Monitoring animal diversity using acoustic indices: Implementation in a temperate woodland

Biodiversity assessment is one of the major challenges for ecology and conservation. With current increase of biodiversity loss during the last decades, there is an urgent need to quickly estimate biodiversity levels. This study aims at testing the validity of new biodiversity indices based on an acoustic analysis of choruses produced by animal communities. The new Acoustic Richness index (AR) and the former dissimilarity index (D) aim at assessing a and 13 diversity respectively. Both indices were tested in three woodland habitats: a mature forest, a young forest and a forest-cropland ecotone within the Parc Naturel Regional of Haute-Vallee de Chevreuse (France). Three recorders running for 74 days generated 5328 files of 150s for a total of 222 h of recording. All files were treated with frequency and amplitude filters to try to remove anthropogenic and environmental background noise. The AR index was in agreement with traditional aural identification of bird species. The AR index revealed an expected gradient of diversity with higher diversity values in the young forest that potentially provides a higher number of microhabitats. The D index also indicated expected differences in the acoustic environment across sites with distinct habitat structure. Both indices reveal significant peak during dawn chorus. These results suggest that diversity could be estimated through acoustics at both alpha and beta scales. Our analyses reveal that, even if background noise needs to be considered with great care, the use of acoustic indices has the potential to facilitate animal diversity assessments over seasons or years and landscape scales. (C) 2011 Elsevier Ltd. All rights reserved.