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BCT Bats and Woodland Symposium

Grantham Ecology2 Comments

The BCT Bats and Woodlands symposium was organised in conjunction with the Warwickshire Barbastelle Project and was held in Rugby, Warwickshire on 18th November 2014. The outline below is a brief summary of the talks and topics covered:

woodland in spring

Bats and Woodland Overview (Helen Miller, BCT)

The first talk was from Helen Miller – BCT’s Woodland Officer. A wide range of bats utilise woodland habitats for activities including roosting, foraging and commuting. National Biodiversity Network (NBN) data shows that there is a positive association between bats and the extent and proximity of broadleaf woodland whilst other analysis show that roosts of 5-6 of our bat species are significantly closer to woodland than would be expected by chance. The peripheries of woodlands are frequently used by edge specialists such as pipistrelle species, noctule and Daubenton’s bats, whilst the interior is favoured by other specialists such as the brown long-eared, Natterer’s and Bechstein’s bats. The importance of woodlands to bats are reflected by the number of documents which are available to offer guidance on the management of woodlands for the benefit of bats including the Woodland Management for Bats, Development of Good Practice Guidelines for Woodland Management for Bats, and the UK Forestry Standard.

A history of British Woodlands (Oliver Rackham)

The next talk was by Oliver Rackham whose books on the history of the British countryside – especially woodlands and wood pasture – represent the authoritative texts on the subject. The fabled ‘wildwood’ land cover of the UK historically is likely to have been a complex and dynamic grassland/woodland mosaic which cycled on a roughly 1000 year basis. Factors such as drainage, fertility and the actions of herbivors would have prevented the comprehensive woodland cover which most people imagine. This habitat is still found in wood pasture and parkland habitats where the trees and grassland co-exist and these habitats are where the ancient, gnarled trees are most often found. Closed woodland is not conducive to the development of ancient trees as they are out-competed over time whereas they can survive as standards in parkland, and the grassland/woodland mosaic of the wildwood is likely to have naturally created these trees. The management of ancient woodlands has, for hundreds of years, been for the benefit of the locals and foresters. This meant that trees were coppiced and pollarded to allow them to be sustainably harvested – the development of large trees would be outside of the ability of the foresters to deal with, before the advent of power tools. Oliver Rackham suggested that this may mean that woodlands of the past may have been less useful to bats as these larger ancient trees were not present.

Henry Andrews, who has done much work recording and collating records of tree roosts, pointed out that this assumption that bats are associated with ancient trees is often false as roosts frequently occur in many much younger and smaller trees which are more likely to have been a component of these managed ancient woodlands. Henry Andrews’ Bat Tree Habitat Key page on facebook has many videos of the much younger trees which develop roosting features. Oliver Rackham suggested nonetheless that perhaps ‘bats have never had it so good’ in terms of roost availability with extensive roosting opportunities associated with more larger trees in less managed woodlands. There do, from personal experience, seem to be many features apparently suitable for roosting bats in woodlands where I have climbed and inspected. This would suggest that it is perhaps the loss of foraging habitat, the mechanisation and intensification of agriculture and the impact of these on the insect food source of bats which is responsible for their huge decline across the 20th century.

Branching out: understanding the importance of woodland to the barbastelle (Matt Zeale, University of Bristol)

Ian Davidson-Watts gave two talks back-to-back, first covering Matt Zeale’s talk on the importance of woodland to barbastelle bats before moving on to his own topic. Barbastelles are a rare species in the UK – sparsely but widely distributed. They are mainly tree roosting and specialise in foraging on hearing moths – that is those which are able to hear bat echolocation and take evasive action. This ability has developed in an evolutionary arms race with the result that barbastelle echolocation is 10-100x quieter than similar species. They are a stealth predator and they may therefore be under-recorded by acoustic survey methodologies. The barbastelle bats radiotracked in the study spent the first 1-2h in their roost woodland but would often forage 6-7km from their roost throughout the night with some individuals travelling 12-17km. Many of the barbastelles studied are highly associated with foraging habitats over water, although studies in 2014 on a Lincolnshire colony found that these individuals did not appear to exhibit this habitat selection. The bats roosted most frequently under loose bark with 80% of their roosts being found in these features although splits were also used. The nature of these roosts is transient as they are often in dead or dying trees – only 22 of the 36 roosts found during one year were still standing and suitable the following year indicating a high turnover of roosts. For this reason it was argued that the woodland, rather than the individual trees, should be considered as the roost.

