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Bat radio-tracking in Somerset – interns needed!

Summer 2021: The UWE Bat Lab is conducting a greater horseshoe bat radio-tracking study from August-September and needs assistance!

We’re after one or two interns who can commit 6 weeks to the project from mid-August. Interns will gain extensive experience radio-tracking and locating roosts. Interns will also have the chance to get involved in trapping and gain experience handling bats and taking biometrics.

Previous radio-tracking experience is not essential as full training will be provided. Own transport is essential. Work will involve tracking bats all night from dusk until dawn. Tracking will be centred around a number of roost sites in North Somerset, Bath and North-East Somerset and Mendip District, Somerset.

Tracking work is part of ongoing research in the lab, we’re gathering data to ground-validate spatial models of habitat suitability and landscape connectivity that are being developed for Natural England. Models will give Natural England a detailed understanding of how greater horseshoe bats use the landscape across Somerset and will be used to inform local planning and development decisions, to minimise the impact of development on greater horseshoe bats.

If you’re interested please get in touch with your availability: thomas.foxley@uwe.ac.uk.

A ‘brighter’ future- Summary of campaign and future directions for bat conservation.

This is my final blog and I hope you have enjoyed reading these as much as I have loved writing them! Over the last few months, I’ve covered a range of topics regarding the impacts of light pollution on bats and suggesting ways you can help. As you will now be aware, our UK bats are being seriously threatened by urbanisation through habitat loss and increased Artificial Light At Night (ALAN). It’s in all of our interests to ensure we halt the declines in bat populations by playing our part in reducing our impacts.

Brown long-eared bat in roost copyright Echoes Ecology Ltd 2016 -  BatAbility Courses & Tuition

Photo credit: Echoes Ecology Ltd.

Through following some of the tips we’ve suggested you can massively reduce light pollution coming from both inside and outside your house. Switching to Light-emitting Diode (LED) lamps, turning your lights off and considering whether a light is actually needed, are all ways you can limit this issue, whilst saving you money! Resources, such as print-out prompt templates, are available on our Facebook page to help you change your habits and help you remember to turn off your lights. Making small changes at home is such an easy way to make a big difference! If you want to make even more of an impact, contacting your local council and businesses will help to improve existing lights and prevent new developments from becoming big sources of light pollution.

Despite often (and wrongly!) being viewed as pests, bats are such important animals, helping both our natural ecosystems and acting as pest control in our gardens. I hope this campaign has allowed you to realise how amazing these flying mammals are and motivated you to support them, through both altering your lights and starting conversations with your friends and family. Through our work with South Gloucestershire Council and UWE, we also hope you’ve been able to realise how open people are to help, which may have encouraged you to start your own bat conservation projects!

Thank you to everyone who has got involved with Blinded by the Night’s work and enabled these changes to be made! As urbanisation continues to increase, we all need to make sure we carry on implementing change to give bats the best chance of adapting and thriving to these new environments. Despite finishing these blogs, Blinded by the Night will continue to work with local businesses and councils to ensure we reduce light pollution around 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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

Celebrating success- What we’ve been up to.

The first couple of months of this campaign have been very busy and we think we’ve made some great progress! My previous blogs have focused on what you can do to help, so this week I thought I’d focus on what Blinded by the Night have been up to.

Blinded by the Night have been working with three stakeholders, who we think will be able to make the biggest difference in protecting bats around Stoke Park. Our first is you, the public, particularly those who live around Stoke Park and Bristol! In an initial awareness survey almost 75% of you said that you were aware that artificial lighting can negatively impact bats, which was an amazing start! In our follow-up survey a few weeks later, this increased to 92% of you, which is even better! Another exciting achievement was organising an online event alongside Bristol’s Bats and Bristol Nature Network. We hosted two expert speakers, Dr Emma Stone from the University of the West of England (UWE) and Jo Ferguson from the Bat Conservation Trust (BCT). The talks focused on the impacts of light pollution on bats and suggested several ways in which you can help. We had a great turn out, even selling out and being attended by a top researcher in the field! If you weren’t able to make it to the event, a recording is available on YouTube via this link: https://www.youtube.com/watch?v=tyrTK9aT1SA

