Newspaper article The Christian Science Monitor

How Hawkmoths Jam the Sonar Signals from Bats

Newspaper article The Christian Science Monitor

How Hawkmoths Jam the Sonar Signals from Bats

Article excerpt

In the dark caves and jungles of the world, there's an epic 65- million-year evolutionary battle going on between bats and moths.

Moths are obviously the underdogs. But scientists are learning that moths have found ingenious ways to counter the weapons of the bat.

The latest discovery is that the hawkmoths may be jamming the sonar signals bats use to track and catch moths in flight. How do they do it?

According to an article in Nature, behavioral ecologist Jesse Barber of Boise State University in Idaho and phylogeneticist Akito Kawahara of the University of Florida in Gainesville went to Borneo to study how hawkmoths defend themselves.

"When the researchers played bat ultrasound to the hawkmoths, they found that three species (Cechenena lineosa, Theretra boisduvalii and Theretra nessus) they had captured emitted ultrasound clicks in response. The males did so by rapidly grating stiff scales on the outer surface of their 'claspers' -- structures normally used to grab females during mating -- against part of the abdomen, the researchers report. Females also seem to pull part of their genitalia inwards so that genital scales rub against their abdomens."

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This is the second species of moth known to man to find a way to jam the echolocation system employed by bats.

In a 2009 article in the Scientific American, Aaron Corcoran, a biology PhD student at Wake Forest University and the lead author of the paper about how tiger moths jam bat sonar, described how scientists studied and tested behavior of the Bertholdia trigona against the big brown bat Eptesicus fuscus, using high-speed infrared cameras and an ultrasonic microphone to record the action over nine consecutive nights.

"Normally, a bat attack starts with relatively intermittent sounds. They then increase in frequency--up to 200 cries per second- -as the bat gets closer to the moth "so it knows where the moth is at that critical moment," Corcoran explains. But his research showed that just as bats were increasing their click frequency, moths "turn on sound production full blast," clicking at a rate of up to 4,500 times a second. This furious clicking by the moths reversed the bats' pattern--the frequency of bat sonar decreased, rather than increased, as it approached its prey, suggesting that it lost its target. …

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