Life on the edge – the importance of woodland to pipistrelles and other ariel hawking bats (Ian Davidson-Watts)

Pipistrelle bats are often thought of as ‘edge’ or ‘generalist’ species reflecting their use of this semi-cluttered environment such as woodland edges, gardens and hedgerows as opposed to a dense woodland or open grassland. Ian argued that this is too simplistic – 43% of bats captured in woodland interior in trapping surveys were common or soprano pipistrelles and a bat logger found that 50% of calls within the woodland belonged to these two species showing that they do forage within the interior of woodland and are one of the most common species encountered there. Pipistrelles are often seen foraging around the canopy of woodlands even before sunset and Ian suggests that up at this level, there is a lot of ‘edge’ between tree canopies and the air, if we consider the woodland in a 3D manner rather than from our own perspective on the ground. Common pipistrelles showed a selection for deciduous woodland whilst soprano pipistrelles show a significant selection for riparian woodland habitat.

What appears a cluttered woodland interior from the ground could be much more open and 'edge' in character in the canopy - we must consider habitats from a bat's viewpoint rather than our own.
What appears a cluttered woodland interior from the ground could be much more open and ‘edge’ in character in the canopy – we must consider habitats from a bat’s viewpoint rather than our own.

Brown long-eared bat woodland ecology (Stephanie Murphy)

This study radiotracked 38 brown long-eared bats in 18 different woodland sites and monitored their movements over 3-6 days. The researchers identified a core foraging area for each individual which was an average of 2ha along with further peripheral foraging habitat where the chance of encountering the bat was around 50%. There was an increase in range size as the active season advanced as well as an increased use of hedgerows for foraging in July and August (although the latter did not account for the former). The key difference between the core and peripheral foraging area seemed to be a more diverse understorey – hawthorn, alder and hazel were more prevalent in the core areas. Bats which were caught together were often found to overlap their foraging areas but did not interact. They were however more likely to be found roosting together.

All female bats monitored roosted in, or adjacent to, the woodlands in which they were captured. 46 roosts were identified – 14 of these were in buildings whilst the remainder were in trees. All of the tree roosts were in oaks with the exception of one ash. The trees tended to be amongst the largest trees within the 50 x 50m quadrant they are in, and 21% of the roosting features used were not visible from the ground. The majority of tree roosts were more than 50m from the woodland edge. Around 50% of the bats used only a single roost during the trapping period whilst 25% switched once and the remaining 25% switched 2-7 times. Colony sizes were larger in building roosts than in trees and switching of roosts was more likely in trees than in buildings.

16 years of ringing Bechstein’s bats – what it has told us (Colin Morris)

The Bechstein’s bat is one of the rarest in the UK – it is a large myotis species with distinctive large ears which is a woodland specialist. Ten bats were radiotracked over two summers and were found to use foraging habitat ranges of 7-50ha at a maximum distance of 300-900m from their roost. There was a strong preference for closed canopy with understory – water and pasture foraging areas were the second and third most favoured habitats. 

The Bechstein’s bats in the Brackett’s Coppice in Dorset make use of Schwegler bat boxes erected by the Vincent Wildlife Trust. Both the large 1FW and the smaller 2FN boxes are used by the bats – the large 1FW boxes are used as maternity roosts with a strong preference shown for these in June and a strong preference for the smaller 2FN boxes in May and September before and after the maternity season during the ‘transitional periods’. The bats using the boxes are monitored and ringed and this has allowed their population dynamics to be observed over a long time frame. The number of babies varies significantly, between 10 and 50 over the 16 year study period. There is significant inter-year variation in the sex ratio of the young but this balances out to almost precisely 50/50 over the time frame. Rainfall is identified as the most significant factor affecting juvenile mortality. One of the first bats ringed in 2000 has subsequently been re-captured 47 times, had 10 babies and is at least 14 years old. 25% of Bechstein’s bats bred in their first year; 38% in their second; 28% in their third; 7% in their forth; and 2% in their fifth.

