Prey exploits the auditory illusions of eavesdropping predators

Mating signals have evolved to attract target receivers, even to the point of exploiting receivers through perceptual manipulation. Signals, however, can also expose signalers to non-target receivers, including predators and parasites, and thus have also evolved to decrease enemy attraction. Here we show that male treefrogs (Smilisca sila) reduce their attractiveness to eavesdropping enemies (bats and midges) by overlapping their calls at near-perfect synchrony with the calls of neighboring conspecifics. By producing calls that closely follow those of other males, synchronizing S. sila take advantage of an auditory illusion where enemies are more attracted to the leading call. Female S. sila, however, are not as susceptible to this illusion. Thus, synchronization among signaling males can result in acoustic crypsis from predators without affecting female attraction. Given the widespread use of conspicuous mating signals and eavesdropping enemies, perceptual exploitation of eavesdroppers is likely a common driver of signal evolution.

Methods
Data from laboratory and field acoustic playback experiments assessing the leader-follower call preferences in the target receiver (female frogs: "pugnosed_l-f_data.csv" and "tungara_l-f_data.csv") and non-target eavesdroppers (bats: "bat_l-f_data", and midges: "midge_l-f_data").