Effects of acoustic environment on male calling activity and timing in Neotropical forest katydids

摘要

Many characteristics of signals can convey information, but the exact timing of the signal often matters as well. The timing of signals is shaped by selective pressures including mate preferences, predation, and competition. In many insect communities, male calling to attract females is persistent and pervasive, and signal timing interactions among individuals are relatively common. In Neotropical forests, many katydid species are represented in the acoustic environment, but calls are usually short ( 40 ms) and infrequent ( 10 s of sound per individual per night), characteristics that have likely evolved in response to intense predation by insectivorous bats. We test two alternative hypotheses about signal timing in environments where signaling is rare and costly, either that timing is absent due to the unpredictable nature of the signals or that the rarity of signals places a premium on signal timing and attention to the acoustic environment. We tested these hypotheses by broadcasting conspecific calls, heterospecific calls, and silence to eight species of katydids and measuring calling activity and call timing in each playback treatment. All species changed the amount or timing of calling (or both) as a result of the playbacks, but species responded differently to playbacks, with some calling more or less during specific treatments and some showing differences in the timing of calls relative to playbacks. Although short latency signal timing was not observed, this study shows that Neotropical forest katydids are responsive to their acoustic environment despite an exceptionally low rate of signaling.