This talk highlighted the value of ringing studies – there is no other technique which would allow this data on longevity, breeding success and population dynamics to be gathered.

A standardised method for survey and monitoring of woodland bats (John Altringham)

John Altringham 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.

Advanced survey techniques for woodland bat species (Daniel Whitby)

Acoustic lures were first developed by Frank Greenaway in 2001. These are effectively speaker systems which emit high frequency calls – either recordings of bats social calls, or a digitally recreated version of these. There are now a variety available for researchers to use to increase the capture rate when trapping bats to identify, tag or ring. There is some discussion on how these lures work – studies of brown long-eared bat suggest that the lures may work be eliciting a territorial response as the capture rate was much higher in the core foraging area than the peripheral foraging area or outside of a bat’s foraging area. There are many positives to using lures. They increase the trapping rate allowing more information to be gathered in a shorter period of time and therefore causing less disturbance to local bat populations. This also makes trapping cheaper in terms of surveyor man hours. There is an increased accuracy of recording species and identifying the species assemblage present, as well as the ability to capture specific species as in the Bechstein Bat Project in the south-east. The lures also help to capture foraging bats as well as the commuting bats which are more frequently captured by mist nets and harp traps. Negatives are also to be taken into account – there is much variation in the way in which different lures work and which calls are played which may make standardisation and comparison between studies more difficult. Some lures may be limited to particular frequencies and so may miss higher frequency components of a sopcial call for example. There is a poor understanding of precisely how the lures work and the use of this technique requires more care, expertise and training than standard trapping techniques.

Reliable tree-roost indicators (Henry Andrews)

Henry Andrews, author and compilor of the Bat Tree Habitat Key ran through his top three indicators that a potential roost feature (PRF) is a roost.

The presence of actual bats came in at #3. This is because the bat may only be present for a night or two and therefore the chances of encounter are not necessarily that high. The best field sign is the longest lasting field sign and therefore, counter-intuatively, the very definite evidence of an actual bat is not number one! Care must be taken when using an endoscope with actual bats involved – a Level 2 licence (as opposed to the basic Level 1) is required to use this equipment. Henry’s number one rule is that you should never touch the bat. Henry offered the guidance that an inspection of a PRF should take 30 seconds – 1 minute and that the bat should remain lit for no more than 10 seconds.

In at #2 is the presence of droppings as these often remain when the bat has left. DNA analysis of droppings can give you a confident identification of the species for a very cheap price – around £45 from Warwick University – and therefore a dropping can be as good as a bat. Look for droppings in spiders webs (which often preserve dropping intact), on leaves, branches or any surface below the roost entrance. Sycamores are particularly good as their leaves are sticky!

The #1 indicator is substrate condition because bats modify a PRF in ways which no other species do. Smooth, bobbled, bumpy, waxy, blackened and polished surfaces inside the PRF indicate the presence of bats. These characters are best described with photographs to aid understanding – there are many example photographs and more information on these features in the Bat Tree Habitat Key – a free download.

The Warwickshire Barbastelle Project (Lois Browne)

Lois Browne gave an inspiring talk on the Warwickshire Barbastelle Project which has been running in Warwickshire for the last two years. This project studied the behaviour and habits of one of the rarest bat species in the UK through trapping and radio-tracking as well as traditional acoustic survey techniques. The study colony roosts in an ancient woodland site but forages further afield, leaving the woods and foraging in a valley to the south as well as around lakes and woodland fragments within 5km of the roost. Non-breeding bats were found to travel further to feed; up to 7km from the roost. Some bats were found to have very traditional routes which they stuck to each evening when they left the wood to reach their foraging grounds. Boxes erected as part of the project were used by the barbastelles, including use by maternity colonies. They found the Colin Morris design to be used preferentially. The project also carried out targeted work to enhance the local habitat for barbastelles, informed by the findings of their study. So far they have planted 800m of hedgerows and standards to improve connectivity, are developing three new wildflower meadows and have built a new pond.

The ecological effects of woodland management (Keith Kirby)

Oliver Rackham’s talk illuminated the way in which all of our woodlands were historically managed and that this human interaction has shaped their structure for centuries. Keith Kirby provided an overview of the ways in which management affects the ecological character of a woodland.