Photo credit: Northumberland Bat Group

More successful efforts came from reaching out to UWE’s Frenchay Campus, located right next to Stoke Park, to see whether any changes could be made to their lighting in the hope of reducing its impact on bats. UWE’s Energy Projects Manager, Melissa Clarke, agreed to meet with me and discuss the lighting scheme around campus. From this, we highlighted priority areas to focus conservation efforts on and I later developed some suggestions based on our discussion. I was really pleased to hear that these had been reviewed and sent to various members of staff around UWE. Blinded by the Night have been told that our lighting recommendations have been considered for the new campus accommodation, which will hopefully be implemented and benefit Stoke Park’s bats. We feel our efforts here have been successful and welcomed by UWE, who are clearly invested in biodiversity and sustainability and we look forward to continuing working with them to protect bats!

One of the biggest achievements of this campaign has been from our work with South Gloucestershire Council. Following on from meetings with their Electrical and Building Maintenance Manager, South Gloucestershire Council have agreed to switch their current streetlights to Light-emitting Diode (LED) lamps along Long Down Avenue (next to Stoke Park’s woodland). With this, light spill will massively be reduced, limiting how much shines into important bat habitats. The lights will also be dimmed throughout the night, meaning they aren’t brighter than they need to be. Additionally, upon approval of funding that we have applied for, an ecological survey of bat activity will be conducted over summer to assess the impacts of the streetlighting before and after LED installation. This will provide insight into the effects of different light types on bats and has potential to influence future lighting policies within the area!

Despite only starting a couple of months ago, Blinded by the Night has been able to engage with several stakeholders who share the same concern we do for our declining bats. We have been able to make some positive steps in significantly reducing light pollution around Stoke Park, which will no doubt benefit our local bats!

Next week is my final blog! I’ll be summarising our campaign and discussing the future directions of bat conservation in relation to our increasingly urbanised landscapes.

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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

Everyone’s a winner- How you can benefit from supporting bats.

As much as we all care about conserving bats, our busy lives might mean that sometimes we need a bit of an incentive to motivate us into making a change! Today I’ll be highlighting some of the ways you can benefit from helping protect our bats. If you haven’t already, it may be worth giving last week’s blog a quick read before continuing here to see the different ways you can help make a difference. So, let’s begin!

An easy way to make a big difference is by switching to Light-emitting Diode (LED) lamps in and around your home. These can help you save money in a couple of ways. Firstly, LEDs last much longer than other household lamps, with an average lifetime of 20,000 hours, although some last up to 60,000 hours [1, 2]. Whereas incandescent lamps last around 1,000 hours and halogen 2,000 [2, 3]! This means you’ll have to replace your incandescent bulb 20 times and halogen 10, during the lifetime of one LED bulb!

Photo credit: Arcadia

LEDs are also much more efficient, meaning they use less energy. For example, a 5 watt LED is equivalent to a 40 watt incandescent bulb, and a 7.5 watt LED to a 50 watt halogen bulb, using 87.5% and 85% less energy respectively [2, 4]. Not only is this great for the environment, as switching all bulbs to LEDs in your home can save 63 kg of carbon dioxide a year, but also for your wallet [5]! Over a 20,000-hour lifetime, the replacement and energy costs of one LED bulb is £24.40, whereas incandescent bulbs would cost £153.40 over the same period [2]. This means changing eight lights to LEDs in your home would save you £1,227!

LEDs are also much safer bulbs as they don’t produce heat or break easily meaning replacing them shouldn’t cause issues [1]. Unlike bulbs such as Compact Fluorescent Lamps (CFLs), they don’t contain any harmful materials, such as mercury, making them safer for you and the environment [1]!

Photo credit: Alex Lang

So now you’ve seen the clear economic benefits of using LEDs, how can you benefit from them in relation to bats?

