Bats and lighting: activity does not mean no impact

Technical summary · Updated 28 October 2026

What the research found

Spoelstra and colleagues (2017) tested different light spectra at eight field sites. Myotis and Plecotus bats avoided white and green lighting, while Pipistrellus activity increased around those lights. Responses to red lighting were closer to the dark controls for these groups. The experiment shows that responses differ between species and lighting conditions.

How to interpret it

More activity around a lamp can reflect insects concentrating there. It does not demonstrate that the lighting benefits all bats or leaves their wider habitat unaffected. Equally, the study is not a universal guarantee that any red lamp is harmless: intensity, duration, position and the ecological setting still matter.

The design implication

Identify roost access points and the routes connecting feeding habitats before fixing a lighting layout. Retaining darkness is the starting point. Where lighting is necessary, work with an ecologist and lighting designer to control spill and operating periods, using current ILP/BCT guidance. Assess habitat connections as well as individual trees or buildings.

Sources & further reading

This is an explanatory summary of the cited evidence, not an original research paper or a site-specific survey specification.