Number of frogs per pond per night per stimulus

In tropical regions, some anuran species “explosively breed”, reproducing in massive and highly diverse aggregations during a brief window of time. These aggregations can serve as acoustic beacons, attracting other anurans towards seasonal ponds. We hypothesize that conspecific and heterospecific calls play a role in navigation towards ponds and synchronization of reproduction among species. We simulated a chorus of two species (Trachycephalus coriaceus and Chiasmocleis shudikarensis) with contrasting call characteristics (low-frequency vs. high-frequency) and reproductive strategies (strict pond breeder vs. opportunistic) near known explosive breeding sites and predicted that choruses of T. coriaceus are more attractive to heterospecifics than of C. shudikarensis because the first provides a more reliable indicator of a suitable breeding pond and a better long-distance signal. We found that both choruses attracted conspecific frogs to the playback outside a natural breeding event. As predicted, heterospecifics were attracted only by low-frequency calls of T. coriaceus that breeds exclusively in large ponds, but not by higher-frequency calls of C. shudikarensis that also breeds in small pools not suitable for other species. Our study presents the first experimental evidence that tropical explosive breeding anurans are attracted to conspecific and heterospecific choruses. The contrasting effect of the playback of the two species on heterospecifics suggests that the attractive effect of a chorus depends on the reproductive strategy of both the sender and the receiver. Given the abundance and diversity of communities in tropical ecosystems, the use of heterospecific acoustic cues may prove widespread and requires further investigation.