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Artificial light at night (ALAN) affects biodiversity conservation through its impacts on spatio-temporal distribution patterns of species, in particular bat species. The development of this threat underlines the urgency to adopt lighting practices (characteristics) that have the least impact on species, in particular the most vulnerable species still present in semi-natural areas. It is therefore crucial to better assess the relative effects of the different light parameters for a wide variety of species. Our study investigates the relative effects of streetlights characteristics, i.e. height, lamps type (HPS, LED), illuminance, and the distance to a streetlight on the activity of a variety of species (15) according to their flight traits. We compared bat species activity in lit and dark conditions along streets and in hedges at less than 200 m away from streetlights of various characteristics, in a Mediterranean protected area.Lighting had contrasting effects on the activity of clutter and aerial bat species, with a strong negative effect on clutter species (90% reduction of bat activity), half of which are strictly protected. Illuminance particularly affected their activity.Among the possible management options to reduce the effect of light pollution at night (reduction of light intrusion by modifying the height of street lamps, lighting intensity, spectral composition), the removal of light sources, or at least the reduction of illuminance, seems to be the most effective option. Due to its strong impact on highly protected species, we urge the need to manage lighting, in particular in protected areas. Capsule: Artificial light at night had a negative effect on clutter bats activity (90% reduction of bat activity) and among streetlight characteristics illuminance was the most relevant. Data accessibility: Data used for statistical analysis are include in Appendix C. Acoustic row data was delivered to the citizen science program “VigieChiro” (https://vigiechiro.herokuapp.com/).

Ce présent rapport expose les résultats du projet Chirolum ayant pour objectif d'identifier des pistes de réduction des impacts écologiques de l'éclairage artificiel le long des infrastructures de transport. En prenant l'exemple de sites d'études le long de lisières forestières aux Pays-Bas et le long du Canal du Midi à Toulouse, les résultats montrent que la lumière perturbe fortement l'usage de ces continuités écologiques et infrastructures de transport par les chauves-souris, engendrant des modifications dans le comportement de vol et potentiellement des coûts énergétiques supplémentaires, ainsi qu'une diminution de la connectivité fonctionnelle. Le projet met en évidence que le meilleur levier d'action reste d'éteindre autant que possible les sources de lumière, en montrant notamment que des impacts forts persistent même en changeant la couleur d'éclairage vers du rouge contenant peu de lumière bleue et d'ultraviolets et en diminuant l'intensité. Cependant le projet révèle aussi que les perturbations ne semblent pas s'étaler à plus de quelques dizaines de mètres des sources lumineuses, et que la direction de l'éclairage constitue un paramètre clé sur lequel il est possible d'agir afin de réduire les impacts, en évitant notamment de diriger les éclairages vers les corridors écologiques. Enfin le projet révèle aussi que les perturbations comportementales et fonctionnelles observées au sein de la ville de Toulouse sont le fruit d'un manque de gestion du parc d'éclairage vers des schémas d'extinction ou de réduction, exacerbé par un manque de communication entre services institutionnels susceptibles d'intervenir dans les politiques de prise en compte des enjeux biodiversité en lien avec l'éclairage artificiel.

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„.

International audience; The increased use of pesticides and tillage intensification is known to negatively affect biodiversity. Changes in these agricultural practices such as herbicide and tillage reduction have variable effects among taxa, especially at the top of the trophic network including insectivorous bats. Very few studies compared the effects of agricultural practices on such taxa, and overall, only as a comparison of conventional versus organic farming without accurately accounting for underlying practices, especially in conventional where many alternatives exist. Divergent results founded in these previous studies could be driven by this lack of clarification about some unconsidered practices inside both conventional and organic systems. We simultaneously compared, over whole nights, bat activity on contiguous wheat fields of one organic and three conventional farming systems located in an intensive agricultural landscape. The studied organic fields (OT) used tillage (i.e., inversion of soil) without chemical inputs. In studied conventional fields, differences consisted of the following: tillage using few herbicides (T), conservation tillage (i.e., no inversion of soil) using few herbicides (CT), and conservation tillage using more herbicide (CTH), to control weeds. Using 64 recording sites (OT = 12; T = 21; CT = 13; CTH = 18), we sampled several sites per system placed inside the fields each night. We showed that bat activity was always higher in OT than in T systems for two (Pipistrellus kuhlii and Pipistrellus pipistrellus) of three species and for one (Pipistrellus spp.) of two genera, as well as greater species richness. The same results were found for the CT versus T system comparison. CTH system showed higher activity than T for only one genus (Pipistrellus spp.). We did not detect any differences between OT and CT systems, and CT showed higher activity than CTH system for only one species (Pipistrellus kuhlii). Activity in OT of Pipistrellus spp. was overall 3.6 and 9.3 times higher than CTH and T systems, respectively, and 6.9 times higher in CT than T systems. Our results highlight an important benefit of organic farming and contrasted effects in conventional farming. That there were no differences detected between the organic and one conventional system is a major result. This demonstrates that even if organic farming is presently difficult to implement and requires a change of economic context for farmers, considerable and easy improvements in conventional farming are attainable, while maintaining yields and approaching the ecological benefits of organic methods.

International audience; Acoustic detectors have become increasingly used by bat workers to investigate bat ecology and assess 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 volume of an ultrasonic detector); we expected that bat pass duration may contain information about site quality in terms of potentialities for foraging. 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 greater bat pass duration in favourable habitats; during seasons with important energetic demands; or during night pic activity. We datasets from a large-scale acoustic bat survey (n=2890 sites), allowing a total of 24597 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. Smaller bat pass durations were detected in 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 the events with potentially greater links to foraging behaviour.

Aim We measured the changes in an island avifauna over more than 100 years (1898–2006), using community indices accounting for difference in expected species sensitivity to land-use and climate changes. Location Ouessant Island, France, Great Britain. Methods We assessed the temporal trend of the relative proportion of generalist species breeding on Ouessant island and whether high-temperature tolerant species have replaced less tolerant species over this time period. We further tested the relationship between the observed change in the avifauna composition, and long-term population species’ trends measured independently in potential source regions of colonist species (France and Great Britain). Results During the whole study period, Ouessant island has experienced a strong increase in species richness (+41%), but a severe decline in specialist species. In contrast, we found no change in species composition in terms of their temperature-tolerance. The observed trend was highly correlated with species trends measured in the Great Britain. Main conclusions Our results revealed an ongoing biotic homogenization process towards more generalist species, coupled with a strong local increase in species richness. The observed trend was most likely driven by a strong habitat change in the island occurring during the period considered, favouring the colonization of generalist species. Our results show that an increase in species richness can be misinterpreted as a sign of conservation improvement and that assessing change in community composition using species-specific ecological traits provides more accurate insights for conservation planning purposes.