The response behaviour of bats to motion-controlled LED lighting of bicycle trails

Increasing illumination of bicycle trails at night can have an impact on nocturnal animals such as bats. We asked whether motion-triggered LED lights may reduce the negative impact on bats. On a newly LED-lit bicycle trail, we measured the flight and hunting activity of bats in response to LED lighting that was switched on for 40 s when cyclists passed by. In addition, we investigated flight movements of bats close to lampposts with thermal imaging. The study area was located in the city of Münster, Germany, along a 1.5 km test stretch of a newly LED-lit bicycle trail. We selected 5 lampposts with a distance of 210 m to 300 m to each other along the trail that bordered different habitat types (open field, forest, forest/residential area, residential area, park). We equipped each of the 5 lampposts with an echolocation call detector and a light and temperature sensor. Acoustic bat activity was recorded automatically from about 15 minutes before sunset and after sunrise in parallel to light and temperature measurements at all sites simultaneously. Sites were sampled across three nights each during the reproduction season (June/July) and the migration season (August/September) 2022. To track individual bat movements, we used a thermal imaging camera-tracking system with two thermal imaging cameras. From the video recordings, we identified x-, y- and z-coordinates (3D-position) of individual bats. Nine 3D-tracks were recorded and the 18th of October 2022, while three tracks were recorded on the 19th of October 2022. All 3D-tracks were recorded while LED lights were off.