BCT National Bat Conference 2014

September marks the beginning of the end of the bats’ active season in the UK – the maternity roosts have disbanded, the juveniles are out fending for themselves, the bats are beginning to build up their reserves to hibernate through the winter, and bat workers begin to catch up on sleep for the first time since spring! What better time to hold the Annual Bat Conference, to share the new findings and discoveries of the summer!

The conference in Warwick this year opened with a talk from the BCT’s new joint CEO’s Julia Hamner and Kit Stoner outlining some of the great work that the conference organisers have been involved within in 2014. The voice of the bat community was one of the strongest in the government’s recent Wildlife Legislation consultation with over 50% of comments relating to bats. This gave the BCT a mandate to argue the case for the continuing the protection which our bats need to ensure their conservation status. Work is progressing on the newest revision of the Bat Workers Manual and a new area of the  BCT website has been launched, dedicated to the provision of educational resources to help bat workers across the country to educate and enthuse others. Permitted development is a current concern with anecdotal evidence suggesting that bats are being missed out of the process and thus roosts are being damaged or destroyed in contravention of the legislation. BCT are calling for case studies and reports from anybody who can provide evidence or information on the validity of these concerns.

Landscape use by bats seemed to link a number of talks, with several researchers sharing the insights they have gained through radiotracking studies. This theme was kicked off with Katherine Boughey of BCT talking about the power of Geographic Information Systems (GIS) for collating over 10 years of volunteer data gathererd through the National Bat Monitoring Programme (NBMP). This can be manipulated and analysed to discover trends in the distribution of roosts and species. The BCT have produced a map of bat diversity throughout the country, showing the highest species diversity in the south west with a steady decrease as you move north and east. The data is made available to local Bat Groups in Google Earth layers and they have worked with individual Bat Groups to develop an atlas of their county, combining the NBMP data with records which the bat groups hold themselves. Katherine also outlined concerns with the current way in which data searches for protected species are conducted and explained the Core Sustenance Zone principle. Under this model, the criteria for a data record (such as a bat roost) appearing in a search would not be simply dictated by an arbitrary distance from a development but would be related to the ecology and behaviour of the species in question. The example used was to compare a great crested newt pond at 500m with a soprano pipistrelle roost at 2km – a development is much more likely to affect the more distant pipistrelle roost than the GCN pond as newts rarely travel this far from their breeding ponds. However a 1km search would exclude this roost.

A soprano pipistrelle bat in a gloved hand
A soprano pipistrelle bat in a gloved hand

The distance travelled by pipistrelle bats was elaborated on further by Madeleine Ryan from the University of Bristol. Her research involved radio tracking bats from core maternity roosts in churches, and finding their alternative roosts as well as their foraging areas and home ranges. Madeline found a variety of home range sizes for different colonies in different parts of the country, with a colony in Essex regularly flying 10km to reach a particularly large and insect-abundant reservoir after darkness fell whilst bats from other colonies travelled only 2-3km per night. Although the colonies in Cambridgeshire and Norfolk commuted shorter distances, each colony had a similar resource – such as a reservoir or other large waterbody – which seemed to be of key importance with most or all of the bats foraging there, after first starting the night feeding in darker woodlands and riparian habitat close to their roost sites.

Maggie Brown of the West Yorkshire Bat Group described their radiotracking study on noctules which were taken into care over the winter and then released with tags in the spring. The female disappeared almost immediately and was never detected again, potentially suggesting that she flew far away from the location where she was found. The second bat, a male, spent much of his time on a scarp above the river in the town, often spending time foraging over the town centre and at one point appearing to roost in a town-centre building. This gives some confidence that bats released from care do survive well and return to their natural habits, although caution must be exercised in drawing conclusions from a single bat.

Madeline Ryan’s talk also looked at the importance of church roosts to soprano pipistrelles. These bats often aggregate into large maternity colonies and can cause conflict with the wardens and worshipers of the churches they inhabit. An oft-heard argument for exclusion is that the bats can simply roost elsewhere. Whilst Madeline’s study found a number of other roosts, many of these were small roosts used by individual bats and only 10% were communal roosts of the type which are so important to successful rearing of offspring.

Matt Zeale presented the findings of studies where the behaviour of soprano pipistrelle colonies were monitored before and after exclusion from a house where the home owners had identified an issue. He found there was little change in the foraging behaviour of the bats and that new colonies often established within 3 days of the exclusion. A large number of the alternative roosts were used both before and after exclusion and the study concluded that the colonies appeared able to deal well with the exclusion. However, in many instances, the colonies re-grouped in a nearby house or building of similar construction, where they found similar conditions. This, it could be argued, is simply moving the bats from one location to another where the same issues may arise and the same action required once again – hardly a satisfactory solution.

A more positive approach was described in a talk by John Haddow about the works undertaken to limit the impacts of a large soprano pipistrelle roost on the occupants of a residential house in Scotland. The roof was cleaned and restored and a box was built to contain the bats within a particular area of the roof where there would be less impact of noise or guano. This was of limited success with the colony instead moving to another part of the building, but mitigation features such as this often take time to work and it is hoped that the bats may utilise this alternative roost in the future. In the mean time, the actions taken by the Bat Group did have the effect of reducing many of the other effects of the bats occupancy which could represent an issue to the homeowners.

Steve Roe of the Derbyshire Bat Group gave a summary of mitigation works undertaken at the Elvaston Boathouse. Works were needed to restore the boathouse which played host to a large colony of Daubenton’s bats – a species which is most commonly found foraging over waterbodies. The colony were roosting in a narrow crevice formed between two timber lintels, and an exact replacement of this feature in the new building ensured that the colony continues to use the feature 20 years on. Steve showed some excellent footage of the bats stretching before leaving their roost which you can view here.

