Collected Evidence: Collected Evidence: Leave bat roosts and roost entrances unlit Five studies evaluated the effects of leaving bat roosts and roost entrances unlit on bat populations. Two studies were in the UK, and one study was in each of Canada, Hungary and Sweden. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Abundance (1 study): One replicated, controlled study in Canada found that numbers of big brown bats and little brown bats roosting in buildings increased when roosts were left unlit and decreased when roosts were illuminated with artificial lights. Condition (1 study): One replicated, controlled study in Hungary found that juvenile bats had a higher body mass and greater forearm length at unlit roosts than at roosts with artificial lighting. BEHAVIOUR (4 STUDIES)      Use (1 study): One replicated, before-and-after study in Sweden found that all of 13 unlit churches continued to be used by brown long-eared bat colonies over 25 years, but bat colonies abandoned their roosts at 14 of 23 churches that were either partly or fully lit with floodlights. Behaviour change (3 studies): Three controlled studies (including two replicated studies) in the UK and Hungary found that more bats emerged, and bats emerged earlier and foraged for shorter periods, when roosts were left unlit than when they had artificial lighting. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1017https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1017Fri, 20 Dec 2013 17:54:28 +0000Collected Evidence: Collected Evidence: Use low intensity lighting Three studies evaluated the effects of using low intensity lighting on bat populations. The three studies were in the UK. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Abundance (2 studies): One replicated, randomized, controlled study in the UK found that activity (relative abundance) of lesser horseshoe bats, but not myotis bats, was higher along hedges with medium or low intensity lighting than hedges with high intensity lighting. One replicated, randomized, controlled study in the UK found that activity of myotis bats, but not common pipistrelles, was higher along treelined roads with street lights dimmed to an intensity of 25% than roads with streetlights dimmed to 50% or left undimmed. BEHAVIOUR (1 STUDY)         Behaviour change (1 study): One replicated, controlled study in the UK found that more soprano pipistrelles emerged from two roosts when the intensity of red lights was reduced by placing filters over them. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1018https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1018Fri, 20 Dec 2013 17:58:34 +0000Collected Evidence: Collected Evidence: Restrict timing of lighting 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. BEHAVIOUR (0 STUDIES)Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1019https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1019Fri, 20 Dec 2013 17:59:19 +0000Collected Evidence: Collected Evidence: Use ultraviolet filters on lights One study evaluated the effects of using ultraviolet filters on lights on bat populations. The study was in the UK. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Abundance (1 study): One randomized, replicated, controlled study in the UK found that hedges lit with ultraviolet filtered lights had higher soprano pipistrelle, but not common pipistrelle activity (relative abundance) than hedges lit with unfiltered light. BEHAVIOUR (0 STUDIES)  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1020https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F1020Fri, 20 Dec 2013 18:00:18 +0000Collected Evidence: Collected Evidence: Avoid illumination of bat commuting routes Three studies evaluated the effects of avoiding the illumination of bat commuting routes on bat populations. Two studies were in the UK and one was in the Netherlands. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (3 STUDIES) Abundance (3 studies): One replicated, before-and-after study in the Netherlands found similar numbers of pond bats flying along unlit canals and canals illuminated with lamps. Two replicated, controlled studies in the UK found greater activity (relative abundance) of lesser horseshoe bats and myotis bats along unlit hedges than along hedges illuminated with street lights, but activity was similar for common and soprano pipistrelles and Nyctalus/Eptesicus species along unlit and illuminated hedges. BEHAVIOUR (2 STUDIES)      Behaviour change (2 studies): One replicated, before-and-after study in the Netherlands found that 28–96% of pond bats changed their flight paths along canals to avoid light spill from lamps. One replicated, controlled study in the UK found that lesser horseshoe bats were active earlier along unlit hedges than along those illuminated with street lights. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2017https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2017Wed, 05 Dec 2018 17:50:59 +0000Collected Evidence: Collected Evidence: Avoid illumination of bat foraging, drinking and swarming sites 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)Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2018https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2018Wed, 05 Dec 2018 17:52:42 +0000Collected Evidence: Collected Evidence: Direct lighting away from bat access points or habitats We found no studies that evaluated the effects of directing lighting away from bat access points or habitats on bat populations. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2019https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2019Wed, 05 Dec 2018 17:53:34 +0000Collected Evidence: Collected Evidence: Use 'warm white' rather than 'cool' LED lights We found no studies that evaluated the effects of using ‘warm white’ LED lights rather than ‘cool’ LED lights on bat populations. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2020https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2020Wed, 05 Dec 2018 18:01:53 +0000Collected Evidence: Collected Evidence: Use red lighting rather than other lighting colours Three studies evaluated the effects of red lighting on bat populations. Two studies were in the Netherlands and one was in the UK. 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. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2021https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2021Wed, 05 Dec 2018 18:06:28 +0000Collected Evidence: Collected Evidence: Use glazing treatments to reduce light spill from inside lit buildings We found no studies that evaluated the effects of using glazing treatments to prevent light spill from inside lit buildings on bat populations. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2022https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2022Wed, 05 Dec 2018 18:07:22 +0000
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What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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