Not just for Halloween- Why we should all protect bats.

Bats often get a bad press due to their associations with vampires and disease. However, people’s perceptions of them are often misjudged and they’re actually really important animals! This week I’ll be highlighting the reasons we need bats just as much as they need us!

So, first off let’s get some more background on them. There are over 1,400 bat species throughout the world, living in a wide range of regions from the Amazon rainforest to UK cities [1]. They use a variety of habitats for roosting, feeding and travelling. The roosts are where they sleep and can often change place throughout the year. Just like us, different species of bats have preferences to where they live, these can include caves, hollow trees, buildings and underground structures [2, 3]. At warmer times of the year, pregnant females can form maternity roosts, which help them keep warm and look after their ‘pups’ after birth. Bats usually forage where there’s lots of their food available such as in woodlands or over waterbodies. In the UK, all our bats only eat insects, although globally they’re known to also eat fruit, lizards and frogs [3]. They use commuting routes to travel between their roost and foraging site, these corridors are usually dark to protect themselves from predators.

Photo credit: IUCN

Bats are the only mammal capable of true flight thanks to their wings, which are actually made up of their fingers and live skin! This helps them manoeuvre through the air and catch their food with amazing precision. Many bats use echolocation which allows them to essentially see with sound, they send out calls (which are too high for us to hear), which reflect off objects. This echo can tell a bat all sorts of information about their prey, such as the direction and speed it’s flying, as well as its size. They can also use their call to choose their preferred meal!

Bats populations are declining, but why should we want to protect them? Even though their unique nature and unusual faces are enough motivation to want to conserve them, bats also help our environment in a number of ways.

Firstly, many a species are ‘bio-indicators’, meaning they are able to tell us about our natural environment [4]. This is because bats can be sensitive to changes such as habitat loss, climate change and even pesticide use. Therefore, decreases in bat populations can highlight an issue which may be affecting other species and is not obvious. Bats also eat massive amounts of insects, for example, the common pipistrelle (Pipistrellus pipistrellus) can eat 3,000 insects a night! They act as a pest-control, preventing damage to many plants and saving us from getting bitten by mosquitoes at night.

Photo credit: The Northern Echo

Although our UK bats don’t eat fruits and flowers, we are still impacted by those that do [5]. This is because they disperse seeds and pollinate the plants of our favourite foods and drinks, including chocolate and tequila! Therefore, without these bats we wouldn’t have the plants (and their products) which rely on them.

Protecting bats is really important, particularly now as their populations continue to decline. If we make small changes to our lifestyles such as turning lights off in unused rooms and closing curtains at night, we can help to reduce our impact on them! So, join the fight to turn off the light!

Next week I’ll be discussing the different bat species within the UK and to a much more local level, in Stoke Park.  

You can access information on this issue and find out how to help by following Blinded by the Night’s Facebook and Instagram pages. If you have any questions about the campaign or would like to get involved, please contact me via email at

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats


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Bats and Light Pollution

One of the major causes of global loss of biodiversity is artificial light at night (ALAN). ALAN refers to the use of artificial lighting that alters natural night-time light levels [1, 2, 3, 4].  Consequences of ALAN include the well documented reduction in visibility of stars in urban environments, pictured above [5]. Evidence indicates, however, that ecological impacts of artificial lighting are vast, and require urgent attention [4].

Figure 1: Hypothetical impacts of exposure to ALAN [6]

Light pollution affects the ecological interactions of a range of organisms (Fig. 1) by altering physiology, behaviour, reproduction and genetic fitness [4, 5, 7]:

What is Artificial Lighting?

Globally ALAN produces an estimated 1900 Mt of CO2 annually, consuming 19% of electricity produced [8]. Growing awareness of climate change and shifts in legislative policies have led to improvements in technology and efficiency, and less energy efficient traditional high and low pressure sodium bulbs are being replaced with broad spectrum light emitting diodes (LED) and ceramic metal halide lights [2,7]. LED lighting generally does not emit insect-attracting ultraviolet (UV) light, unlike metal halide lights and mercury vapour lights (Fig. 2), although LED lighting still attracts many invertebrates [9].