Provision of artificial structures was one of the elements of Jane Sedgeley-Strachen’s talk on the Vincent Wildlife Trust’s Beacon for Bats project aimed at lesser horseshoe bats in mid-Wales. The project was wide ranging with much work done on the identification of the bats roosts, foraging habitat and commuting routes. This led to enhancement measures such as the improvement of roosts and foraging habitat, planting to increase landscape level connectivity and a wide range of community involvement elements to engage and enthuse a team of local volunteers. One proposals which proved more difficult than anticipated was the erection of night roosts within woodlands – this surprisingly required planning permission bur fortunately the addition of wheels seemed to provide the loophole required to install these features in the National Park woodlands. Night roosts are locations where horseshoe bats, as well as other species such as brown long-eared bats, hang up during the night to eat their prey before taking to the wing to catch more. These ‘dog kennels’ were quickly utilised by the resident bat populations and their designs have been published by the Vincent Wildlife Trust.

Two very informative talks were given on quite a contentious topic – bats and wind turbines. Oliver Behr’s talk on the Saturday was the first of these – he described research done to model the mortality risk for bats based on acoustic surveys and the weather conditions. Higher risk conditions were identified, relating to the presence of bats as well as the wind speed, the time of night and the time of year. This led to the development of bat-friendly algorithms which run the turbines, turning them off at the high risk times. This led to a six-fold reduction in the number of bats killed – a significant improvement considering the loss of revenue from electricity generated under these bat-friendly algorithms is only around 1%. Many of the commercial wind turbines across Germany are now running on these systems.

Fiona Matthews gave a summary of her research into the impacts of wind turbines on bats in the UK. This study is still unpublished but it is hoped that it will be available soon. Fiona surveyed 23% of large scale UK wind turbines using a range of techniques including acoustic surveys at height and on the ground, transect surveys and mortality searches using trained sniffer dogs to identify bat corpses below the rotor sweep of the turbines. Some of her findings appear to cast doubt on the current methods of assessment for wind turbine development; she found large variation in activity levels between different nights – indicating that a large temporal scale over at least 3 weeks may be required to fully appreciate the risk factor – and that there was little correlation between noctule and pipistrelle activity levels at height and on the ground – highlighting the need for activity surveys at the nacelle height. Fiona also highlighted concerns with our ability to assess the potential impacts of individual mortality on a population scale, considering the poor state of knowledge on bat populations and distributions in the UK, coupled with the difficulty in assessing mortality rates under suboptimal conditions where crops may prevent access or scavengers may beat you to find the corpses. This talk was interesting, concerning and incomplete as the research can not yet be published – it is critical that the findings of this studies is made available as soon as possible so that the results can inform effective design, placement and assessment of turbine projects in the future.

The Wildlife and Artificial Light symposium earlier this year highlighted the potential impacts of artificial lighting on a range of nocturnal species, with a particular emphasis on bats. Danilo Russo described an increase in cranial size of Kuhl’s pipistrelle in Italy, which corresponded perfectly with the massive increase in artificial lighting of public spaces which occurred in the 1950’s. Danilo’s hypothesis for this increase was the effect of light on tympanal moths. These moths have an ‘ear’ which allows them to hear bat echolocation and take evasive action to avoid being caught. It has been shown that light reduces this avoidance response in moths which makes them much more susceptible to bats. The pipistrelle bats therefore began to exploit this newly available resource and the larger size of the moths over their regular prey meant that a larger jaw and stronger bite gave bats with a larger cranial size a competitive advantage.

Two talks focused on the bat fauna of countries beyond our shores here in the UK. Rachael Cooper-Bohannon described work assessing the distribution of bats in southern Africa as part of the  Bats without Borders project. There are more than 120 different species but little research has been done on their ecology and distribution. The team projected the distribution of species based on their known locations – called Species Distribution Modelling – and identified the hotspots of biodiversity, as well as areas where particular families had a stronghold. The highest diversity overall was in the dry and wet savannah and afro-montane areas, whilst most species avoided the arid areas. The Rhinolophid species – the family to which our UK horseshoe bats belong – was the exception to this trend, being frequently encountered in dryer regions.

Ludmilla Aguiar dubbed Brazil the ‘Land of Bats’ – they have 15% of the world’s bat totaling over 179 species. The slideshow had many fascinating looking bat species which belong to a wide range of families with different ecologies, including insectivorous and frugivorous species as well as the infamous vampire bats. Ludmilla described some of the research being undertaken on these bats, and the threats which they are under through negative press such as the association of vampire bats with rabies. We have some fairly uninspired names for our UK species – the brown long-eared being a case in point – but my favourite Brazilian bat mentioned in the talk was Lasiurus ebenus, commonly known as the ‘blackish red bat’.

The search for new records of the most recently confirmed British species – the Alcathoe bat – was described by Philip Brown who undertook research into this subject in 2013. The Alcathoe bat is morphologically and acoustically very similar to two other small myotis bats, the whiskered and Brandt’s bats, which is the reason that it remained unknown until very recently. The initial records were from Sussex and Yorkshire with no known presence in between. Throughout the summer of 2013, a large number of bats were caught by Philip and his helpers, and more records were gathered from other bat workers throughout the UK who had captured bats whiskered/Brandt’s/Alcathoe (WAB) bats in the course of their own research. A total of 110 WAB bats were identified using DNA analysis of which 95 were whiskered, 5 were Alcathoe and 10 were Brandt’s. Sadly the Alcathoe records did not extend the currently known range of the species, although Derbyshire Bat Group announced at the conference that a recent swarming survey they had undertaken in 2014 had led to the discovery of an Alcathoe bat in Leicestershire.

