Quantifying the effect of forest edge on tropical fauna using explainable ecoacoustics metricsa)

Tropical forests are biodiversity reservoirs but are increasingly fragmented by human activity, creating forest edges that alter microclimates and ecological dynamics. Understanding of edge effects is largely based on vegetation studies but still lacks faunal characterization. Here, passive acoustic monitoring was conducted in New Caledonian forests to monitor faunal communities and to examine whether and how the distance from the forest edge structures the soundscape. Recordings were collected at 30 sites located 10 to 300 meters from the edge, and 59 ecoacoustic indices were calculated. Representational similarity analysis with explainable feature-perturbation methods was used to assess relationships between acoustic patterns and edge distance. A low but significant relationship between distance to the edge and acoustic structure was observed at night between 22:00 and 04:00. Six key indices were identified as most influential. Based on these indices, nighttime soundscapes clustered into two groups: near-edge sites (from 10 to 40 m) and interior sites (from 100 to 300 m) were identified. This threshold aligns with previously observed vegetation edge effects fading around 100 meters. Overall, the findings indicate that forest soundscapes can reflect edge effects on faunal activity and highlight the value of explainable, data-driven approaches in ecoacoustic research and biodiversity conservation.