An Investigation into Acoustic Analysis Methods for Endangered Species Monitoring: A Case of Monitoring the Critically Endangered White-Bellied Heron in Bhutan

Passive acoustic recording has great potential for monitoring soniferous endangered and cryptic species. However, this approach requires analysis of long duration environmental acoustic recordings that span months or years. There is a variety of approaches to analysing acoustic data. However, it is unclear which approaches are best suited for monitoring of endangered species in the wild. Specifically, this study is undertaking acoustic monitoring of the critically endangered White-bellied Heron (Ardea insignis) in Bhutan. Four different acoustic analysis methods are investigated in terms of their detection accuracy, involvement of human experts, and overall utility to ecologists for target species monitoring work. Our experimental results show that human pattern detection using a visualization technique has detection performance on par with a cluster-based recogniser, while a machine learning classifier implemented using the same acoustic features suffers from very low precision. Further, specific cases of false positives and false negatives by the different methods are investigated and discussed in terms of their overall utility for ecological monitoring. Based on our experimental results, we demonstrate how an integrated semi-automated approach of human visual pattern analysis with a recogniser is a robust system for acoustic monitoring of target species.