The photograph of the new Alcathoe bat record identified in Leicestershire by Steve Roe of the Derbyshire Bat Group

The potential for a new monitoring scheme was the subject of a talk by John Altringham who has developed a protocol for surveying woodland bat species. The hope is that this methodology, which uses Petterson detectors and a piece of software developed by the team, can be used by volunteers up and down the country to identify the occupancy of woodland bats including rarer species such as Bechstein’s and barbastelle. Sixty woodlands would need to be surveyed three times throughout the year to allow the populations of these species to be monitored. It is hoped that the scheme could be rolled out as part of the BCT’s National Bat Monitoring Programme (NBMP) in the future.

The provision for bats within the New Land Management Scheme (NLMS) was described by James Phillips of Natural England – this is the new agri-environment scheme which will be launched in 2015. The scheme will have a ‘two tier’ approach to delivery conservation benefits for species. All UK bat species will be included within the Mosaic approach which aims to provide broad, habitat scale enhancements which would benefit a wide range of species. Some specific species which are of higher conservation concern would also be catered for through the Bespoke approach – this would involve much more targeted actions and a higher level of advice and input from Natural England on the way in which the land is managed. Species falling within this Bespoke approach would include greater horseshoe, lesser horseshoe, grey long-eared and Bechstein’s bats.

Morgan Bowers gave a very illustrative talk on the new flight cage built by the Birmingham Bat GroupBrum Bats. The drive behind this was to have somewhere to exercise and assess captive bats to establish whether they were ready to be released and to allow them to learn flight skills in a safe environment. The end result is an excellent facility which has already had over 100 bats through its doors and is proving to be a valuable resource for trainee bat carers as they can learn to handle bats in a safe environment. You can watch footage of pipistrelle bats using the flight cage on Brumbats’ Youtube channel.

Two awards were given at the conference. The Vincent Weir award was presented to Anna Berthinussen for her work on the impacts of roads on bats, and the effectiveness of current mitigation measures such as underpasses, bridges and gantries. The Pete Guest award was awarded to Colin Morris of the Vincent Wildlife Trust for all of the positive work he has done for bat conservation. His talk focussed the mammoth undertakings of the local Bat Group in extending and enhancing the roosting opportunities for horseshoe bats in an important site in Dorset.

My personal highlight of the conference was the workshop talk given by Laura Grant on migration in UK bats. Many European species migrate, including species which are found in the UK such as noctule and Nathusius pipistrelle. Around 3% of bat species globally are known to migrate and this has developed in separate genetic lineages to allow the bats to make annual movements to where conditions or resources are optimal – for example to hibernate in suitable conditions or to exploit a seasonal abundance in food supply. Laura described a suite of studies and methodologies used to assess the migration of Nathusius pipistrelles between the UK and Europe – these included banding surveys where individual bats are ringed, stable isotope analysis to work out the broad geographic region where a bat was resident at its previous moult, and acoustic surveys such as those undertaken by BSG which looked at the comparative frequencies of different bat species at the predicted key migration points. These latter studies found that Nathusius pipistrelle had a different pattern of peak activity to other UK species recorded at the locations, with a focus around spring and especially autumn when it is predicted that the species would arrive at or leave our shores. More on Nathusius pipistrelles can be found here and a video of the Nathusius pipistrelle project in London is available here.

Once again, the BCT succeeded in putting on an inspiring and educational programme with talks ranging from mitigating individual roosts to broad scale impacts to populations, education on the bat fauna of other countries and current research which tells us more about the behaviour of our familiar UK species. The only downside with the conference is that it peaks your enthusiasm just as the bats’ active season is drawing to a close, but the bat groups rarely let this slow them down and they undertake hibernation checks at a range of roosting sites throughout the winter months – find your local group and get involved with these fascinating creatures. For more information on next year’s conference and on other events run by the BTC, check out their events page.


BCT Artificial Light and Wildlife Symposium 2014

The Artificial Lighting and Wildlife conference was held in London on the 20th and 21st of March 2014. It’s scope included effects on a range of wildlife but, being sponsored by BCT, bats were a key focus. Full details of the symposium can be found here. This is a short piece I wrote up for the local bat group but I’ve added in the references and a couple of illustrative photographs below!

Artificial lighting is ubiquitous and almost universally accepted – we have street lights for crime prevention and traffic safety; architectural lighting of statues and churches; lighting of industrial sites to allow work to continue 24/7; and light spill from inside houses. Three scary facts which illustrate this are:

#1 Artificial lighting increases globally at a rate of 6% per year;
#2 There are 7.4m street lights in the UK and;
#3 20% of UK energy expenditure goes on lighting.

Variations on this photograph - a satellite image of the earth at night showing the extent of artificial lighting - was the most widely used photograph throughout various talks and rightly so - it serves to show just what an impact we have on the natural environment.
Variations on this photograph – a satellite image of the earth at night showing the extent of artificial lighting – were the most widely used photograph throughout various talks and rightly so – it serves to show just what an impact we have on the natural environment. Photo copyright: NASA

Most bat workers will know of research, such as Emma Stone‘s work in Bristol, which shows that slower flying species such as horseshoe, long-eared and myotis bats tend to avoid light and that lighting their commuting routes can cause severance. Much of the interesting new research at the symposium came from Holland; Herman Limpens looked at whether there are more ‘bat friendly’ lighting spectra and found that amber light caused much less avoidance than white or green light on bats commuting along a dark canal corridor. This was also borne out in analysis of Irish monitoring surveys which found much lower levels of Daubenton’s activity at lit waterway locations. Fiona Matthews from Exeter University put paired static detectors in light and dark locations in a 2km radius around greater horseshoe roosts and found much higher activity levels were recorded in the dark.