As LEDs don’t emit UV, using them for outdoor lighting won’t attract large amounts of insects to your garden! Although, make sure you use a ‘warm’ lamp (less than 2700 K), as ‘cool’ and blue light can still lead to clusters! As urbanisation is increasing, gardens have become havens for many wildlife, which use them for food and shelter [6]. Reducing light pollution in your garden, as well as planting lots of different flowers, can attract a variety of wildlife! You’ll be helping many native animals thrive but also making your home a much more interesting place. Attracting nocturnal animals to your garden, such as bats and hedgehogs, provides you with free pest control and insect repellent! This is because they eat common plant pests as well as huge amounts of mosquitoes, stopping you from getting bitten!

Hopefully you can see that it’s not just bats benefitting from the changes you’re making. You can save money and make your garden an urban oasis, which supports a variety of native wildlife. Everyone really is a winner!

Next week I’ll be going over some exciting things which have been going on in our campaign!

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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

References:

  1. URL: https://www.renewableenergyhub.co.uk/main/led-lighting-information/residential-led-lighting/
  2. URL: https://www.simplyled.co.uk/info/led-savings/
  3. URL: https://usa.flos.com/blog/how-to-choose-led-vs-halogen-lights#:~:text=LED%20bulbs%20can%20use%20as,LED%20bulbs%20are%20generally%20shatterproof.
  4. URL: https://ledhut.co.uk/blogs/news/led-vs-halogen-is-led-or-halogen-better
  5. URL: https://energysavingtrust.org.uk/getting-best-out-your-led-lighting/
  6. URL: https://www.bats.org.uk/advice/gardening-for-bats 

Small changes, big differences- How you can get involved.

As it’s starting to get warmer, many bats are slowly coming out of hibernation meaning we all need to make sure we are doing everything we can to reduce light pollution. My previous blogs have briefly mentioned ways in which you can help protect our bats. So, I thought it would be a good idea to summarise all the things you can do in one blog so you can refer back to it whenever needed!

What can you do at home? Reducing light pollution coming from your home is a great place to start! There’s so many small and simple changes you can make, which can make a big difference! Firstly (and probably the most obvious), is to turn off your lights when you’re not using them. It’s such an easy habit to leave a room without pressing the switch, but through creating prompts to put by your lights or getting someone to remind you, you can start to change that (free printout templates are available via the campaign Facebook page). Another way to reduce the light spilling from your home is to dim the lights (if possible) to reduce the intensity of it, plus who doesn’t love a bit of mood lighting?! Changing your actual light bulb can benefit bats and other wildlife too. Using a light which doesn’t emit UV (or has a UV-blocking filter), as well as having a ‘warm’ colour temperature (ideally under 2700 K) can be really beneficial. Light-emitting Diodes (LEDs) are a great solution for this and are becoming increasingly popular, they also have a much lower wattage than other bulb types, which is great for reducing light’s intensity and saving money!

Photo credit: Geza Farka/ Shuttercock

Even the most bat-friendly lights can still spill out of your windows and contribute to a ‘sky glow’. Therefore, it’s important to make sure you close your curtains at night (when bats are out and the light’s glare is brightest). Choosing thick curtains or blackout blinds are most preferable as this massively limits how much light actually spills out of your windows.

Outdoor security and garden lighting can cause big problems for bats as they attract insects and spill into bat habitats more easily. Minimising your outdoor lighting can be really beneficial through using the suggested light bulbs and considering whether all of them are actually needed. Using candles can be a great idea if you want to keep the aesthetics whilst massively reducing your impact. It may be that switching outside lights off isn’t an option, in which case making sure they are facing downwards and away from any vegetation (especially where roosts are suspected) is vital! Directing light downwards can also be achieved through installing accessories to your light fittings such as hoods or baffles. If you use security lights, making sure they are fitted with a motion-sensor and timer (around 1 minute) can keep you feeling safe without having to keep your lights on all night. Planting dense vegetation or a solid fence/wall around your garden can help to limit the light spilling out.

