Conservation Evidence strives to be as useful to conservationists as possible. Please take our survey to help the team improve our resource.

Providing evidence to improve practice

Action: Use red lighting rather than other lighting colours Bat Conservation

Key messages

Read our guidance on Key messages before continuing

  • Three studies evaluated the effects of red lighting on bat populations. One study was in the UK, and two studies were in the Netherlands.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

  • Abundance (2 studies): One replicated, controlled, site comparison study in the Netherlands found that red lighting resulted in higher activity (relative abundance) for one of three bat species groups than white or green lighting. One site comparison study in the Netherlands found that culverts illuminated with red light had similar activity of commuting Daubenton’s bats as culverts illuminated with white or green light.

BEHAVIOUR (1 STUDY)        

  • Behaviour (1 study): One replicated, controlled study in the UK found that more soprano pipistrelles emerged from a roost when lit with red light than when lit with white light, but no difference was found between red and blue lights.

Supporting evidence from individual studies

1 

A replicated, controlled study in 2000 at two bat roosts within buildings in Aberdeenshire, UK (Downs et al. 2003) found that when roosts were illuminated with red light more soprano pipistrelles Pipistrellus pygmaeus emerged than when roosts were illuminated with white light, but no difference was found between red and blue lights. At both roosts, more bats emerged when the roost entrance was illuminated with red light (13 and 72 bats) than when it was illuminated with white light (2 and 24 bats). No difference was found between red and blue light (6 and 62 bats emerging) at either roost. A hand-held halogen light with coloured filters was placed within 3–5 m of each of the two roosts. Over 20 nights in July–August 2000, nights with roosts unlit and nights with lighting were alternated. On nights with lighting, white, blue and red lights were rotated in a random order and changed every 30 seconds. On each of 20 nights, the number of bats emerging per 30 second interval was counted at dusk.

2 

A replicated, controlled, site comparison study in 2012–2016 at eight forest sites in the Netherlands (Spoelstra et al. 2017) found that red lighting had higher activity for one of three bat species groups than white or green lighting, and similar activity was recorded for all three species groups in red lighting and darkness. For Myotis and Plecotus spp. more bat passes were recorded in red light (66) and darkness (67) than in white (31) and green light (22). For Pipistrellus spp. fewer bat passes were recorded in red light (5,940) and darkness (3,655) than in white (17,157) and green light (9,695). None of the light treatments had a significant effect on the number of bat passes recorded for Nyctalus or Eptesicus spp. (red light: 495; white light: 719; green light: 950; dark: 521). At each of eight sites, one 100 m transect was set up for each of four treatments (red light, white light, green light or left dark). Five 4 m high light posts were installed along each transect. Lights (8 lux) were turned on from sunset to sunrise. Bat detectors recorded bat activity for 5–15 nights/transect in June–July and August–September in each year between 2012 and 2016.

3 

A site comparison study in 2015 of two road culverts near Elburg, Netherlands (Spoelstra et al. 2018) found that culverts illuminated with red light had similar activity of commuting Daubenton’s bats Myotis daubentonii as culverts illuminated with green or white light. The average number of Daubenton’s bat passes did not differ significantly between culverts illuminated with red (43 bat passes/night), green (37 bat passes/night) or white light (39 bat passes/night). Activity was similar when culverts were left unlit (34 bat passes/night). Two light-emitting diode (LED) lamps of three colours (red, green, white) were installed on the ceiling of each of two identical, parallel road culverts (31 m long, 1.6 m diameter) carrying a stream. Different light treatments (unlit; red, green, or white light at 5 lux intensity) were applied simultaneously in each of the two culverts with treatments changed each night over a total of 47 nights in July–August 2015. Two bat detectors fitted alongside the lamps in each of the two culverts recorded bat activity.

Referenced papers

Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2019) Bat Conservation. Pages 67-140 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.