Anthropogenic noise impact on bat communities

Anthropogenic noise is a globally increasing environmental disturbance with several implications for wildlife. However, our understanding of its effects is still limited. The study aimed to investigate the impact of anthropogenic noise on bat communities. In 2023, a field experiment was conducted involving the emission of controlled white noise at 110 dB (Sound Pressure Level) using the dodecahedral Norsonic AS sound source. Throughout the experiment, the acoustic environment in the study area was characterised using phonometers. The experimental design followed the principle of treatment versus control with a Before/After-Control/Impact (BACI) approach. Study areas chosen for noise exposure and control were selected based on habitat type and environmental characteristics. For the first replicate, two sampling points were selected at distances of 100 and 200 m from the sound source. For the second replicate, four sampling points were investigated at 25, 50, 100 and 200 m. Bat communities were surveyed using automatic bat detectors (Wildlife Acoustics). Acoustic data were analysed using Sonochiro® software to identify recordings containing bat calls. This initial stage of the research focused only on the total number of bat calls recorded. During the first replicate, the sampling points were too distant to detect any noise effect. However, analysis of the second replicate revealed a negative correlation between SPL and the number of bats calls. Bat calls decreased with increasing SPL, and the effect was more pronounced at sampling points closer to the sound source (25 and 50 m). Furthermore, when comparing silent nights to nights with disturbance in the treatment area, a significant difference in the number of calls was observed at the points closest to the sound source (25 and 50 m). This comprehensive approach will contribute to a deeper understanding of the ecological consequences of anthropogenic noise on bat populations and inform effective conservation strategies.