Ultrasound from moth’s genitals blocks bat radar

U. FLORIDA (US) — Hawkmoths produce sonic pulses from their genitals in response to high-frequency sounds from bats.

Researchers suspect the ultrasound is a self-defense mechanism used to jam the echolocation ability of predators.


Ultrasound has only been demonstrated in one other moth group, says study co-author Akito Kawahara, an assistant curatorat the Florida Museum of Natural History at the University of Florida.

“This is just the first step toward understanding a really interesting system. Echolocation research has been focused on porpoises, whales, and dolphins. We know some insects produce the sounds, but this discovery in an unrelated animal making ultrasound, potentially to jam the echolocation of bats, is exciting.”

Hawkmoths are major pollinators and some are agricultural pests. Researchers use the insects as model organisms for genetic research due to their large size.

Previous research shows tiger moths use ultrasound as a defense mechanism. While they produce the sound using tymbals, a vibrating membrane located on the thorax, hawkmoths use a system located in the genitals. Scientists found at least three hawkmoth species produce ultrasonic sound, including females.

Researchers believe hawkmoths may produce the sound as a physical defense, to warn others or to jam the bats’ echolocation, which confuses the predators so they may not identify an object or interpret where it is located, Kawahara says.

Published in the journal Biology Letters, the study was conducted in Malaysia, which has the highest diversity of hawkmoths worldwide. Kawahara also conducted research in the jungles of Borneo and the lower Amazon.

“So much work has been focused on animals that are active during the day, but there are a lot of really interesting things happening at night, and we just don’t know a lot about what is actually going on—because we can’t hear or see it,” Kawahara says.

“The fascinating part is that there are a lot of new discoveries to be made. It’s a totally unknown, unexplored system.”

Researchers used high-energy lamps to capture the hawkmoths in the jungle. Study co-author Jesse Barber and a team from Boise State University played pre-recorded bat sounds to the insects, and all researchers studied their behavior.

With the insects tethered inside an enclosed sound rig containing an ultrasonic microphone and speaker connected to two laptop computers, researchers recorded the sounds the hawkmoths made in response to being touched and hearing the echolocation sounds. The responsive species include Cechenena lineosa, Theretra boisduvalii, and Theretra nessus.

“As a museum, we are creating a library of life,” Kawahara says. “Museum specimens are usually preserved immediately, but we are trying to understand the behavior of these organisms so that we have a record of their behavior along with the specimen and DNA. This is why there are so many interesting things we’re starting to discover.”

Hawkmoths are among the fastest and most proficient flying insects, and there are more than 1,400 species worldwide. Their long proboscis, or mouthpart, makes them important pollinators.

“We think hawkmoths are a primary food source for bats because none appear to be chemically defended, which is why they have evolved anti-bat ultrasound strategies,” Kawahara says.

“Hawkmoths have evolved different ways of avoiding bats—I can’t even explain how amazing the system is; it is just fascinating.”

The National Science Foundation funded the study.

Source: University of Florida