A Multiscale Approach to Investigate the Biosemiotic Complexity of Two Acoustic Communities in Primary Forests with High Ecosystem Integrity Recorded with 3D Sound Technologies

Abstract

The biosemiotic complexity of acoustic communities in the primary forests of Ulu Temburong (Brunei, Borneo) and Yasuni (Ecuador, Amazon) was investigated with continuous 24-h recordings, using the acoustic signature and multiscale approach of ecoacoustic events and their emergent fractal dimensions. The 3D recordings used for the analysis were collected in undisturbed primary equatorial forests under the scope of the project, Fragments of Extinction, which produces 3D sound portraits with the highest definition possible using current technologies – a perfect dataset on which to perform a multiscale qualitative analysis. The ecoacoustic events (EEs) detected by a combination of the Acoustic Complexity Indices, ACIft, ACIft evenness, and ACItf evenness, and its fractal dimension were developed according to a biosemiotics approach in which the ecofield theory states that EE functions like a species-specific carrier of meaning. EEs, extracted according to 10 levels of temporal resolution, from 1 to 360 s, confirm the hypothesis that these acoustic communities have an internal complexity that responds to a fractal structure (fractal dimension D of Ulu Temburong D = 1.33 versus Yasuni D = 1.31). Yasuni was richer in EEs, with a higher coefficient of variation of hourly fractal dimension (Yasuni: D = 6.16 versus Ulu Temburong: D = 2.66). This methodology opens up promising new perspectives in the acoustic assessment of habitat quality and monitoring landscape modification. It also confirms the great potential of the biosemiotics approach in converting acoustic frequencies into ecoacoustic events through encoding procedures that mimic potential species-specific interpretations of the sonic environment.