Biophony in a noisy tropical urban forest fragment

Abstract

Anthropogenic noise, which is part of an urban soundscape, can negatively affect the behaviour of wild animals. Here we investigated how biophony (animal sounds) was affected by noise in an urban Brazilian forest fragment. Our hypothesis was that noise and biophony would differ between the border and the centre of the forest fragment (i.e., lower biophony predicted in noisy areas). Two passive acoustic monitoring devices were used to record soundscapes one week per month, 24 hour per day, from May to July 2012. The Acoustic Complexity Index (ACI) was used to quantify biophony and the Power Spectral Density (PSD) to quantify urban noise. PSD and ACI were higher on the border than in the centre of the fragment. PSD was lower in July, while the ACI did not significantly vary between months. Noise levels were also higher on the border. Conversely, potential species richness was higher in the centre of the forest fragment. Higher biophony at noisy sites can be interpreted as behavioural responses of species for communicating in noisy areas. Alternatively, they could be the result of species segregation by degree of vocal plasticity or due to differences in composition of communities.

Caracterización acústica de fincas bajo pago por servicios ambientales en la Reserva Forestal Golfo Dulce, Costa Rica

“…Los índices SPLm y MAE fueron los más importante en la clasificación de conglomerados de acuerdo con los índices acústicos. Los valores más bajos de SPLm y MAE se asocian principalmente con sitios conservados, siendo estos los más silenciosos (Gonçalves et al, 2021). Estas diferencias en la energía acústica pueden deberse a la estructura y composición de la vegetación y su relación con la propagación del sonido (Slabbekoorn, 2004), o bien a la influencia de sonidos antrópicos (Fairbrass et al, 2017;Mitchell et al, 2020).…”