Planting of trees affects species composition which has a significant effect on the associated specialist species, lichens, the abundance of flora below the trees, the nature of leaf litter, deadwood and shade.

Management affects the age structure of the wood through selective felling and other management techniques such as coppicing. It also affects the spatial structure, by which parcels of the woodland are managed, and the vertical structure which affects the species composition which uses them.

Natural deadwood levels on the forest floor are around 100 cubic metres/ha whereas a worked coppice has <10 cubic metres/ha and minimal intervention areas typically have 30-50 cubic metres/ha. This significantly affects the invertebrate and saprophytic communities which are present.

New forest woodland

Management of herbivores also affects the woodland structure and character. Since we have effectively wiped out any large predators in the UK, humans are left as the only effective managers of species such as deer which have hugely complex impacts and interactions on a woodland.

Finally, all of these management decisions interact with other factors, such as climate change and nutrient levels, as well as each other. This whistle-stop tour through the ecological impacts of our management reflects the importance of taking the requirements of bats into account when considering how to maintain a woodland.

The principles of ancient woodland restoration (Jeremy Evans)

Planted Ancient Woodland Sites (PAWS) are current plantations – such as coniferous forestry – which occupy the footprints of ancient woodlands which are defined as those which have maintained continuous woodland cover since 1600. The Woodland Trust takes the view that these are ‘damaged but now written off’ and Jeremy Evans talked about the strategy which the Trust takes to restoring these sites. First they identify remnant ancient woodland features which might include ancient woodland flora, old pre-plantation deadwood, archaeological remains or mature oak coppices. The level and immanency of the threat which these features are under is then identified and actions prioritised to take the most at-risk features out of immediate danger. This might include releasing old coppices from out-shading by halo thinning, or selective thinning to bolster the woodland flora. Once these remnant features are secure, Phase 2 is the movement towards a semi-natural composition through thinning, small-scale selective fells and restoration with native trees. The activities are planned, observed and recorded throughout so that the success can be monitored and feed into future restorations.

The Countryside Stewardship Scheme, woodland management and bats (Mike Render and Carol Williams)

The main priority of the Countryside Stewardship Scheme will be to deliver the objectives of Biodiversity 2020 where the success or failures of different species will be the litmus test for success. 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. Grants will be available within the scheme for woodland creation and management as well as measures to address tree health issues and all of these interventions may serve to benefit bat species falling within the mosaic approach.

Species which are of higher conservation concern would also be catered for through the Bespoke approach – this would involve the development of prescriptions for habitat creation and management specifically designed to benefit these rarer species. The prescriptions will be developed by NE species specialists with input from the BCT whose roost data will be used to identify hotspots for site specific and landscape level interventions. Species falling within this Bespoke approach would include greater horseshoe, lesser horseshoe, grey long-eared and Bechstein’s bats – there are ongoing discussions as to whether barbastelle bats may also qualify for the Bespoke interventions.

Management risk: We must open our eyes and make significant changes to accepted and widely practiced forest management in the UK – diversification of tree species and genetics within species (John Weir)

Two thirds of woodland in the UK is broadleaf woodland and 70% of the canopy cover of these woodlands are made up of just five species. Oak represents 32% of our trees; ash and beech cover 14% each; sycamore is 11% and birch is 6%. Sweet chestnut, alder, hazel and willow are the next four species in line. This dominance of a small number of species means that diseases and pests could lead to dramatic impacts upon our woodlands – Dutch elm showed that an entire species can be all but wiped out by disease. One of the reasons why the English elm was so susceptible was that its ecology and past management meant that many trees in an area were genetically identical and so there was less scope for resistance than would be expected – this issue is relevant today with mass plantations of nursery stock trees, often imported from the continent leading to the globalisation of tree disease. The graphs showing incidences of pests and diseases in recent years is truly terrifying.

Increasing incidence of tree disease and pathogens - image from John Weir's powerpoint talk
Increasing incidence of tree disease and pathogens – image from John Weir’s powerpoint talk

Climate change is another issue which is destined to affect all aspects of ecology within the UK over the next few decades and woodland is no exception. John posited the assisted migration of native trees as a way to help woodlands to adapt to this change. This would involve the supplementing of trees of local provenance with trees originating from 2-5 degrees south which will have developed in similar climatic conditions to those which will prevail in the future. They will be better adapted to the warmer climate and the likely increases in droughts which will accompany it.

