Sonar Jamming

Some moths may use high frequency acoustic signals to warn bats of their potential toxicity and thus deter depredation.

Acoustic warning signals emitted by tiger moths (Barsine cuneonotatus) were found in laboratory experiments to deter bat predation. That behavior has now been shown to occur in nature and is used as a defense mechanism. Field research conducted at Wake Forest University on free-flying bats in their natural habitats shows that tiger moths of two species (Pygarctia roseicapitis, the Red-headed Pygarctia Moth and Cisthene martini, the Lichen Moth) produce ultrasonic signals to warn bats they don’t taste good (a form of sonar jamming?). Biology graduate student Nick Dowdy and colleagues documented this behavior – technically referred to as acoustic aposematism (“ah-peh-sem-a-tism”), a sound-based antipredator warning – that was previously proven in the laboratory by Wake Forest Professor Dr. Bill Conner and his former graduate student Jesse Barber (now a professor at Idaho State University).

Many birds, reptiles, amphibians, and even plants use visual aposematic signals such as highly contrasting color patterns or specific colors (red is a common theme) to advertise their toxicity. Many bat species prey heavily on moths and although most bats see quite well, they don’t rely solely on vision at night. Instead, they rely more on sound. Therefore it makes sense that the moths, which are primarily nocturnal, could or would develop acoustic signals to deter the bats. “The signals are, in essence, a warning to the bats that the moth is unpalatable and potentially harmful if ingested . . .” said grad student Dowdy.

And the story gets better! Dowdy says that most moths enact evasive dives and spiraling flight when a bat is about to capture them, to which he attributes an energy cost. However, he continues, “We’ve found that this is only sometimes true in tiger moths and different species appear to use these [evasive] behaviors at different rates.” From this he conjectures that certain species may have evolved to rely on their warning sounds instead of the evasive maneuvers that are common to most eared moths. The fact that some of these moths do NOT use evasive maneuvers suggests that their ultrasonic emissions may function as a sonar jamming function that would frustrate sonar-based hunting patterns of otherwise predatory bats.

Copyright© 2016, Pacific Coast Conservation Alliance/Central Coast Bat Survey

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