks, the vast majority of moths were captured.

This is an amazing example of how life has evolved around the age-old interplay of predator and prey. Who knows what other stories are waiting to be told?