The susceptibility of our woodlands is something which we need to acknowledge and begin to address to minimise the risk and mitigate the impacts which will have huge knock-on effects to the species which depend upon them, including bats. The powerpoint of John’s talk is available here.

The use of woodlands by bats in anthropogenic landscapes – implications for policy and practice (Kirsty Park)

During the summer, female bats band together in maternity colonies to bring up their young. Previous studies have found that Daubenton’s bats segregate during the maternity season so that female bats access the better quality foraging habitats whilst the males occupy less optimal habitats. One of the studies conducted at Stirling University looked at the sex ratio of bats in urban woodlands – females were found in better quality habitats with mature trees, an open story, a more compact shape and better connections with other woodlands whilst males were found in a much wider range of woodlands. Kirsty’s talk also touched on the use of plantation woodlands by bats – these are generally considered to be less favoured but initial results of an ongoing study found a 30% greater number of echolocation calls recorded in plantation compared with broadleaf woodland sites – primarily soprano pipistrelles including lactating females. This indicates that our view of the relative value of woodland types for bats may need to be re-assessed with increased research.

Wood pasture and woodland bats – restoring the first without losing the second. Lessons from Croft Castle, Herefordshire. (David Bullock)

Oliver Rackham’s talk earlier in the day highlighted the prevalence of ancient trees outside of woodlands and subsequent talks expanded on this to identify the development of woodland around ancient trees as a threat which can lead to their decline and death through competition and shading. At Croft Castle, the National Trust are aiming to fell the coniferous plantation around retained ancient and veteran trees to restore the habitat to a wood pasture habitat with mature trees and grassland which supports many rare lower plant species and invertebrates. This conservation objective would serve a range of species but there would be impacts upon the existing assemblage of bat species – including rare species such as the lesser horseshoe and barbastelle – which favour the woodland habitat which is on site at present. The aim of the National Trust scheme is to retain habitat and linkages for the bat species, through the retention of large western hemlock corridors through the re-created parkland to ensure continuity of woodland habitat. The Trust will track the distribution and abundance of bats in 2015 and beyond in order to monitor and assess the success of this strategy.

Integrating bat conservation into multi-objective woodland management – a case study focussing on Swanton Novers Woods (Ash Murray)

Ash Murray presented a case study on woodland management for bats focussing on Swanton Novers Woods in Norfolk. Different management creates woodlands with varying benefits for bats – active coppicing provides good foraging habitat but poor roosts whilst neglected coppices are the opposite. High forest can provide both good foraging and good roosting habitat but this is not viable as cover across a managed, working woodland. The strategy taken to address this is managing the woodland in varying ways throughout the site including short, medium and long-term coppice, high forest, minimum intervention and Planted Ancient Woodland restoration. The Great Wood is managed on a commercial basis to support the conservation objectives of the wood (designated as a National Nature Reserve) and this multi-objective mosaic approach to management ensures continuity of resource for roosting and foraging bats as well as the vast number of other species which depend upon the woodland.

Social structure of bats in Wytham Woods

This final talk was a deviation from the published programme but was a fascinating way to end the day. Wytham Woods in Oxfordshire is owned by Oxford University and is said to be the most studied woodland in the UK. There are 1273 Schwegler bird boxes within the woodland which are monitored for the nesting bird species. But after the birds have finished nesting and vacate the boxes, the bats move in for the summer– 1051 roosts have been recorded representing 82% of the boxes within the woodland. Those not used tend to be those along edges with boxes in other habitats – ranging from ancient woodland, plantation and rides – being frequently occupied. From extensive surveys, the researchers identified that 13 checks were required to confirm a roost using a saturation curve assessment.

Natterer’s, Daubenton’s and brown long-eared bats are the three key species with a further five species also recorded using the boxes. The three key species have different social structures, as revealed by ringing surveys. The ~600 Natterer’s bats exist in seven different colonies within the woodland and both males and females very rarely mix with other colonies. The ~600 Daubenton’s bats have 5-6 female colonies which rarely mix, although the males move between the different colonies and sometimes form large bachelor roosts of up to 62 bats. The ~400 brown long-eared bats have 21 different colonies through the woodland and they don’t mix at all.