Bats can be disturbed when roost entrances are lit: the Life at Night project changed the lighting regimes of churches in Slovenia and achieved significant improvements in both emergence time – horseshoe bats left earlier – and consistency – bats left over a much shorter time period. Kamiel Spoelstra from the Netherlands Institute of Ecology found pipistrelle occupancy rates of boxes to be significantly reduced under white and red light treatments compared with dark.

The ubiquitous Illuminated Church – the subject of the Life at Night talk (photograph from the Life at Night Project Website http://www.lifeatnight.si/en/)

But the picture is not that simple; some species such as pipistrelles and Leisler’s are actually attracted to streetlight. Their speed makes them less susceptible to predators and anybody who has undertaken moth trapping will know that moths gather at light sources, especially attracted to shorter wavelength and UV light. A fascinating talk by Andrew Wakefield from the University of Bristol added a further dimension to this – he found that the avoidance behaviour usually exhibited by moths in response to a bat echolocation call – a change of course or a power-dive where they drop to the ground – is reduced by 60% under lit conditions making them a much easier prey for bats.

The impact of lighting upon invertebrates was widely discussed; for example it was found that larger moths with larger eyes are most attracted to shorter wavelength light and they are drawn in at 6x levels compared with longer wavelength light. This attraction is well known but the implications are rarely considered; Matt Shardlow of Buglife estimated that a third of interactions between moths and light sources would prove fatal to the insects through exhaustion, collision, heat or predation.

The influence which lighting can have upon the relationships between species was a trend which came out in a number of the talks – the impact then can be considered positive or negative, depending upon your perspective. Parasitoid rates on moth eggs were much higher under lit conditions as the diurnal parasitoid gains the advantage. Redshank increase their foraging in lit areas, favouring the redshank (perhaps?). Similarly, a Leisler’s bat can forage more efficiently, but to the detriment of the moths which are preyed upon. Lighting at night disturbs and disrupts the natural rhythms, dynamics and ecological signals.

A peacock butterfly seeking out a dark place to hibernate.
A peacock butterfly seeking out a dark place to hibernate.

One of the last talks of the symposium was from Kate Harrington who found evidence for in-combination effects of artificial light and artificial noise on bats – as the two are so often associated such as from traffic along well-lit roads, the potential for this to modify the natural environment more severely is significant.

Several talks discussed the importance of good design in lighting schemes for new developments – light only where it is required, light as low as required and design cut-offs and cowls to avoid unwanted light-spill onto surrounding habitats. The project along the Thames at Richmond is an excellent example of this – this video shows how the lights respond to pedestrians so that they feel they are walking in a pool of lights whilst all around remains dark. The importance of maintaining dark corridors was also an important part of the London 2012 park design.

The copper beech outside the Guildhall on the High Street in Grantham showing the extent to which lighting is a normal and accepted component of our villages, towns and cities.
The copper beech outside the Guildhall on the High Street in Grantham showing the extent to which lighting is a normal and accepted component of our villages, towns and cities.

But new designs are only going to reduce future problems – as I walked back from Grantham station after the conference I was shocked to see the level of light-spill onto hedges, trees, the River Witham and other suitable foraging and commuting habitat. I had never appreciated how much of an effect our lighting of the environment would have upon the species we share it with. BCT will be putting up the videos of the talks and presentations in due course so keep an eye out for the news of their arrival!

BCT Bat Conference 2013

This year’s National Bat Conference, organised and run by BCT, was at Warwick University last weekend. The conference is always held in September and I always come away with a mixture of enthusiasm and regret – it’s a great opportunity to chat to other bat workers, both volunteers and consultants, and listen to some fascinating talks which really inspire you… but it is held just as the main bat season is drawing to an end and there is little time left to go out and carry out the surveys which the conference inspires! I have certainly come away with a few ideas for next spring.

Serotine bat in the hand

Several of the talks this year could be grouped broadly into the ‘state of bats’ category. This included the opening talk by Julia Hanmer, the chief executive of BCT, who outlined the work which BCT have undertaken in the last year with a special focus on the work being done to help churches with bats find solutions which allow both to coexist. Lincolnshire Bat Group’s own work in Tattershall Church was held up as a particular example of how the bats could live happily alongside the congregation with input and guidance from experts and this topic was taken up and explored in more detail later in the programme by Laura Bambini who has been been working alongside church wardens and congregations to find out the ways in which bats do genuinely impact upon the running of a church, and what information and support can be provided to alleviate these concerns. This positive work was set sadly against a backdrop of the general anti-environmental ethos of the current government, with Owen Patterson’s name being rightly greeted with boo’s and hisses by a conservation-minded conference congregation. The fact that the Chief Constable who leads on Wildlife Crime is openly anti-bats was another shocking revelation and goes to show just how much prejudice we need to work against.

Pete Charleston heads up the BCT investigations unit and took the stand for the next talk. BCT and Pete in particular are doing great work to combat wildlife crime relating to bats, with regular increases in numbers of referrals and numbers of prosecutions. We are sadly let down at present however by the prosecutors themselves; a recent case where a developer knowingly destroyed six bat roosts and was fined just £35 per offence is grossly disproportionate to the crime committed and serves to send out entirely the wrong message to those who view the protection of our native wildlife as an impediment to their own economic gains – a mantra perpetuated by George Osborne in his recent attacks on protected species legislation.