Fighting light pollution and conserving bats doesn’t just need to happen within your home! There’s loads of opportunities to get involved such as joining your local bat monitoring group to survey and identify bats within your area. You can also encourage your community to join in through starting conversations with your family and friends about the impacts of light pollution on bats (you’d be surprised how willing people are to help)! Sharing your knowledge with others through creating leaflets and posters to put up around your area can also engage a much larger group of people.

Photo credit: Bat Conservation Trust

Developing people’s awareness of the issue is so important when driving change but we also need support from our local businesses and council. Contacting them to address the issue and ask what they are doing to help will bring the problem to their attention. Suggesting actions such as altering their security and streetlighting regimes, as well as developing dark corridors for bats, can help target specific issues. If enough people do this, they are more likely to prioritise these concerns and bring about change!

I hope reading this has sparked some ideas about how you can help and allowed you to realise a variety of things you can do. Making small changes to the way we use lights around our homes can have such a big difference to bats. Light pollution has a huge impact on so much wildlife yet can be easily reduced, we just need to know how!

Next week I’ll be covering how your efforts in bat conservation can benefit yourselves, which will hopefully encourage you to continue to the fight to turn off the light!

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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

Lighting the way- The impacts of light pollution on bat commuting behaviour.

This week is my last slightly sciencey blog focusing on the different bat behaviours impacted by light pollution! I will have covered three major areas, but it’s important to know that light’s effect extends to other aspects of bats’ lives. Although understanding the impacts on foraging, roosting and commuting will give you a good grasp of the issue and allow you to make informed choices about your lighting.

How does artificial light affect bat commuting?

Bats commute between their roosts and foraging sites using a network of routes [1]. These are often linear and consist of a variety of features including gardens, woodland edges, waterways, rows of street trees and hedgerows [1, 2]. Commuting routes are important as it helps bats to navigate their way around and acts as a form of protection against bad weather and predators [1]. Bats often use the most efficient route to maximise their foraging time and minimise energy losses [1]. However, if light spills onto a commuting route the network can become fragmented, causing a variety of responses and knock-on effects [1, 3].

Photo credit: Emma Stone

One response recorded is avoidance, as many bats will turn away from a light source and may fly back to their roost [4]. This can mean the availability of foraging sites are reduced, limiting how much food and energy they can gather. Returning to their roost without feeding can also negatively impact bats, as they waste unnecessary energy flying to and from [3].

Another response adopted by many bats is using an alternative route, which can have several negative consequences [1, 3]. Firstly, these routes may be longer, meaning they spend more time flying and less time foraging, resulting in fewer insects eaten [1]. Arriving at the foraging site later may also mean bats miss the peak prey abundance, having to rely on suboptimal or less food [3]. The less energy gained along with higher energy costs from flying further and increased stress levels can reduce the fitness of bats [4]. This can then lead to reduced reproductive success, meaning lighting of commuting routes during their reproductive period can be particularly serious due to their high energy requirements [3, 4].   Alternative routes can also provide less vegetation cover, which can expose bats to predators and bad weather, increasing both their predation risk and energy costs [1, 3]. If bats perceive the energy costs too high, they may be cut off from their foraging site and left without an alternative [3]. This can be really serious for bats’ survival, as they may be forced to abandon their roost, causing further damage to the overall functioning of the ecosystem [1].

Photo credit: Graham Horn

Certain bat species rely on these routes more than others. For example, slow flying bats, such as horseshoes (Rhinolophus) and Myotis species, are more vulnerable to predators in open spaces, meaning commuting routes are an important source of protection [2, 5]. Even low levels of light can impact them, with activity levels of the rare lesser horseshoe (Rhinolophus hipposideros) reducing at only 3.6 lux (lower than side street lighting) [5, 6].  Faster flying bats including Pipistrellus, Nyctalus and Eptesicus species have been found to either be unaffected or benefit from lighting on routes [7]. As mentioned in my previous blog on foraging, slow flying bats are more light-sensitive meaning the combined effects of reduced foraging and fragmented commuting routes can have more serious implications.