In the first half of the 20th century, ALAN increased worldwide by an average of 6% (range 2-20%); however, from 2012-2016 the global area impacted by ALAN increased by 2.2%, with radiance increasing at a similar rate [11]. Approximately half of Europe and a quarter of North America now experience a disrupted day/night cycle due to ALAN [11]. In the UK, over the last 50 years the energy efficiency of lighting has doubled, while the annual energy consumption for lighting has quadrupled [6, 12]. Only 46.2% of Britain still has pristine dark night skies, which equates to 21.7% in England, 56.9 in Wales, and 76.8% in Scotland [13].

How do bats respond to artificial lighting?

Responses to artificial light in bats are species-specific (fig. 3), believed to be due to flight morphology and echolocation [7]. Slow-flying species of bat such as Myotis spp. and Rhinolophus hipposideros tend to emerge longer after nightfall to avoid predators such as peregrine falcons [5] and so prefer to avoid lights. The light type and colour, habitat and bat activity also dictates the repsonse to light [14]

Figure 3: Genus specific responses to light. [Adapted from 15, 16]

Some bats may be attracted to artificial night lighting

Faster flying bats such as Pipistrellus spp. are better adapted in predator avoidance, often emerging before sunset [5, 7], and are more likely to be attracted to light sources as a result of insect light attraction (fig. 4) [17]. Tympanate moths (moths that have evolved organs with which to hear bat echolocation and take evasive action) attracted to light sources have been shown to reduce evasive behaviour under white light, making them easier prey for bats, which may cause competitive exclusion and increased competition with light avoidant bats foraging in nearby dark areas [7, 9, 18]. However, a study led by Dr Emma Stone found that despite bat and invertebrate activity being higher at white metal halide light compared to orange, fewer feeding buzzes were heard at these lights, suggesting the bats were not feeding as would be expected [7].

Figure 4: A row of street lights is exploited in different ways depending on genera, size, and wing shape. Nyctalus spp. are seldom seen at street lights, but have been observed utilising larger light sources such as floodlights © J. Eklöf [15]

Some bats have an aversion to artificial night lighting

A controlled study led by Dr Emma Stone in the South-West of England along 10 hedgerows measured the effect of three different light intensities using LED lights [2].  Findings of this study (figure 3) indicate that Myotis spp. activity was lower at all intensities compared to no light. R. hipposideros activity; however, was sequentially lower with higher intensities. Both species were observed to actively avoid the light, choosing to use the unlit side of the hedge; therefore, use of artificial lighting may result in interference with winter migration navigation and reduction in fitness from needing to travel further to forage [7].  

Figure 5. Geometric mean and confidence intervals of bat passes along the treatment hedge across LED treatments for (a) Rhinolophus hipposideros, (b) Myotis spp., (c) Pipistrellus pipistrellus, (d) Pipistrellus pygmaeus and (e) Nyctalus/Eptesicus spp. White bars indicate lit treatments. [2]

Despite the apparent attraction of Pipistrellus spp. to light, dark corridors appear to remain the preference for commuting [19].  Lighting outside roosts may prevent bats from leaving; a study at two bat roosts in Aberdeenshire indicated that fewer bats left the roosts when they were illuminated by white or blue halogen light compared to being unlit [20]. This delay in emergence results in fewer feeding opportunities and reduction in fitness [2].

Churches lit on all sides without provision of a dark corridor may prevent bats from roosting, or effectively entomb them to starve within their roosts [20, 22]

Other Effects of Artificial Night Lighting

Because of light avoidance, installation of new, inappropriate, or poorly researched lighting creates habitat fragmentation, driving away less light-tolerant bats, which impacts migration patterns, roosting opportunities, and genetic fitness. Sky glow caused by light reflecting off clouds makes bats more vulnerable to predators and obscures sunset, disorientating bats emerging from their roosts [17]. Even smaller light-tolerant bats such as Pipistrellus spp. are at risk of these consequences, and their increased foraging opportunities may in turn decrease the foraging opportunities of those who remain in the dark.