This complex social structure needs to be understood if the impacts of management are to be truly understood – the coppicing of one area of woodland may remove the core foraging habitat for an entire colony and this was found to happen during the monitoring and the colony had to move to a different area of the wood.

Common Pipistrelle

BCT National Bat Conference 2014

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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.

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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 Group – Brum 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.

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Midlands Bat Conference 2014

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The Bat Conservation Trust runs an annual Bat Conference in September each year which is attended by bat groups, enthusiasts and professionals from around the country. They also hold regional conferences once every two years and this year’s Midlands conference was at the end of April. The focus of the conference is not exclusively based in the region, but has talks from local bat group members and researchers as well as spotlight talks from the various bat groups in a region so that neighbouring groups can find out about projects which others in the area are involved in.

Morgan Bowers talking about the Brumbats Flight Cage at the BCT Midlands Bat Conference 2014 (image borrowed from the BCT Twitter feed)
Morgan Bowers talking about the Brumbats Flight Cage at the BCT Midlands Bat Conference 2014 (image borrowed from the BCT Twitter feed)

The Warwickshire Barbastelle Project

Lois Browne gave an inspiring talk on the Warwickshire Barbastelle Project which has been running in Warwickshire for the last two years. This project studied the behaviour and habits of one of the rarest bat species in the UK through trapping and radio-tracking as well as traditional acoustic survey techniques. The study colony roosts in an ancient woodland site but forages further afield, leaving the woods and foraging in a valley to the south as well as around lakes and woodland fragments within 5km of the roost. Non-breeding bats were found to travel further to feed; up to 7km from the roost. Some bats were found to have very traditional routes which they stuck to each evening when they left the wood to reach their foraging grounds. Boxes erected as part of the project were used by the barbastelles, including use by maternity colonies. They found the Colin Morris design to be used preferentially. The project also carried out targeted work to enhance the local habitat for barbastelles, informed by the findings of their study. So far they have planted 800m of hedgerows and standards to improve connectivity, are developing three new wildflower meadows and have built a new pond.

Emergence behaviour of Natterer’s and brown long-eared bats

Rachel Fryer gave a talk on the emergence behaviour of Natterer’s and brown long-eared bats. She observed two known maternity roosts once a week between May and September and recorded each emerging bat to identify the earliest emergence time, the median emergence time and the number of bats emerging, and correlated this with environmental variables. The earliest emergence times proved interesting with records earlier than the textbook examples. The median emergence time for Natterer’s was 60-64 minutes after sunset whilst brown long-eared bats left a little earlier with a median emergence time of 44-49 minutes after sunset. The number of bats emerging were found to fluctuate between nights – this could relate to some bats remaining in the roost or the colony being split between different roost sites. However, there was a correlation between the number of brown long-eared bats emerging and the average wind speed with fewer bats emerging on windier nights. The light levels also seem to influence emergence behaviour with brown long-eared bats emerging later under higher light levels; and Natterer’s bats emerging earlier when there was higher cloud cover. This empirical information on the emergence characteristics is valuable as existing published information is often sparse and often doesn’t specify whether the time relates to the earliest or the median emergence time.

Species Distribution Modelling for Bechstein’s Bats

A talk given on behalf of Lia Gilmour from the University of Bristol shared the results of Species Distribution Modelling of Bechstein’s bats and the use of the results to identify further suitable habitat for this rare species. The principle behind this modelling is to look at the conditions in which the bats are found and identify further locations where these conditions are present. In theory therefore, if the SDM is modelling correctly, the bats may be found in these locations. This model found four key variables which appeared to be important: the presence of broadleaf/mixed woodland, a relatively low summer rainfall, a minimum January temperature of >7 degrees and a relatively high temperature range. This corresponds well with the southern distribution of this woodland dwelling bat. The model appeared to work well as new records were found to fall within the optimal or marginal suitability distributions predicted by the model. This is a valuable tool in targeting the search for further Bechstein’s colonies to those locations where the bats are most likely to be found. It will however only identify further habitat like the ones in the bats are known to dwell and so new colonies may still be found in unexpected locations outside of the current or accepted range. This problem is further exacerbated for the Bechstein’s as so much of the distribution is known from targeted surveys using acoustic lures to capture and identify the bats. These surveys were largely carried out in locations where the bats were most likely to be found – specifically broadleaf woodland sites in the south of the country and this will have influenced, in turn, the predictions of the models. It is a case of don’t look; don’t find and the risk with this approach is that more borderline sites may be overlooked if the limitations of the methodology are not appreciated.

