Past research had revealed that many night-flying moths have evolved the ability to hear bat sonar. A number were even seen responding with clicks of ultrasound.
Other studies revealed that moth ultrasound could startle bats off. Research also showed the outbursts could warn bats that such moths had a nasty taste, just as flashy colors on some animals can serve to ward off potential predators. Still, there was the enticing possibility that some moths used ultrasound to actually foil bat sonar.
To look for a case of sonar jamming, investigators employed ultrasonic recordings and high-speed infrared video to analyze how big brown bats (Eptesicus fuscus) interacted with one particular species of ultrasound-emitting tiger moth (Bertholdia trigona) over the course of nine nights in enclosed rooms.
If the moth sounds were just meant to startle bats, bats would eventually get used to the outbursts and go on to catch the moths. If the insect clicks were just meant to warn bats they were unpalatable, the bats would have stopped attacking the moths after trying one first.
However, the researchers saw that bats neither increased nor decreased their odds of catching these moths, and instead their ability to catch the moths remained consistently poor over time. This suggested the ultrasound bursts were not meant to startle the bats nor warn of bad taste. As such, the insects might have evolved a genuine sonar-jamming defense mechanism to save them from bats.