Passive Acoustic Monitoring (PAM) recently extended to a very wide range of animals, but no available open software has been sufficiently generic to automatically treat several taxonomic groups. Here we present Tadarida, a software toolbox allowing for the detection and labelling of recorded sound events, and to classify any new acoustic data into known classes. It is made up of three modules handling Detection, Labelling and Classification and running on either Linux or Windows. This development resulted in the first open software (1) allowing generic sound event detection (multi-taxa), (2) providing graphical sound labelling at a single-instance level and (3) covering the whole process from sound detection to classification. This generic and modular design opens numerous reuse opportunities among (bio)acoustics researchers, especially for those managing and/or developing PAM schemes. The whole toolbox is openly developed in C++ (Detection and Labelling) and R (Classification) and stored at https://github.com/YvesBas

The role of hedgerows in maintaining biodiversity in areas of intensive agriculture is well known, particularly for bats. However, few studies have addressed the importance of the intrinsic characteristics of hedgerows for bats and disentangled the relative effects of local and landscape characteristics of hedgerows on bat activity. In an acoustic survey, we assessed bat activity by recording bat calls using detectors and manually verified all calls using spectrogram analysis. The parameters used to determine local hedgerow structures were the length of the line of trees, of shrub hedgerows, of wooded hedgerows without shrubs and of hedgerows including the three strata (tree, shrub and herb) at a local scale. We assessed the influence of hedgerow structure and on bat activity with an approach considering both species and community, comparing two different scales, the local and the landscape. We highlighted the importance of hedgerow characteristics for bats on both the local and landscape scales even though responses differ between species and spatial scales. We found that the presence of trees in hedgerows exerts a generally positive influence on bat activity and that hedgerows with the three strata had lower bat activity than hedgerows with trees. In our study, some bats seemed to prefer agricultural landscapes dominated by wooded hedgerows and, on the local scale, hedgerows that include trees with little diversified among strata, except for gleaning species. Our study shows that in terms of hedgerow management, conservation efforts must be designed and undertaken on both the local and landscape scales.

Few reports have been published on detection distances of bat calls because the evaluation of detection distance is complicated. Several of the approaches used to measure detection distances are based on the researcher’s experience and judgment. More recently, multiple microphones have been used to model flight path. In this study, the validity of a low-cost and simple detectability metric was tested. We hypothesize that the duration of an echolocating-bat-pass within the area of an ultrasonic bat detector is correlated with the distance of detection. Two independent datasets from a large-scale acoustic bat survey—a total of 25,786 bat-passes from 20 taxa (18 species and two genera)—were measured. We found a strong relationship between these measures of bat-pass duration and published detection distances. The advantages of bat-pass duration measures are that, for each study, experimenters easily produce their own proxy for the distance of detection. This indirect measure of the distance of detection could be mobilized to monitor the loss in microphone sensitivity used to monitor long-term population trends. Finally, the possibility of producing an index for distance of detection provides a weight for each bat species’ activity when they are aggregated to produce a bat community metric, such as the widely used “total activity”.

Sound sequences used to validate the classifier of bat sonotypes (see reference).