Are Green Bridges Used by Bats to Safely Cross the Road?

Roads have a multitude of direct negative effects on wildlife due to collisions and noise and play a prominent role in overall habitat fragmentation. For bats, landscape fragmentation by roads causes disturbance during nocturnal movements and road kill negatively affects local abundance and bat population dynamics. Mitigation measures such as wildlife crossings (green bridges) are among the proposed improvements intended to reduce the fragmentation impact of roads for many taxa, but their efficiency has rarely been tested for bats. In this study, we performed a control-impact analysis to assess the efficiency of two structures on the number of bat crossings by assessing their collision risk using an acoustic flight path reconstruction (AFPR) approach. We obtained data for 458 crossings for six bat taxa that showed how the number of bat crossings is significantly higher on green bridges than control sites for all species (pooled) and for two guilds — one with species with a low flight height and the other with a higher flight height. We also found that bat activity on either side of a green bridge is not a predictor of the true use of the bridge to cross roads. Considering these results, wildlife crossings can be envisaged as a mitigation measure to reduce impacts of road construction on bat movements.