Behavioural responses of bats to light intensity variation.

Artificial light is a major threat for ecological communities, especially for nocturnal species like bats. Our knowledge on how bats alter their behaviour in response to lit environment is however limited. In order to establish effective mitigation measures, for instance by keeping illumination intensity below the disturbance threshold, it is essential to know how the response of bats to light depends on light intensity. Previous studies have shown that changes in activity vary with light colour, and that red light has the least effect on bat activity. We expect therefore that the intensity thresholds at which species avoid the lit parts of their habitat or stop using commuting routes also vary with the spectral composition of light. This project aims to assess a dose-response relation of bat activity with light intensity for different spectra, and to use this knowledge to prevent habitat loss and fragmentation. In the context of habitat loss, we will estimate bat activity and behavioural shifts at the vicinity of streetlights using microphone arrays to precisely assess flight patterns. We will carry out this experiment at experimentally illuminated transects set up for a long-term study of the impact of light at night. In addition, experimental illumination of landscape corridors (linear water bodies and treelines) combined with acoustic tracking methods will allow us to measure consequences of light on landscape connectivity.