Sensory-motor tuning allows generic features of conspecific acoustic scenes to guide rapid, adaptive, call-timing responses in Túngara frogs

Male frogs court females from within crowded choruses, selecting for mechanisms allowing them to call at favorable times relative to the calls of rivals and background chorus noise. To accomplish this, males must continuously evaluate the fluctuating acoustic scene generated by their competitors for opportune times to call. Túngara frogs produce highly frequency- and amplitude-modulated calls from within dense choruses. We used similarly frequency- and amplitude-modulated playback tones to investigate the sensory basis of their call-timing decisions. Results revealed that different frequencies present throughout this species’ call differed in their degree of call inhibition, and that lower-amplitude tones were less inhibitory. Call-timing decisions were then driven by fluctuations in inhibition arising from underlying frequency- and amplitude-modulation patterns, with tone transitions that produced steeper decreases in inhibition having higher probabilities of triggering calls. Interactions between the varied behavioral sensitivities to different conspecific call frequencies revealed here, and the stereotyped amplitude- and frequency-modulation patterns present in this species’ calls, can explain previously surprising patterns observed in túngara frog choruses. This highlights the importance of understanding the specific sensory drivers underpinning conspecific signaling interactions, and reveals how sensory systems can mediate the interplay between signal perception and production to facilitate adaptive communication strategies.

Methods
In this study, we preformed playback experiments to calling male túngara frogs to see how amplitude and frequency modulation in tonal playback stimuli influenced their call-timing decisions. From the results, we gained some clues regarding the functioning of their call timing mechanisms.