Leaving politics aside, and on a much more positive note, Lisa Worledge and Helen Miller gave a talk later in the morning on the current research on Pseudogymnoascus destructans in Britain and Europe. This is the fungus responsible for the deaths of huge numbers of bats in hibernation roosts in the USA and there is a fear that the pathogen could cause similar destruction to our native species. The talk concluded that there was cause for cautious optimism that the bats in the UK had in fact co-evolved alongside this fungus and were therefore relatively unaffected by it. The basis for this is the identification of the fungus in environmental samples from across Europe and in the majority of hibernation sites surveyed in the south of England in a recent pilot study, as well as the positive identification of the fungus on a hibernating bat for the first time in the UK, yet without seeing the same devastating effects which are associated with the fungus in the US. The genetic diversity observed in the fungus across Europe suggests that the pathogen has been present and has developed into differing genetic strains across its range, whilst the homogeneity of the fungus genome in the USA suggests a much more recent introduction. The fact that this fungus appears to be novel in the USA would explain why the bats there are being so badly affected in the same way as a new flu strain can strike down half the country. The risk of the disease blighting our UK populations has been cause for concern for a number of years now, and cautious optimism is certainly a better outlook!

The importance of bats within an ecosystem, and the risk of losing such an important species, were highlighted in a talk by Ryszard Oleksy who has been undertaking work on the role of the Madagascar flying fox on forest regeneration in Madagascar. This is a large fruit-eating species, very different to our tiny insectivorous UK species, but the importance of the genera on an ecosystem scale is likely to be similar. The study found that 110 plant species are included within the diet, that seeds which have passed through the digestive system germinate well and that the distance which an individual bat can disperse seeds is significant. The species makes a very effective agent of forest regeneration, linking up isolated forest patches in a fragmented landscape and assisting in the dispersal of a number of endemic plant species.

One issue which is well known to most bat workers now is the risk which breathable roofing membranes (BRM’s) pose to bats roosting within buildings. Bats can easily become entangled in many of these membranes and there are reports of over 100 bats being killed by becoming trapped and dying of dehydration or exhaustion, and yet they are put into new roofs on an almost routine basis, including roofs where known roosts may be present. Stacey Waring gave an excellent talk on her research into this issue, combining a more abstract lab-based tests of the extent to which different membranes on the market become ‘fluffy’ and as such, of risk to bats; with tests of how the membranes performed with captive bats within a rescue centre. All of the membranes tested were found to pose a risk, compared with traditional bitchumen felt, although there is hope that the findings of this study may feed into the design process and more bat-friendly materials may become available in the future.

Geoff Billingham gave a talk on Wolvercote Tunnel in Oxford, outlining the results of a range of surveys and a concept of mitigation designed to ‘flush out’ bats from the tunnel in advance of an oncoming train to avoid them being killed. This relied upon lights being turned on in the centre of the tunnel a few moments before the arrival of a train, and then progressing out to the peripheries with the hope that bats would move ahead of the advancing light. The most concerning figure within this talk, to my mind, is the 5 dead or grounded bats identified in 21 visits to the tunnels. Trail cameras also identified an average of three visits per night from species such as foxes or cats, which would scavenge a bat carcass, making it unlikely that a dead bat would remain for a long time. This rate of killing is significant, considering that the tunnel is 130m long, the trains run at 30mph and they do not run much beyond 10:30pm. If this number of bats are killed in a single tunnel, the number which must perish across the country is highly significant and is likely to have a serious impact upon populations. It also puts into perspective the potential impact of new technologies such as wind turbines, when viewed in comparison with more established and accepted threats which may be of much greater significance.

Four talks over the weekend discussed the ways in which we can increase our knowledge of the distribution of bats within the UK.

Two focussed on islands – the first of these was studying the distribution of rare woodland bats, specifically Bechstein’s and barbastelle – on the Isle of Wight. Ian Davidson-Watts sampled in 42 different woodlands across the island and used mist nests and harp traps to catch bats and radio-tag them. Two thirds of the woodlands were found to have Bechstein’s present – this is one of the Myotis species and one of the rarest species in the UK – and a number of maternity roosts were subsequently identified. The surveys also identified potentially the largest barbastelle roost within the UK with over 115 individuals counted out. These findings make the Isle of Wight of potentially international significance for rare woodland bats at a landscape level.

Moving to the opposite end of England, Hugh Watson discussed static detector surveys on three islands off the Northumberland Coast to identify the species present. This is an under-recorded area and a total of five species were recorded on the islands with evidence of bats commuting to forage from the mainland.

Two further talks discussed mass-participation bat surveys where a large number of the general public were encouraged to get involved, to learn more about bats and to extend the coverage of bat records within a county.

The Norfolk Bat Survey set up a number of ‘Bat Monitoring Centres’ across the county so that everybody was within 15-20 miles of a station. The public could sign up for the survey and then pick up a static detector which would be put out at a number of locations within a 1km square and left to record the bats which went past. This has enabled bat records to be obtained for a large area of the county, and allowed interested individuals to find out which species fly through their gardens and their local landscape when darkness falls.

The Somerset Bat Group by contrast have designed their Big Bat Survey – a number of transects across landscapes within the county, including the Blackdown Hills and the Mendips, where a group of at least four people would be equipped with bat detectors and would walk the set routes to find out which species were present. Fifty and seventy members of the public took part in the respective surveys, and the results were again invaluable in increasing the knowledge of both the distribution of species within each area and their use of the various habitats present.