If you live close to an area which you suspect may be a suitable commuting route, it’s important to try to avoid lighting falling onto or even around it, as our more vulnerable bats can be very sensitive to low brightness levels! An effective way to improve bat commuting routes is by contacting your local council to suggest changing to more bat-friendly lights near dark corridors or even creating a corridor! This could include low level lighting or motion-sensor lights to limit the time they are switched on for.

Next week, I’ll be moving away from the impacts of lighting and suggesting to you a variety of ways you can help to make a big difference!

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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

References:

  1. URL: https://cdn.bats.org.uk/pdf/Bats_and_Lighting_-_Overview_of_evidence_and_mitigation_-_2014_UPDATE.pdf
  2. URL: https://www.researchgate.net/publication/272889669_Impacts_of_artificial_lighting_on_bats_A_review_of_challenges_and_solutions
  3. URL: https://www.sciencedirect.com/science/article/pii/S0960982209011932
  4. URL: https://arnhemspeil.nl/docs/2008-07-10-vzz-experimental-evidence-of-light-disturbance-along-the-commuting-routes-of-pond-bats.pdf
  5. URL: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2012.02705.x
  6. URL: https://cdn.bats.org.uk/pdf/Resources/ilp-guidance-note-8-bats-and-artificial-lighting-compressed.pdf?mtime=20181113114229&focal=none
  7. URL: https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14462

Letting the light in- How lighting can impact bat roosting.

Last week I started going into more detail about how light pollution impacts bat behaviour, specifically foraging. I hope it allowed you to see the complexity of the issue and left you wanting to know more. If so, you’re in luck! Today I’ll be going over how artificial light can affect the roosting behaviour of bats and a few simple ways you can help.

Roosts are where bats shelter (often in groups) and can vary lots in structure, with tree hollows, building roofs and underground caves all being used. Locations change regularly depending on the time of day, season and purpose to suit their requirements (wouldn’t you if it were free?!) [1]. For example, the maternity roost, where females gather to give birth and raise their young, will be different to their hibernation roost, where they rest throughout winter [2].

Roosts are really important habitats for bats, so much so that they’re protected in the UK, meaning it’s an offence to disturb or destroy them [1]. Due to its negative impact on bats, artificial light that falls directly onto a roost is actually classed as a disturbance!

Photo credit: Lindsay Carrington Ecological Services

So how does light affect bat roosting?

Roosts located in illuminated areas can delay bat emergence and prolong its duration [1, 3]. For example, a study on the effects of illuminated buildings on house-dwelling Geoffroy’s bats (Myotis emarginatus) found that the majority of the colony didn’t emerge until full darkness, with earlier emergence only returning two days after the lights had been disconnected [3]. Not only does this show that light delays emergence times, but also that some species can be slow to recover. Delayed emergence negatively impacts bats through reducing their foraging times and causing them to miss peak prey abundance, meaning they gather less food and have to rely on suboptimal prey [4, 1].

So, what does this mean?

This can impact bats individually, as reduced fitness can make them more susceptible to other threats [1]. However, the whole colony can also be compromised with problems arising such as reduced reproductive success and juvenile growth rates [1, 3]. For example, a study found that juveniles in an illuminated maternity roost were significantly smaller than those in dark roosts [5]. This is because juveniles rely on their lactating mothers who cannot gather enough food when their emergence is delayed.

As well as being at a disadvantage to larger juveniles, their lower body mass reduces their hibernation success as they have less fat stored [3]. Considering bats’ long lives and slow reproduction, populations impacted by reduced juvenile growth can take a long time to recover and have serious conservation implications! Light can also impact hibernation, as bats have been known to avoid these roosts in lit areas, which can impact their ability to survive [4]. Additionally, light spilling onto a hibernation roost can wake bats up, meaning they are wasting unnecessary energy [4].

Photo credit: CyberKat/Shuttercock

Artificial lighting around roosts can also force bats to change which entrance/exit they use [1]. These may be suboptimal, impacting their habitat connectivity and increasing mortality rates. This is because alternative exits can lead bats into exposed areas such as open spaces, roads and ground level, where predation and collision risk are higher [1].

