Newswise — To avoid becoming a bat’s tasty treat, a species of tiger moth plays a trick with sound. The moth can make up to 450 ultrasonic clicks in a tenth of a second to jam the hungry bat’s sonar and escape death.
The discovery was made by Aaron Corcoran, a Wake Forest University graduate student, and William Conner, professor of biology at Wake Forest.
“This is the first example of prey that jams biological sonar,” Conner says.
Their research documenting the bat vs. moth evolutionary arms race was published in Science. Corcoran will also present his findings at the North American Symposium on Bat Research in November and traveled to Japan to address the Animal Sonar Symposium this summer.
In a series of experiments, Corcoran and Conner observed free-flying big brown bats hunting moths in a sort of “bat cave” set up in the basement of the biology building. High-speed infrared video cameras recorded the interactions between predator and prey. The researchers also recorded the high-frequency sounds made by both the bats and the moths during each interaction.
When a tiger moth hears the sonar pings of a bat in search of prey, it clicks back using a paired set of structures called “tymbals,” Corcoran says. The high-speed, high-frequency clicks disrupt the bat’s echolocation cycle. Although the researchers have yet to discover exactly how the jamming works, the sounds could mask the echoes that the bat uses to locate the moth. Or, it might blur the bat's acoustic image of the moth so the bat can’t determine its exact location.
“Sonar jamming illustrates a new level of escalation in a 50-million-year-old arms race,” Corcoran says.
Now, Corcoran is doing field research to learn more about how the sonar-jamming defense works in the wild. He has found the perfect place to study the ultrasonic battle of bats and moths. In the Chiricahua Mountains of Arizona, one in every three moths is a Bertholdia trigona, the species of moth that uses ultrasonic clicks as a sonar-jamming defense. Many species of bats, including the one they studied in the lab, are also prevalent. He is trying to figure out if the moths are using evasive maneuvering combined with sound to evade capture.
“Are they combining defenses or does sonar jamming work so well that they go along their way without making elaborate loops and spirals to avoid being eaten,” Corcoran says. He would also like to know if the defense that works so well against big brown bats in the lab, will work against other species of bats in the wild.