The last two talks focussed on technological advances in our approach to bat surveys. The first of these was a talk by John Atanbori of Lincoln University who is using computer vision techniques to automatically pick out bats from a video taken in low light levels and compute metrics such as wing beat frequency, with an aim to using this as a tool for species identification. The characteristics of bats in flight differ between species to a greater or lesser extent, as anybody who has watched the rapid wing-beats of a foraging pipistrelle alongside the broad-winged fluttering of a brown long-eared will know. The project is a work-in-progress but offers a fascinating new avenue of species identification if it can be developed.

The final talk was given by Ian Agranat of Wildlife Acoustics on their latest classifiers for UK bat calls. The aim of this software is to identify a bat call to species level (or genus level in the case of the myotis bats) without a bat worker needing to scan through every single call. The need for this technology is increasing as the price, availability and usefulness of static bat detectors is growing – these provide very cost effective monitoring of a site compared with human surveyors, but they do produce huge amounts of data which needs to be sifted through. The Wildlife Acoustics technology uses machine learning where a large number of identified calls are fed into the software and the algorithms identify differences which split the sound files up by their respective species. This is successful at an 80% accuracy which would significantly speed the process of analysis, whilst still at this stage requiring a certain level of operator confirmation and amendment. It is another exciting avenue of development and another ‘watch this space’.

Workshops were wide-ranging as usual and it is always a shame that you can only pick one or two. I opted for the tree roost field survey workshop with Henry Andrews taught me a number of new things as well as re-enforcing many others with examples and photographs which were invaluable, even after a summer spent up trees and inspecting potential roost sites. In case you haven’t come across his Bat Tree Habitat Key – you can view it for free on his webpage. The key to extending and refining this already invaluable piece of work is to gather more records – calling anybody working on bats and trees to contribute! On the Sunday I opted for Jon Whitehurst’s talk on an Introduction to Species Distribution Modelling – a last minute switch but one which has me itching to try out the techniques he outlined to model bats’ use of the landscape.

As I said at the outset, the only downside to the conference to my mind is that it is at the end of the season and so all of these great ideas and enthusiasm to get out there have to lie dormant through the winter until the spring when the bats come out of hibernation and the survey work can begin again.
Next year’s conference is due to be held at Warwick University again and you can find out more on the BCT’s website here and the BCT blog on the conference proceedings is to be found here. There are photographs from the conference on the BCT’s facebook page here, including the customary after-dinner Ceilidh!

BCT National Bat Conference 2012

The Bat Conservation Trust (BCT) run a national bat conference annually – this year’s event was over the last weekend up at the University of York. The event is based around a series of talks, workshops on particular topics and stands run by various manufacturers of bat-related merchandise from books to detectors to jewellery. But the whole thing really hangs (pun out of the way nice and early) on the conference dinner and ceilidg on the Saturday night!

The conference crowd covers the full spectrum from enthusiasts to professionals although in my experience, most people fit somewhere towards the centre with a bias one way or another – the industry of protected species surveys means that the impressive knowledge and experience of bat group members is in high demand even if only on a casual basis. The age range of the attendees is also similarly diverse, from younger graduates to older veterans and again, this is an excellent opportunity for everybody to learn something new.

Serotine bat in the hand
Serotine bat in the hand

The opening talk was from BCT chief executive, Julia Hanmer. This provided an overview of the work that the trust has been carrying out over the last year, the initiatives started and the priorities identified. The bad press for protected species in general this year, courtesy of George Osborne, was of clear concern. His rhetoric on the issue was fairly ill-founded, as a government review (the Habitats Directive Review) subsequently found, but the headlines do not help the cause. Other areas progressed include the new guidance issued earlier this year – a revision of the Bat Surveys: Good Practise Guidelines – and the shift in the BCT’s training programme to meet this, alongside an emphasis on greater knowledge-sharing via the mitigation case studies website.

This should certainly be a priority – there is so much work carried out on bats and bat roosts within the UK which is simply not shared outside of the company which carries it out. There must be a vast wealth of knowledge which is untapped and patterns of success or failure which are not being identified. This is understandable within consultancy, with issues of data ownership and client confidentiality always causing concern. One of the most valuable opportunities which the conference offers is to share this knowledge informally with other delegates and gain new ideas or insights which might help to improve mitigation and survey effort. I wonder whether Natural England might be able to assist in this area however; consultants are unlikely to post a case study of how they got something wrong but this can be as (if not more) useful that knowing how they got it right. Natural England on the other hand receive all mitigation proposals which go to licence, and should receive monitoring data on the success of these schemes. If they were able to analyse this vast wealth of information – it would make a fascinating PhD topic if they didn’t have the resources themselves – a huge amount could be learnt and this could provide a much stronger evidence base for consultants to design mitigation.

Linking in very nicely with this topic was a talk by John Altringham on the effect of road disturbance on bat activity and diversity and the effectiveness of current mitigation practice. This touches on both the ‘bad headlines’ often attributed to bats and the issues with mitigation schemes. Bats ‘commute’ along linear features such as woodland edges, hedgerows and rivers to travel between roosting habitat and foraging habitat. These linear features can very easily be severed if a new road is built or an existing road widened to include more carriageways. Species differ in their behaviour in this case – Emma Stone (whose talk appeared later in the schedule) found that even lighting a 10m section of hedgerow would prevent lesser horseshoe bats from using one of their regular routes so imagine how much greater a severance a fully lit tarmacked duel carriageway would present. James Hale (whose presented his study on the Sunday) looked at the behaviour of common pipistrelle bats in Birmingham city centre and found that, although they prioritised shorter breaks in their commuting route, or the darker areas of these gaps, they would use commuting routes which were split by busy roads. These two species are probably towards the extreme ends of the behaviours displayed by bats but each represents a significant concern if a new road is built; lesser horseshoe bats will be separated from habitat on the other side of the road whereas pipistrelles may well continue to cross as they always have, with unmeasured levels of mortality caused by subsequent car-strikes.