As well as effecting the survival abilities of bats, long-term and direct light exposure onto a roost can actually lead to bats becoming entombed or abandoning them [1, 4]. This can result in sudden drops in populations, for example, numbers of little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus) dropped by 53-89% and 41-96% after light installation inside a nursey roost [6]. But that’s not even the worst of it! Research found that direct illumination onto a maternity roost of Geoffroy’s bats caused all 1,000-1,200 females to abandon it [3]!

How can we help?

Light pollution can impact roosting in so many ways and it’s evident that it can have some really serious consequences. Lights should never spill directly onto a roost and ideally the areas surrounding them. If you’re aware of a bat roost near to your home, making sure there’s as little light as possible surrounding it is really important. An easy way to do this is by positioning your lights to face away from the site and if you’re able to, place something like dense vegetation between the roost and light to lower the intensity. You could also install a bat box in a safe area of your garden which does not become illuminated at night! As roosts are so important to bat conservation, making small changes to lighting around your home (especially outside) can be a big help!

Next week will be the last blog which focuses on the impacts of light pollution on bats, specifically commuting!

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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

References:

  1. URL: https://cdn.bats.org.uk/pdf/Bats_and_Lighting_-_Overview_of_evidence_and_mitigation_-_2014_UPDATE.pdf
  2. URL: https://www.researchgate.net/publication/242604931_Importance_of_night_roosts_for_bat_conservation_Roosting_behaviour_of_the_lesser_horseshoe_bat_Rhinolophus_hipposideros
  3. URL: https://www.researchgate.net/publication/232683086_The_effects_of_the_illumination_of_buildings_on_house-dwelling_bats_and_its_conservation_consequences
  4. URL: https://www.researchgate.net/publication/272889669_Impacts_of_artificial_lighting_on_bats_A_review_of_challenges_and_solutions
  5. URL: https://www.sciencedirect.com/science/article/pii/S0006320702002987
  6. URL: https://www.jstor.org/stable/3799798?origin=crossref&seq=1

Not all ‘bats’ are created equal- The impacts of light pollution on bat foraging.

Understanding exactly how bats are impacted by light is really important as it can put into context the difference your efforts are making! Artificial light can affect several bat behaviours and as a result, impact their survival. This week I’ll be discussing how light alters the foraging behaviour of different bat species and their prey.    

All our UK bats eat insects. Most eat very small bugs such as mosquitoes and midges, but they are also known to munch on larger insects including moths and beetles [1]. Bats forage where prey is most abundant, such as pastures, ponds and woodland [1]. But what happens when insects gather at a light?

As mentioned last week, Ultraviolet (UV) and blue-white light emitting lamps attract many species of insect [2]. At first, this sounds great for bats, and for some it is! However, as different bats feed in different ways some species are much more light-sensitive than others. This means only light-tolerant bats will take advantage of the insect clusters at a light source. These are usually fast-flying bats which are adapted to forage in large, open spaces [2]. For example, the common pipistrelle (Pipistrellus pipistrellus), soprano pipistrelle (Pipistrellus pygmaeus) and noctule (Nyctalus noctula) have all been recorded foraging at streetlights [2].

Photo credit: Forschungsverbund Berlin e.V (FVB)

As larger moths are more attracted to short-wavelength (UV/blue) light than smaller moths, light-tolerant bats can gain more energy much quicker, meaning they can forage for less time and reserve energy [3]. This means they have a competitive advantage over light-sensitive species. It has been suggested that some bat species have already evolved to forage at a light source. For example, in southern Europe, the Kuhl’s pipistrelle (Pipistrellus kuhlii) is thought to have adapted the morphology of its skull to eat larger moths [4]! However, despite the obvious benefits for light-tolerant bats, they too can be negatively impacted. Bats are sensitive to UV lights as it can damage their eyes, meaning those which spend lots of time feeding at a light may have reduced eyesight over time [4]. This is concerning considering the long lifespan many bats have, particularly for Nyctalus species which travel long distances and need to be able to navigate. Additionally, feeding at a light source can increase the mortality rate for bats as vehicle-collision and predation risk increases, especially for juveniles which are slower [2].

