Avoid illumination of bat foraging, drinking and swarming sites

Overall effectiveness category Likely to be beneficial
Number of studies: 2
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How is the evidence assessed?

Effectiveness

80%
Certainty

52%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Key bat habitats such as foraging, drinking and swarming sites should be left unlit to avoid disturbance to bats. Dark buffer zones may also be retained around them.

Study locations

Key messages

Two studies evaluated the effects of avoiding the illumination of bat drinking sites on bat populations. Both studies were in Italy and one was also in Israel.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): Two replicated before-and-after studies (one randomized) in Italy found that unlit water troughs had greater activity (relative abundance) of five of six bat species/species groups and six of eight bat species/species groups than troughs illuminated with artificial light. One of the studies also found that unlit desert ponds in Israel had greater activity (relative abundance) of three bat species than illuminated ponds.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, randomized, before-and-after study in 2015 of four cattle troughs within forest in central Italy (Russo et al 2017; same study area as Russo et al 2019) found that unlit troughs had higher drinking activity for five of six bat species/species groups than troughs illuminated with artificial light. More drinking buzzes were recorded for five bat species/species groups when troughs were unlit than when they were illuminated with artificial light: barbastelle bat Barbastella barbastellus (unlit: 584; lit: 306), brown long-eared bat Plecotus auritus (unlit: 78; lit: 0), Myotis spp. (unlit: 599; lit: 134), Kuhl’s pipistrelle Pipistrellus kuhlii (unlit: 116; lit: 64) and Savi’s pipistrelle Hypsugo savii (unlit: 39; lit: 10). For the common pipistrelle Pipistrellus pipistrellus, the difference was not significant when troughs were unlit (240 drinking buzzes) or illuminated (165 drinking buzzes). Each of four cattle troughs consisted of two troughs (6 x 1.5 m) joined together. Troughs were illuminated with a portable LED (light-emitting diode) white light (average 49 lux). Each of four sites was surveyed using bat detectors on two nights with five randomized lit and unlit 10-minute periods/night in July–August 2015.
Study and other actions tested
Referenced paper
Russo D., Cistrone L., Libralato N., Korine C., Jones G. & Ancillotto L. (2017) Adverse effects of artificial illumination on bat drinking activity. Animal Conservation, 20, 492-501.
A replicated, before-and-after study in 2015–2016 at six cattle troughs within forest in Italy and three natural desert ponds in Israel (Russo et al 2019) found that unlit troughs within forests had higher drinking activity for six of eight bat species/species groups than troughs illuminated with artificial light, and unlit desert ponds had higher drinking activity for all of three bat species than illuminated ponds. At forest sites, more drinking buzzes (average/30 min interval) were recorded when troughs were unlit than when they were illuminated for barbastelle bat Barbastella barbastellus (unlit: 250; illuminated: 140), Myotis spp. (unlit: 160; illuminated: 40), Natterer’s bat Myotis nattereri (unlit: 35; illuminated: 8), brown long-eared bat Plecotus auritus (unlit: 50; illuminated: 4), common pipistrelle Pipistrellus pipistrellus (unlit: 88; illuminated: 76) and Leisler’s bat Nyctalus leisleri (unlit: 11; illuminated: 4). The difference was not significant for Kuhl’s pipistrelle Pipistrellus kuhlii (unlit: 28; illuminated: 46) or Savi’s pipistrelle Hypsugo savii (unlit: 18; illuminated: 7). At desert sites, more drinking buzzes were recorded when ponds were unlit than when they were illuminated for desert pipistrelle Hypsugo bodenheimeri (unlit: 1,040; illuminated: 260), trident bat Asellia tridens (unlit: 240; illuminated: 70) and Kuhl’s pipistrelle (unlit: 45–1,270; illuminated: 10–350). Troughs (same study area as Russo et al 2017) and ponds were illuminated with a portable LED (light-emitting diode) white light. At each of nine sites, one bat detector recorded bat activity for four hours on two consecutive nights (one unlit, one lit) in July–August 2015 (forest) and July 2016 (desert).
Study and other actions tested
Referenced paper
Russo D., Ancillotto L., Cistrone L., Libralato N., Domer A., Cohen S. & Korine C. (2019) Effects of artificial illumination on drinking bats: a field test in forest and desert habitats. Animal Conservation, 22, 124-133.

Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2021) Bat Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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This Action forms part of the Action Synopsis:

Bat Conservation

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