The standard mitigation has been to either push bats up over the road – using green bridges, bat gantries, bat wires or similar – or to encourage them below the road through underpasses. These methodologies have been used in the past on several schemes but their effectiveness has not been monitored. Where monitoring has taken place, John Altringham identifies a confusion between ‘use’ and ‘effectiveness’ – if a bat were observed to use a bat wire, it was concluded that the bat wire was used and that the mitigation was therefore effective. However one bat is a fraction of the population – if one bat crosses safely and twenty cross unsafely, this is not effective mitigation. The conclusion reached was that bat wires and gantries – those which draw negative headlines due to their cost – are not effective mitigation. Underpasses were found to be more effective, although there was variation in their utilisation – 94% of bats made use of one which was studied by Altringham whereas another only attracted 30%. There were differences in the height of the underpasses, the position in relation to the original commuting route and other variables which might impact upon this success rate but the key problem is that we simply do not know. I understand that a PhD is about to begin looking at this very issue and I very much look forward to hearing the results and conclusions in a future conference – this kind of scientific approach, with appropriate controls and comparisons is exactly the kind of information which is needed if the work carried out to protect bats and safeguard populations is to be effective.

Charlotte Walters gave a talk later about a new tool – iBatsID – which will take a recorded echolocation call and provide a probabilistic identification of the bat species. The tool was developed using a machine learning algorithm – an Artificial Neural Network – which was fed with a vast number of bat calls from a range of species. The ANN then identified characteristics of the acoustic pulses which could be used to distinguish between different species, and can then work out the most likely identity of any particular call it is subsequently presented with. Bats show a wide range in their echolocation calls – this includes variation in call length (how long the pulse lasts for), the frequency of the call, the distribution of frequencies between constant frequency (cf), frequency modulated (fm) and the range of frequencies which each of these covers, the shape of the call and others – a total of 24 characteristics in all. See image below for a couple of example calls from different UK species – you can see how different they are. The paper presenting the tool can be found here.

Bat calls composite display
A few examples to illustrate how bat calls can vary – each distinct call is a single echolocation pulse. The noctule has long, low, CF calls, the myotis has straight, mid-range frequence FM calls and the pipistrelle has an FM sweep with a CF tail. I have put these calls together manually (they weren’t all flying together) but the platform for the analysis is the BatSound application. Each call is a single echolocation pulse, bats emit a series of these at a frequency anywhere from around 5 per second for a slower noctule pass and 20 per second for a faster myotis pass.

This talk, and the questions which followed, provided a glimpse of the slight discord between the extreme ends of the spectrum of attendees. One member of a bat group was disappointed by this approach to bat analysis, feeling that it took away from the skills and experience of a bat surveyor and allowed one machine to feed information to another machine which would then provide the answer that such a surveyor may not be able to interpret. There is validity to this argument if, as he feared, the surveyor would be otherwise untrained or inexperienced but drawing their information from this computerised output alone. However because of the way that larger scale surveys are frequently carried out these days – as a workshop on battling with data by Atmos Ecology staff identified, static detectors could easily record close to a million calls for a single wind turbine study site – the advantages of some level of automated analysis are immense. Tools such as this should, as Walters correctly pointed out, be seen as an useful additional tool for bat workers but are not intended to replace the knowledge and experience which really are critical to good analysis of findings and the ability to propose mitigation and compensation based upon it.

Graeme Smart, from the Northumberland bat group gave a very engaging talk on the Nathusius pipistrelle in Northumberland. This is one of the more rarely encountered species in the UK and there are questions as to whether the Northumberland population are resident or migratory – they are known to be present in every month between May – October but their disappearance in the winter months could be due to hibernation or migration. The migration theory was supported by a sighting of a Nathusius pipistrelle making landfall by a birdwatcher on the beach; the bat was found to be underweight and dehydrated which would support a long flight across the sea. This individual was taken in by the bat group, fed and rehydrated and successfully released shortly afterwards. The bat group are using a range of methods to try to establish whether the population is present over the winter, but the most innovative and exciting is perhaps the attachment of a bat detector to a cross-channel ferry which monitors for bats during the ship’s nocturnal passes. As Smart said, it is a little like looking for a needle in a haystack but that doesn’t mean that it would not be worth looking and it would be fantastic if a bat were picked up via this method. The BCT run a Nathusius pipistrelle survey which aims to extend our knowledge of where this species is found in the country. Nathusius pip’s are very much associated with waterbodies and the majority of roost sites are very close to larger areas of water – if you sign up, BCT will allocate you a lake to visit twice in September to look for this species. I have been undertaking these surveys at a nearby reservoir but with no luck so far!

A later talk by Caroline Moussy from the University of Exeter was tackling a similar question in a different species using very different methods. The serotine bat is largely restricted to the south of England, with a few exceptions which rise up the east and west of the country, but is widespread on the continent. Moussy used genetic techniques to look at what gene flow could tell us about mixing between populations both within the UK (as they fall into three distinct regions) and the European populations. The results found evidence of movement between populations on the continent and the UK residents but very little visa versa. Movement between the Isle of Wight to the western population and the eastern population to the western was also found but very little from the west to the east. Although the techniques used are advanced and require specialist equipment, this approach gives a very definitive answer the questions of movement posed and could, in principle, assist in the question of the Nathusius pipistrelle migration in the previous talk.

