image: Moths are a mainstay food source for bats, which use echolocation to hunt their prey. Scientists are studying how moths have evolved passive defenses over millions of years to resist their primary predators. While some moths have evolved ears that detect the ultrasonic calls of bats, many types of moths remain deaf. In those moths, researchers have found that the insects developed types of "stealth coating" that serve as acoustic camouflage to evade hungry bats. Neil will describe his work during the Acoustical Society of America's 176th Meeting, Nov. 5-9. This image shows a Cabbage tree emperor moth (Bunaea alcinoe), one of the species used in Thomas Neil's research. view more
Credit: Thomas Neil
WASHINGTON, D.C., November 6, 2018 -- Moths are a mainstay food source for bats, which use echolocation (biological sonar) to hunt their prey. Scientists such as Thomas Neil, from the University of Bristol in the U.K., are studying how moths have evolved passive defenses over millions of years to resist their primary predators.
While some moths have evolved ears that detect the ultrasonic calls of bats, many types of moths remain deaf. In those moths, Neil has found that the insects developed types of "stealth coating" that serve as acoustic camouflage to evade hungry bats.
Neil will describe his work during the Acoustical Society of America's 176th Meeting, held in conjunction with the Canadian Acoustical Association's 2018 Acoustics Week, Nov. 5-9 at the Victoria Conference Centre in Victoria, Canada.
In his presentation, Neil will focus on how fur on a moth's thorax and wing joints provide acoustic stealth by reducing the echoes of these body parts from bat calls.
"Thoracic fur provides substantial acoustic stealth at all ecologically relevant ultrasonic frequencies," said Neil, a researcher at Bristol University. "The thorax fur of moths acts as a lightweight porous sound absorber, facilitating acoustic camouflage and offering a significant survival advantage against bats." Removing the fur from the moth's thorax increased its detection risk by as much as 38 percent.
Neil used acoustic tomography to quantify echo strength in the spatial and frequency domains of two deaf moth species that are subject to bat predation and two butterfly species that are not.
In comparing the effects of removing thorax fur from insects that serve as food for bats to those that don't, Neil's research team found that thoracic fur determines acoustic camouflage of moths but not butterflies.
"We found that the fur on moths was both thicker and denser than that of the butterflies, and these parameters seem to be linked with the absorptive performance of their respective furs," Neil said. "The thorax fur of the moths was able to absorb up to 85 percent of the impinging sound energy. The maximum absorption we found in butterflies was just 20 percent."
Neil's research could contribute to the development of biomimetic materials for ultrathin sound absorbers and other noise-control devices.
"Moth fur is thin and lightweight," said Neil, "and acts as a broadband and multidirectional ultrasound absorber that is on par with the performance of current porous sound-absorbing foams."
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Presentation #2aAB9, "Stealthy moths avoid bats with acoustic camouflage," by Thomas R. Neil, Zhiyuan Shen, Bruce W. Drinkwater, Daniel Robert and Marc W. Holderied will be Tuesday, Nov. 6, 11:15 a.m. in the SHAUGHNESSY (FE) room of the Victoria Conference Center in Victoria, British Columbia, Canada.
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WORLD WIDE PRESS ROOM
In the coming weeks, ASA's World Wide Press Room will be updated with additional tips on dozens of newsworthy stories and with lay language papers, which are 300-800 word summaries of presentations written by scientists for a general audience and accompanied by photos, audio, and video. You can visit the site, beginning in late October, at http://acoustics.org/world-wide-press-room/.
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LIVE MEDIA WEBCAST
A press briefing featuring a selection of newsworthy research will be webcast live from the conference Tuesday, Nov. 6, 2018. Times and topics to be announced. Members of the media should register in advance at http://aipwebcasting.com.
ABOUT ASA
The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world's leading journal on acoustics), Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. For more information about ASA, visit https://acousticalsociety.org.
ABOUT CAA
The Canadian Acoustical Association (CAA) is a professional, interdisciplinary organization that fosters communication among people working in all areas of acoustics in Canada; promotes the growth and practical application of knowledge in acoustics; encourages education, research, protection of the environment, and employment in acoustics; and is an umbrella organization through which general issues in education, employment and research can be addressed at a national and multidisciplinary level. For more information about CAA, visit http://caa-aca.ca.