Background noise constrains communication: acoustic masking of courtship song in the fruit fly Drosophila montana

Drosophila montana males produce a courtship song that is a prerequisite for mating to occur and which females use to select mates. Here we show that D. montana female responses to courtship song decreased in the presence of high levels of noise within the same frequency band as the courtship song, but not in equivalent noise levels in an adjacent higher frequency band. This suggests that high noise levels overlapping the frequency band of the song impair signal detection, but that a mechanism for frequency filtering exists that reduces the influence of noise in adjacent frequency bands. Although the acoustic environment of this species in the wild is not known, some potential sources of noise are discussed. Nevertheless, our findings show that background noise (biotic or abiotic) within the same frequency band as the courtship song of D. montana can mask it, suggesting that environmental noise might affect mate choice and thereby may influence the evolution of this courtship signalling system.