Further Information and Partners

Find your local bat group

Bat Conservation Trust

Bats and Lighting Research Project

Institution of Lighting Engineers

Bats in Churches


1. Stone, E., Jones, G., Harris, S. (2009) Street Lighting Disturbs Bats. Current Biology. 19, pp. 1123-1127.

2. Stone, E., Jones, G., Harris, S. (2012) Conserving energy at a cost to biodiversity? Impacts of LED lighting on bats. Global Change Biology. 18 (8), pp. 2458–2465

3. Zeale, M. R. K., Stone, E. L., Zeale, E., Browne, W. J., Harris, S., Jones, G. (2018) Experimentally manipulating light spectra reveals the importance of dark corridors for commuting bats. Global Change Biology. 24 (12), pp. 5909–5918

4. Hölker, F., Wolter, C., Perkin, E. K., Tockner, K. (2010) Light Pollution as a Biodiversity Threat. Trends in Ecology and Evolution. Vol. 25 (no. 12), pp. 681-682

5. Rich, C., Longcore, T. (2006) Ecological Consequences of Artificial Night Lighting. Island Press, Washington.

6. Hölker, F., Moss, T., Griefahn, B., Kloas, W., Voigt, C. C., Henckel, D., Hänel, A., Kappeler, P. M., Uhrlandt, D., Fischer, J., Klenke, R., Wolter, C., Tockner, K. (2010) The Dark Side of Light: A Transdisciplinary Research Agenda for Light Pollution Policy. Ecology and Society. 15(4).

7. Stone, E.L., Wakefield, A., Harris, S. and Jones, G. (2015) The impacts of new street light technologies: experimentally testing the effects on bats of changing from low-pressure sodium to white metal halide. Philosophical Transactions of the Royal Society B: Biological Sciences. 370 (1667), pp. 20140127

8. Organisation for Economic Co-operation and Development (OECD)/International Energy Agency (IEA) (2006) Light’s labour’s lost – policies for energy-efficient lighting. OECD/IEA, Paris, France

9. Wakefield, A., Broyles, M., Stone, E. L., Harris, S., Jones, G. (2017) Quantifying the Attractiveness of Broad-Spectrum Street Lights to Aerial Nocturnal Insects. Journal of Applied Ecology. 55, 714-722.

10. Gaston, K. J., Bennie, J., Davies, T. W., Hopkins, J. (2013) The Ecological Impacts of Nighttime Light Pollution: a Mechanistic Appraisal. Biol. Rev. 88, pp. 912-927.

11. Kyba, C. C. M., Kuester, T., de Miguel, A. S., Baugh, K., Jechow, A., Hölker, F., Bennie, J., Elvidge, C. D., Gaston, K. J., Guanter, L. (2017) Artificially lit surface of Earth at night increasing in radiance and extent. Science Advances. 3(11).

12. Fouquet, R., Pearson, P. (2006). Seven centuries of energy services: the price and use of light in the United Kingdom (1300-2000). The Energy Journal. 27, pp. 139-177.

13. Campaign to Protect Rural England (CPRE) (2003) Night Blight: Mapping England’s light pollution and dark skies. CPRE, London, England

14. Straka, T. M., Greif, S., Schultz, S., Goerlitz, H. R., Voigt, C. C. (2019) The effect of cave illumination on bats. Global Ecology and Conservation. 21.

15. Voigt, C. C., Azam, C, Dekker, J.,  Ferguson, J., Fritze, M.,  Gazaryan, S., Hölker, F., Jones, G., Leader, N., Lewanzik, D., Limpens, H. J. G. A., Mathews, F., Rydell, J., Schofield, H., Spoelstra, K., Zagmajster, M. (2018) Guidelines for consideration of bats in lighting projects. EUROBATS Publication Series No. 8. UNEP/EUROBATS Secretariat, Bonn, Germany, 62 pp.

16. Russ, J. (2012) British Bat Calls, A Guide to Species Identification. Reprint. Exeter, UK: Pelagic Publishing, 2019.

17. Mathews, F., Roche, N., Aughney, T., Jones, N., Day, J., Baker, J., Langton, S. (2015) Barriers and Benefits: implications of artificial night-lighting for the distribution of common bats in Britain and Ireland. Philosophical Transactions of the Royal Society B: Biological Sciences. 370: 20140124

18. van Langevelde, F., Ettema, J. A., Donners, M., WallisDeVries, M. F., groenendijk, D. (2011) Effect of Spectral Composition of Artificial Light on the Attraction of Moths. Biological Conservation. 144, pp. 2274-2281.

