Action: Restrict timing of lighting
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- One study evaluated the effects of restricting the timing of lighting on bat populations. The study was in France.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (1 STUDY)
- Abundance (1 study): One replicated, paired sites study in France found that turning off streetlights for part of the night resulted in mixed results for activity (relative abundance), depending on bat species, when compared with leaving streetlights switched on all night.
USAGE (0 STUDIES)
Dimming or switching off artificial lighting when not in use or at certain times of night (e.g. when bats are most active) may reduce the impact on bats.
Supporting evidence from individual studies
A replicated, paired sites study prior to 2015 at 36 paired rural sites in France (Azam et al 2015) found that turning off streetlights for part of the night resulted in higher activity for two bat species, lower activity for one bat species and similar activity for five bat species when compared with leaving streetlights switched on all night. The average number of bat passes/night was higher with part-night lighting than full-night lighting for Plecotus spp. (part-night lighting: 2.3; full-night lighting: 0.6) and common noctules Nyctalus noctula (data not reported), but lower with part than full-night lighting for common pipistrelles Pipistrellus pipistrellus (part-night lighting: 515; full-night lighting: 1,130). Activity was similar under both light treatments for Kuhl’s pipistrelles Pipistrellus kuhlii, Nathusius’ pipistrelles Pipistrellus nathusii, Leisler’s bats Nyctalus leisleri, serotine bats Eptesicus serotinus and Myotis spp. (see the original reference for detailed results) Each of 36 pairs of sites had one site with streetlighting (high pressure sodium lights, 10–99 lux) and one unlit control site within similar habitats. Streetlights were either turned off for part of the night (between midnight and 05:00 h, 24 sites) or were left on for the full night (12 sites). Each of 36 pairs was sampled simultaneously using bat detectors for one full night between May and August (year not reported).