4 min readNew DelhiUpdated: Jan 20, 2026 10:10 AM IST
A small municipality near Denmark’s Copenhagen has begun to install red-coloured streetlights along a stretch of road, which is known to be the habitat of several species of bats. Previously, the location had white lighting.
The development came after authorities at Gladsaxe Municipality determined that some bat species change their behaviour when they interact with artificial white lights.
Note that this is not the first time that the colour of streetlights has been changed to make them bat-friendly. In 2019, the Worcestershire County Council in the United Kingdom installed 60 metres of the glowing red lights in the area to ensure the well-being of bats.
Bats and lights
Over the years, several studies have indicated that white streetlights can pose problems for some species of bats.
For instance, a 2009 study, published in the journal Current Biology, found that bat species such as the lesser horseshoe bat avoid areas lit by white lights. This could be detrimental for them, as altering their routes would make bats vulnerable to attacks from predators.
A different study, published in 2017 in the journal Proceedings of the Royal Society B: Biological Sciences, revealed that forest-dwelling species like the long-eared bat and the mouse-eared bat avoid white and green lights. This could be because their eyes are highly sensitive to bright lights.
Also, “illuminating areas near a roost site can postpone, or even prevent, bats from emerging and, with nocturnal insect activity peaking at and just after dusk, a delay in feeding times can seriously affect bat health,” according to a report by The Guardian.
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These are the reasons why scientists and experts suggest that authorities should not place bright lights near the feeding areas and roosting sites of bats.
As a result, authorities have been placing red lights in such areas. The 2017 analysis — in which researchers studied bat activity under experimental white, green and red LED-light conditions — stated that the long-eared bat and the mouse-eared bat do not change their behaviour in red light.
Kamiel Spoelstra, a co-author of the study, told Phys.org, “The lack of effect of red light on both the rarer, light-shy species and the more common non-light-shy bats… [This] opens up possibilities for limiting the disruption caused by external, artificial lighting in natural areas, in situations where having light is considered desirable.”
Significance of bats
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Bats play a crucial role in the ecosystem. For example, PO Nameer, the head of the Department of Wildlife Science at College of Forestry, Thrissur, had told The Indian Express in 2023, “Fruit-eating bats help in seed dispersal and pollination. Trees and plants that are bad pollinators themselves depend on them.”
On the other hand, there are insect-eating bats which feed on insects that are harmful to humans.
However, loss of habitat, global warming and human encroachment have emerged as a severe threat to many bat species across the world. Also, after scientists found that SARS-CoV-2, the pathogen behind the Covid pandemic, was part of a family of viruses found in some horseshoe bats, several communities and government authorities launched a crusade to kill bats. This happened even though scientists have yet to determine how the bat infected its first victim.
