Timescales of call variability in a South American treefrog.

Communication systems shape behavioral interactions that are crucial for recognition, territoriality, and reproduction across animals. In many anuran species, acoustic communication drives reproductive and defensive behaviors as males produce advertisement calls to establish territories and attract females. Understanding the temporal dynamics in vocalizations and their variation between and within males can provide crucial insight into the mechanisms that generate call patterning and communication. Here, we examine such dynamics in the call patterning of male Boana pulchella, a South American treefrog species that produces temporally-variant call series over time. Using rhythm analysis, we quantify the rhythmic structure of these vocalizations and characterize the variability in their temporal patterning between males. We find that rhythmic isochrony is timescale-dependent - call series are produced isochronously while the patterning of calls and notes within these series is non-isochronous yet periodic. The isochronous rhythm is maintained through an inverse relationship between series duration and the silence interval that follows it, such that longer series are followed by shorter silence intervals. Temporal features of calls and notes as well as their variation vary depending on within-series patterning dynamics and across timescales. Taken together, these results suggest that B. pulchella vocal timing is generated by hierarchically organized oscillators that produce isochronous vocalizations over a calling bout through flexible modulation at finer timescales.