Use ultraviolet filters on lights

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

45%
Certainty

22%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Ultraviolet filters may be fitted to existing lights to filter out the ultraviolet component and reduce the attraction of insects and foraging bats. For similar interventions, see ‘Use ‘warm white’ rather than ‘cool’ LED lights’ and ‘Use red lighting rather than other lighting colours’.

Study locations

Key messages

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 UKfound 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)

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, controlled study in 2014 at five hedges in Devon, UK (Mathews et al 2015) found that hedges lit with ultraviolet (UV) filtered lights had higher activity for one of two bat species than at hedges lit with unfiltered lights or unlit hedges. Soprano pipistrelle Pipistrellus pygmaeus activity was higher at hedges lit with UV filtered lights (average 5 bat passes/night) than at hedges lit with unfiltered lights (3 bat passes/night) or at unlit hedges (4 bat passes/night). Common pipistrelle Pipistrellus pipistrellus activity did not differ significantly between any of the light treatments (data not reported). At each of five hedges, two lights (8W LED flood lamps with additional UV bulbs) were set up 15 m apart and 5 m high. Filtered lights were covered with UV film filters to reduce UV emissions by 40%. Three treatments (UV filtered lights, unfiltered lights, unlit/control) were carried out at each pair of lights in a random order for three nights each between July and October 2014. Two additional unlit locations were also surveyed at each site. During each night, bat activity was recorded using bat detectors placed at the treatment site and at the unlit locations for 3 h from sunset.
Study and other actions tested
Referenced paper
Mathews F., Gaston K., Bennie J., Day J., Schofield H. & Baker J. (2015) The biodiversity impacts of street lighting. Appendix G: An experimental test of a mitigation strategy to reduce the impacts of lighting on bats. DEFRA report, WC1011.

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?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Bat Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Direct lighting away from bat access points or habitats Action Link	No evidence found (no assessment)	0	Synopsis Link
Avoid illumination of bat foraging, drinking and swarming sites Action Link	Likely to be beneficial	2	Synopsis Link
Use glazing treatments to reduce light spill from inside lit buildings Action Link	No evidence found (no assessment)	0	Synopsis Link