So, what about the light-sensitive bats?

As may have guessed, they will avoid the light, even if there’s an abundance of insects at it. Their sensitivity is thought to be a result of their slower flight and later emergence times for reducing predation [4]. This means many species, such as brown long-eared bats (Plecotus auritus) and Natterer’s bats (Myotis nattereri), will lose foraging areas to artificial light [2]. A ‘vacuum effect’ can also occur, which is where insects are attracted away from dark areas towards a light [3]. This can be really serious for light-sensitive bats as they will struggle to find food in their dark foraging spots. This means they will have to fly further (using more energy) to find food or must rely on suboptimal prey [1]. Reduced foraging opportunities mean light-sensitive bats may be out-competed by light-tolerant bats and they may suffer from long-term effects such as reduced juvenile growth rates [1]. The morphology of light-sensitive species has been associated with a higher extinction risk, meaning conserving them and reducing our impact on them is even more of a priority!

Photo credit: Eleonimages/Shuttercock

As well as affecting bats’ foraging behaviour, artificial light largely impacts their prey. In fact, it is considered to be a main driver in the insect biodiversity crisis [3]. Attracting insects to a light source increases their mortality rate in various ways. First of all, lights can be confused for the moon, which they use for orientation, meaning they will fly around the lamp until they eventually die of exhaustion or collision with the hot bulb [3]. Diverting insects away from important activities such as foraging or mating can also cause survival problems [4]. Insects’ risk of predation also largely increases because of artificial light. For example, they can be ‘dazzled’ by the light meaning they are immobilised and rest on the ground or vegetation allowing for predators to easily find them [3]. As mentioned earlier, as they cluster at light, insects are easy prey for light-tolerant bats, which leads to disproportionate amounts being killed. This can seriously impact insect populations and reduce food availability for light-sensitive bats, disadvantaging them even more [2]!

Additionally, as certain species of insects are attracted more than others, the high mortality at lights will alter the composition of insect communities [2]. For example, predatory insects are more attracted to High Pressure Sodium lamps (HPS), meaning if large quantities of them die there will be an increase in their prey populations, which will have knock-on effects for the whole ecosystem [1]. Finally, the ‘vacuum effect’ can result in local extinction of insects which are drawn away from their natural ecosystem [3]. As well as being massively disruptive to insect communities, many species which rely on them will be affected. This of course, includes bats, particularly light-sensitive species, which can be largely impacted even by local reductions in prey [1].  

As you can clearly see, light pollution impacts bat foraging in lots of different ways! As well as creating competition between species, artificial light affects bats through altering their food availability. It’s so important we ensure we’re all limiting our contribution to the issue. In terms of minimising changes in foraging behaviour, we can reduce our outside lighting, making sure it is only on when needed and switching to non-UV emitting, ‘warm’ lamps. Contacting your local council about switching to more bat-friendly streetlights can also make a massive difference!

Next week I’ll be continuing to explain the effects of light pollution on bat behaviours, focusing on roosting!

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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

References:

  1. URL: https://cdn.bats.org.uk/pdf/Bats_and_Lighting_-_Overview_of_evidence_and_mitigation_-_2014_UPDATE.pdf
  2. URL: https://www.researchgate.net/publication/272889669_Impacts_of_artificial_lighting_on_bats_A_review_of_challenges_and_solutions#pf7
  3. URL: https://link.springer.com/chapter/10.1007/978-3-319-25220-9_7
  4. URL: https://royalsocietypublishing.org/doi/10.1098/rstb.2014.0124

Shining a light on…light! – Different light types and their impacts.

Through reading my previous blogs you’ve now probably got a pretty good idea of how amazing and important bats are. Over the next few weeks, I’ll be going into a bit more detail about exactly how light impacts bats, so you know what to look out for when fighting light pollution! Today I’ll be briefly covering how various types of light affect bats in different ways.

