Suffering in receivers: Negative effects of noise persist regardless of experience in female anurans

Abstract

Anthropogenic noise is widespread, and growing evidence suggests that it can negatively affect animals through many different mechanisms including masking of cues and signals, distraction, and aversion to noise. Acoustic masking has received the most attention from researchers and recent evidence suggests that masking effects can be mitigated by alteration of signal frequencies or amplitudes by signalers. Additionally, alteration can be a learned response via prior experience with noise exposure. However, it remains unclear whether distraction or aversive effects due to noise can be mitigated by prior experience with noise, especially among signal receivers. Here, we addressed this gap by separating mechanisms of noise disturbances on female phonotaxis towards male advertisement calls in anurans. To do this, we experimentally examined phonotaxis of gravid females that differ in their prior experience with noise under three acoustic manipulations: spectrally overlapping and non-overlapping noise that either mask or do not mask male advertisement calls respectively, plus a silent control. We confirm two experience-dependent responses of noisy-site individuals relative to quiet-site individuals: faster initiation of phonotaxis under non-overlapping noise and a stronger aversive response against overlapping noise. However, we showed that, for both noisy- versus quiet-site individuals, both overlapping and non-overlapping noise treatments resulted in delayed initiation and disorientation of phonotaxis relative to silent control treatments. Our study provides the first evidence to demonstrate that, although prior experience appears to mitigate the negative effects of distraction or aversion to noise, prior experience falls short of fully compensating for disrupted orientation through phonotaxis. Additionally, although most studies have emphasized masking of biologically relevant cues and signals as the most prominent mechanism by which noise negatively affects wild organisms, we show that non-overlapping noise, which cannot cause signal and cue masking, can have negative consequences via distraction or aversive responses. This finding suggests that noise impacts could extend well beyond contexts involving acoustic cue detection and discrimination and deserves increased attention by researchers. A plain language summary is available for this article.