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We are interested in the problem of classifying commuting and foraging behaviour of bats at delimited geographical areas, namely sites, throughout France. To predict the majority behaviour on these sites, we use echolocation call data recorded as part of Vigie-Chiro participatory project. As the temporal distribution of calls is a relevant indicator of behaviour, providing an adequate model of this distribution is a matter of great interest. Given the self-exciting dynamics observed in foraging behaviour, we propose to model bat calls by Hawkes processes. Specifically, we consider that the start time of each call emitted on a site is an event of a Hawkes process. Taking advantage of this modelling, we use a suitable procedure that relies on the empirical risk minimization principle to discriminate between the 2 classes. Then, the performance of the procedure is assessed on synthetic data through comprehensive numerical experiments. The overall methodology is evaluated with a goodness-of-fit test. Finally, we present the obtained results on the real data set. The classification results are convincing and show the relevance of our method, which could contribute to a better understanding of behavioural determinants and open up broad perspectives in spatial ecology. [ABSTRACT FROM AUTHOR]

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The development of transportation infrastructure has been identified as one of the main pressures on biodiversity. The effects of transport infrastructure are more documented for terrestrial mammals, birds and amphibians than for bats. To assess the impacts of roads on bat activity, we carried out full-night acoustic recordings of bat calls at 306 sampling points at different distances from a major road at three study sites in France. To assess the relationship between bat activity and the distance to the major road, we performed generalized linear mixed model analyses for thirteen different species or groups and additionally explored the non-linear effect with generalized additive mixed models. Our results showed that low-flying species are more affected than high-flying species. Indeed, we found a significant negative effect of major roads on bat activity for the 'clutter-adapted' species, Eptesicus serotinus , Myotis spp., Pipistrellus pipistrellus and Rhinolophus hipposideros. These results demonstrate that the road-effect zone of major roads extends up to five kilometres. Extrapolating those road-effects zones to the major roads in the European Union, we estimated that 35% of the European Union is potentially negatively impacted. Finally, it seems urgent to consider these road effects with the cumulative effects of other roads by improving habitat connectivity and foraging areas in land use policies. Additionally, to implement drastic conservation practices for species of conservation concern in environmental impact assessment studies, efficient mitigation and offset measures implemented should be sized proportionally to the disturbance caused. • Major roads affect activity in five of the thirteen studied taxa. • Low-flying species are more affected than those that fly in the open. • Road impacts may be due to road kills, traffic disturbance and ruptured connectivity. [ABSTRACT FROM AUTHOR]

Acoustic detectors have become increasingly used by bat workers to investigate bat ecology and assess the impacts of anthropogenic pressures. Within these studies, the metric used, 'bat activity', is based on the number of bat passes, without considering the bat pass duration (i.e. each event of a bat detected within the range of an ultrasonic detector). We expected that bat pass duration may contain information about site quality in terms of foraging potential. Because bats are expected to have a more sinuous trajectory and slower velocity when they exhibit foraging behaviour, as opposed to commuting behaviour, we hypothesize a longer bat pass duration in favourable habitats; during seasons with important energetic demands; or during night peak activity. We used datasets from a large-scale acoustic bat survey (n = 2890 sites), with a total of 24,597 bat pass measures from 6 taxa, and performed GLMM modelling. We detected a significant effect of habitat type on bat pass duration for five taxa. Shorter bat pass durations were detected at the beginning of the night. We detected longer pass durations during the lactation period or just before hibernating, while weather conditions or ageing and wear of the detector rarely influenced bat pass duration. Bat pass duration appears to be a simple and easy measure for position calls on a gradient between commuting vs. foraging behaviour. We suggest that the traditional measure of bat activity may be weighted by bat pass duration by giving more weight to events with potentially stronger links to foraging behaviour. [ABSTRACT FROM AUTHOR]

The use of echolocation allows insectivorous bats to access unique foraging niches by locating obstacles and prey with ultrasounds in complete darkness. To avoid interspecific competition, it is likely that sonar features and wing morphology co-evolved with species vertical distribution, but due to the technical difficulties of studying flight in the vertical dimension, this has never been demonstrated with empirical measurements. The authors equipped 48 wind masts with arrays of two microphones and located the vertical distribution of a community of 19 bat species and two species groups over their annual activity period (>8000 nights). The authors tested the correlation between the proportion of flights at height and the acoustic features of bat calls as well as their wing morphology. The authors found that call peak frequency and bandwidth are good predictors of bat use of the vertical space regardless of their acoustic strategies (i.e., gleaning, hawking, or detecting prey flutter). High wing aspect ratios and high wing loadings were associated with high proportions of time spent at height, confirming hypotheses from the literature. [ABSTRACT FROM AUTHOR]

The pied butterfly bat, Glauconycteris superba, is endemic to the tropical forest zone of Africa, where it was previously known from only five specimens. Here we report the capture of 10 individuals in two localities of the Democratic Republic of the Congo (Mbiye Island and Yoko forest reserve), and we present the first acoustic data of the species recorded using a conventional microphone and a home-made acoustic system for real time 3D localization. Our morphological comparisons show that females are larger and heavier than males, and that the two sexes exhibit the same fur coloration pattern. We found some individual variations concerning the width of the two lateral white stripes on the belly, and the number and extension of white shoulder-spots. The echolocation recordings show evidence for alternation between two call types (A and B), differing in frequency, bandwidth, and duration. The acoustic signals obtained before captures and after releases revealed important variations depending on the trajectories and environmental conditions. Acoustic characteristics, wing measurements, and the unique black and white fur pattern of G. superba suggest that it is a canopy species able to fly at high speeds. Our findings will be useful for future ecological studies to provide new data on the range, population size, trend and threats of G. superba in order to better assess its conservation status. [ABSTRACT FROM AUTHOR]

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". [ABSTRACT FROM AUTHOR]