How Do Moth Clicks Decrease the Capture Success of Horseshoe Bats?

Abstract

Moths are among the most diverse and abundant animals. They have evolved a suite of acoustic defenses, such as producing ultrasound to guard against predation by low-duty-cycle bats. Recently, we found that the ultrasonic clicks of several moth species can also help decrease the capture success of high-duty-cycle bats. We tested whether moth clicks could advertise moth toxicity and/or jam the echolocation calls of high-duty-cycle bats. We examined the acoustic response of a hawkmoth (Cechenena minor) and a tiger moth (Creatonotos transiens) to free-flying horseshoe bats, Rhinolophus osgoodi. C. minor and C. transiens produced anti-bat ultrasonic clicks with an average duty cycle of 22.3% and 4.9%, respectively. The clicks of C. minor overlapped spectrally with the echolocation calls of R. osgoodi. C. minor occasionally emitted clicks immediately after the end of bat feeding buzzes. The clicks of C. transiens did not overlap spectrally with the echolocation calls of R. osgoodi. More than half the click sequences of C. transiens were produced before the emergence of bat feeding buzzes and did not overlap temporally with the feeding buzzes. Moreover, we found that C. minor was palatable and C. transiens was unpalatable to R. osgoodi. These results suggest that C. minor might be capable of jamming R. osgoodi and might also use ultrasonic clicks as warning signals. The clicks of C. transiens probably function to advertise moth toxicity. This study highlights the diversity of moth anti-bat sounds and illustrates the potential mechanisms of moth acoustic defense against high-duty-cycle bats.