Effect of traffic noise on Scinax nasicus advertisement call (Amphibia, Anura)

Abstract

Increased anthropogenic-made sounds such as traffic noises contribute to acoustic pollution, which produces deleterious effect on songvertebrates. We compared the advertisement call of Scinax nasicus (Cope, 1862) males in natural (as a reference or control, Site A) and Sites affected by traffic noises (Site B). Call structure was recorded and it was amplified in sonograms (software Raven Pro 1.5). Seven variables were measured on its advertisement call: duration (s), number of notes, number of pulses per note, maximum and minimum frequency (kHz), dominant frequency (kHz) and amplitude (dB). In addition, at each Site the background noise (the fundamental frequency, F0 and amplitude, dB) was measured. The amplitude of background noise reached higher values (68.02 dB) in Site B, while in Site A was lower (34.81 dB). Thus, the F0 in Site A was 6.28 kHz and in Site B it was 4.15 kHz. Frog call in noisy environment (Site B) were characterized by lesser duration (s) and number of pulses per note, higher maximum and dominant frequencies (kHz), lower minimum frequencies, and amplitude (dB) when compared with control environment (Site A). Our study highlights, that S. nasicus males shift their vocal structure in traffic noisy ponds, mainly by vocal “adjust” of their frequencies and amplitude to counteract masking effect. Finally, acoustic monitoring of anurans on noise environments should be considering the spatial, temporal and spectral overlap between noise and species-specific acoustic behaviour.