First of all, it’s important to understand how light types differ from each other. Light travels in waves of different lengths and frequencies. The electromagnetic spectrum is a range of all these waves, most of which we can’t see. The wavelengths between 380-780 nm (nanometres) can been seen by humans and are known as ‘visible light’ [1]. Each colour we see has a specific wavelength which falls within this boundary. Most other plants and animals, including insects and snakes, can detect light outside of our spectral range, such as ultraviolet (UV) and infrared [2].

Photo credit: Cole-Palmer

We use a variety of light types which emit different wavelengths as a result of the materials used in the lamps [2]. Those which emit large amounts of invisible light are considered inefficient, as lots of energy is being wasted meaning more is required to achieve the brightness we want. As well as wasting energy, UV-emitting lights can attract animals which see it, causing many of them, largely insects, to cluster at a light source. Another issue is the colour ‘temperature’ of the light, as bats have been shown to be more sensitive to ‘cool’ blue lights [3]. The temperature of a light is measured in degrees Kelvin (K), with ratings below 3200 K considered to be ‘warm’ and those above 4000 k considered ‘cool’, which attracts insects [1, 4].

Photo credit: Power Outage Lights

So, what does this mean for bats?

As they eat insects, clusters at a light source will also attract light-tolerant bats, such as pipistrelles. This means they will have a competitive advantage over light-sensitive species, such as the Daubenton’s bat (Myotis daubentonii), which avoid the area. UV lights can also damage bats’ eyes, meaning over time they will struggle with navigation [3]. This is particularly worrying as some bats can live up to 30 years!

We’re all becoming a lot more aware of climate change, meaning many lights, both in our homes and on streets, are changing to become more efficient through emitting more visible light. This means the spectral composition and temperature of them are changing. For example, incandescent lamps were traditionally used for domestic lighting, although they are ‘warm’, they are being phased out as they emit lots of invisible infrared light [2]. Compact Fluorescent Lamps (CFL), Light Emitting-Diodes (LED) and Halogen lamps are replacing incandescent lamps [5]. However, CFLs and Halogen lights both emit UV, which if located outside or spill out of your windows, can negatively impact bats [6]. All three lamps are available in different colour temperatures, meaning those which emit ‘cool’ light can also impact bats.

Which lighting should you choose for your home?

It’s important you choose a light which doesn’t emit UV or ‘cool’ light. This is particularly important for any lights used outside for security or in the garden, as they contrast more with the night sky. LEDs are really efficient and are becoming increasingly popular, they don’t emit UV meaning they’re much more suitable than other modern lighting. Through using non-UV-emitting lights you can also save money as less energy is being put into making invisible light. However, if you don’t want to change your lights too much, UV-blocking glass and accessories are available for UV-emitting lights, to reduce how much spreads. Making sure you use a ‘warm’ bulb is also really important; these should be below 3200 K but ideally, to have minimal impact on bats, below 2700 K.

I hope I’ve helped you understand a bit more about how different lighting has different effects on both bat and other wildlife. It’s important to understand what the problem is so we know how to make changes which have a big impact!

Next week I’ll be going into more detail about how light affects the foraging behaviour of bats!

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 Beth2.Gerrard@live.uwe.ac.uk.

How to get involved:

Facebook: Blinded by the Night @blindedbythenightbristol

Instagram: @blindedbythenight_bats

References:

  1. URL: https://cdn.bats.org.uk/pdf/Bats_and_Lighting_-_Overview_of_evidence_and_mitigation_-_2014_UPDATE.pdf
  2. URL: https://link.springer.com/chapter/10.1007/978-3-319-25220-9_7
  3. URL: https://royalsocietypublishing.org/doi/full/10.1098/rspb.2017.0075
  4. URL: https://www.researchgate.net/publication/272889669_Impacts_of_artificial_lighting_on_bats_A_review_of_challenges_and_solutions
  5. URL: https://cdn.bats.org.uk/pdf/Resources/EUROBATSguidelines8_lightpollution.pdf?mtime=20181113114256&focal=none
  6. URL: https://ec.europa.eu/health/scientific_committees/opinions_layman/artificial-light/en/l-3/1-concerns.htm#0p0