19. Hale, J. D., Fairbrass, A. J., Matthews, T. J., Davies, G., Saddler, J. P. (2015) The ecological impact of city lighting scenarios: exploring gap crossing thresholds for urban bats. Glob. Chang. Biol. 21 (7), pp. 2467-2478.

20. Downs, N., Beaton, V., Guest, J., Polanski, J., Robinson, S., Racey, P. (2003) The effects of illuminating the roost entrance on the emergence behaviour of Pipistrellus pygmaeus. Biological Conservation. 111 (2) pp: 247-252

21. Zeale, M. R. K., Bennitt, E., Newson, S., Pack-Man, C., Browne,  W. J.,  Harris,  S., Jones, G., Stone,  E. L. (2016):  Mitigating  the  impact  of  bats  in  historic  churches:  the  response   of   Natterer’s   bats   Myotis nattereri  to  artificial  roosts  and  deterrence. PLoS ONE. 11: e0146782

22. SwaloPhoto (2011) St Hilda’s Parish Church, The Headland, Hartlepool[photograph]. In: Flickr [online]. Available from: [Accessed 29 June 2020].

Introducing Blinded by the Night- Creating a community for humans and wildlife.

My name is Beth Gerrard and I’m a final year student studying Wildlife Ecology and Conservation Science at the University of the West England. Welcome to the first blog for my campaign, Blinded by the Night, which is running alongside the UWE Bat Conservation Research Lab. This campaign aims to protect bats around Stoke Park, Bristol through reducing light pollution.

I’m relatively new to blogging but think it can be such an important way to expand people’s knowledge on an issue. I will be posting these weekly and will cover a range of topics to let you really understand what’s going on and the simple ways in which you can help. I hope you find these informative and motivates you to get involved with a movement which can really make a difference!

So, what’s the problem?

Urbanisation is quickly expanding as we try to meet the requirements of our growing human population, resulting in large areas of habitat being converted into built-up, concrete areas [1]. For many wildlife this means their homes are separated creating small, isolated populations and light, air and noise pollution reduce the quality of their habitats. The barriers created mean animals such as hedgehogs and bats are either prevented from accessing their homes or need to take a longer, more energy-consuming route. Through making it harder for wildlife to survive, populations may decrease or if possible, move to more suitable homes. As well as affecting other species which rely on them, we are separating ourselves from the amazing variety of plants and animals we could be interacting with and makes our environment much duller!

Photo credit: Alamy

However, hope is not lost! Urban areas are filled with green spaces such as gardens, parks and even living walls! Nature is quick to adapt to our changes and much wildlife are able to thrive in urban environments. Despite this, we all need to play our part in reducing our impact on our wild neighbours.

Bats are particularly vulnerable to urbanisation due to the light pollution caused by Artificial Light At Night (ALAN). This is becoming more of a problem as artificial light is increasing by 6% each year! As bats are nocturnal, they are adapted to dark conditions, which means light night skies can affect their survival [2]. This doesn’t just impact bats, as they play an important role in helping the natural environment run smoothly, meaning other plants and animals will be affected. There are several bat species which rely on Stoke Park and the environment around. As it is surrounded by urban areas, much of which is residential, light pollution spills onto their habitats.

There’s a number of really simple things we can do at home to reduce our contribution to light pollution. Some of these include turning lights off in unused rooms, closing the curtains at night when the lights are on and using motion-sensor security lights [3]. However, this is just the start! Follow this campaign to see what else you can do to get involved and make a difference. You’ll soon realise that it’s not just bats and wildlife benefitting from these changes, as you can too! Reducing the light spilling from your home can attract a variety of interesting animals to your garden and save you money in the process.

Photo credit: Christian Giese

Thank you so much for taking the time to read this, I hope it’s provided you with some background to the issue and has sparked your interest in conserving bats! If you could, please complete this very short survey about your initial awareness of the issue, which also provides a variety of options you have in taking action. So, join the fight to turn off the light!

Next week’s blog will be focussing on why bats are so unique and need our protection, so make sure you give it a read!

You can access information on this issue and find out how to help by following Blinded by the Night’s Facebook and Instagram pages. If you have any questions about the campaign or would like to get involved, please contact me via email at

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats


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