One very useful tool for protecting bats is to know where they are and the talk by Richard Dodd on the bats and bikes project showcased a novel way to extend our knowledge of their distribution. This was a partnership between the Nation Cycle Network Sustrans and the local Cardiff and Valley’s bat group. The methodology is fairly straightforward, an AnaBat detector was placed in a backpack with a microphone mounted on the top of the helmet and volunteers cycled 1-hour stretches of the Taff Trail between Merthyr Tydfil and Cardiff and analysed the results upon their return. With a GPS unit attached to the AnaBat, each of these calls was geo-referenced so they could see exactly where each call was picked up. Driven transects have been used for a while now but this seems to be a novel approach to gathering data over a wide area which is not accessible to cars. A total of 401 calls from six species were recorded with some clear habitat associations observed, for example the Nathusius pipistrelle was recorded at points where the route ran alongside a river. I would expect that this methodology could be taken up by more bat groups in the future and I do hope to have a go in an area of local woodland soon as a good way of getting a snapshot of activity throughout the habitat in a relatively short period of time.

Stephanie Murphy presented a talk about patterns of habitat use in brown long-eared bats which tied in rather nicely with the final talk by Toby Thorne on the spatial analysis of roosting associations of BLE’s and Natterer’s bats in broadleaf woodland. Using radio-tracking of 38 brown long-eared bats, Murphy found that primary and secondary foraging areas could be identified within woodlands. Core areas, those which were preferred, frequently had a higher percentage under-storey cover and species richness that the peripheral habitats. There was overlap in the core areas used by different bats which suggests that the distribution of foraging within the woodland may be related simply to habitat quality rather than a more territorial dividing up of resources. Thorne found that, within Finemere Wood, four groupings of brown long-eared bats could be identified, although there was some mixing between groups. This suggests that a given woodland may have a number effective populations and therefore any impacts such as management should not be considered to affect ‘the brown long-eared population’ but perhaps one group more than others. A lower level of non-random association was found between Natterer’s bats which seemed to form less strong associations.

Hibernating brown long-eared bat in a bat box
Hibernating brown long-eared bat in a bat box

Murphy found that brown long-eared bats switched maternity roosts with some regularity – 21 out of 28 used only one roost whilst others changed up to nine times throughout the season. It would be interesting to see what these figures would show for Natterer’s bats, to see whether perhaps a greater tendency to switch roosts, as found by Smith and Racey in their 2005 paper: The Itinerant Natterer, might influence the pattern observed by Thorne.

Other interesting results presented by Murphy related to the roost sites used by BLE’s; 60% were in buildings whilst 40% were in trees, 27 of the roosts were in oak with one in ash, 63% of trees were greater than 50m from the woodland edge and roost trees tended to be the largest in the quadrat. All of these would be useful characteristics to use when assessing trees for potential roost sites.

I think that the highlight of the conference for me was a workshop on surveying trees for bats, run by Henry Andrews. This talk was fascinating, engaging and eye-opening. Andrews has carried out extensive research, looking outside of the standard sources, and changed the way he approached surveying trees as a result. Brown long-eared bats frequently roost within buildings and received wisdom will tell you that the ridge beam is where they are most often identified. Following this information, Andrews looked at the type of wound/fracture/feature within trees which was most likely to provide similar conditions in trees and came up with the stress fracture – an often horizontal split in a branch which creates an upwardly extending cavity with dry conditions which is very similar to the ridge board of a house. His first targeted inspection of one of these features turned up a roost.

He provided the workshop group with a range of ‘roosts’ – actual logs and pieces of timber cut away to reveal the internal structure so that from a woodpecker hole, the trunk was opened out to show the nest cavity within. Similarly were examples of frost and snow damage, rot holes and the stress fractures, as well as the features which can be made when a tree splits to multiple leaders and a cavity forms at the join. Alongside these examples was information on what evidence to look for, where to look for it, when and how to carry out the surveys and a brief guide to the best kit for the job.

Andrews has gathered together information from many bat workers on the nature, location and features of tree roosts and has produced a guide called the Habitat Key for the Assessment of Potential Bat Roost Features in Trees which can be downloaded from his website. This is an excellent document which really typifies the type of information which needs to be brought together, collating experiences to allow broad trends to be identified as well as the more exceptional situations which show just how dangerous it can be to rule things out. Received wisdom is not always correct! He has promised an update towards the end of the year and I very much look forward to this becoming available.

My own contribution to the knowledge of bats in the UK is as follows: Judging from the relative abundance of different species as ‘incidentals’ within slideshows throughout the conference, it can be concluded that the most appealing/photogenic species is… the brown long-eared by a small landslide!

Here’s looking forward to next year’s conference, details will become available on the BCT webpage sometime next year which should be found here!
If you are interested in getting involved in bat surveys or to find out more about these fascinating creatures, try contacting the local bat group, both the Lincolnshire Bat Group and the Leicestershire and Rutland Bat Group are very friendly, welcoming and knowledgable. They will also be able to help if you have any bat-related queries or if you find a grounded or injured bat. If you want to support the fantastic work of the BCT and help conserve British bats, think about joining them here! Their website also has lots more information about British bats including individual species fact sheets here.

Lesser horseshoe bat
Lesser horseshoe bat