Alcathoe Bat in the UK

Phil Brown has been undertaking research using DNA analysis of small myotis species bats. A cryptic species was recently identified in 2010 called the Alcathoe bat which is very similar to Brandt’s and Whiskered bats and, whilst known on the continent since 2001, was not known to exist in England. One of the aims of Phil’s research was to see whether these bats could be identified outside of their current known range of Sussex, Surrey and North Yorkshire. 70 sites were surveyed and 395 bats were caught of which 39 were whiskered/Brandt’s/Alcathoe (WAB). This targeted capture and DNA collection was supplemented by samples sent in by other bat workers around the country with the result that a total of 110 WAB samples were tested. 95 of these were found to be whiskered bats; 10 were found to be Brandt’s bats; and 5 were found to be Alcathoe. Sadly, these five bats were all found in Sussex/Surrey and so there remain no records in between their current known locations towards the north and south of the country.

Brumbats Flight Cage

Morgan Bowers from Brumbats gave an inspirational and enlightening talk on the new flight cage they have had built. This allows the bat carers to assess the health and abilities of rescued bats, gives the bats opportunity to exercise and to behave in a more natural manner, and allows them to be rehabilitated and soft-released with a more supportive environment if they take a little longer to build their abilities. This also saves the perennial bat carer issue of bats getting loose in the house and hiding in the most unlikely places – including inside a hoover! The flight cage is a good training tool as well as it offers a safe environment for new bat carers to learn their rehabilitation and handling skills. You can find out more about the flight cage here with some videos to watch too! Another blog on the conference can be found on the Brumbats page here.

White Nose Syndrome in the UK

The last talk of the day was given by Alex Barlow on White Nose Syndrome in the UK. This is a devastating disease in the USA which has seen mortality rates in hibernation sites of 97% for the little brown bat and 49% for the big brown bat. The syndrome is caused by a fungus which infects the bats and gives a characteristic white nose where the mycelium grows. The presence of the fungus leads to increased evapotranspiration and loss of electrolytes which effectively dehydrates the bat and it rouses out of torpor to drink – some bats have even been observed trying to eat snow. The survival of a bat through the winter is a finely balanced process and this wakening uses a large amount of the winter reserves of the bats which then can not find food to replace the energy they have lost. There were serious fears that this disease may spread to other locations but surveys and sampling across Europe have found the fungus but have not recorded any associated mass mortality events. DNA analysis of the fungus has found significant genetic diversity in Europe which suggests that it is endemic to the continent, whilst those in the USA are all genetically similar, suggesting it is a recent introduction. This may mean that the European bats have co-evolved alongside the fungus and will therefore be able to cope with it, whilst it is a novel pathogen to bats in the US and they have suffered badly from its effects. Further active surveys for the fungus are taking place through 2013/14 with 25 sites selected across the UK, especially those used for tourism or caving. The current state of knowledge allows us to be cautiously optimistic that this fungus should not lead to the same level of devastation in the UK as has been seen in the US.

Spotlight Talks on Local Bat Groups

The spotlight talks from the local bat ground included Lincolnshire all the way across to Warwickshire, Worcestershire and Derbyshire taking in Leicester and Rutland, Nottinghamshire and Birmingham and the Black Country on the way. A range of projects are underway including NBMP monitoring of roosts; the Nathusius pipistrelle project for which Nottinghamshire and Derbyshire are amongst the pilot groups; the BrumBats Batlas project which aims to extend their knowledge of bat distribution across the area; and a range of public engagement events including bat walks and talks. For more information on the activities of all of these groups, check their pages which are all linked above. Whatever your level of interest, there will be something to get involved with wherever in the Midlands you are!

BCT Artificial Light and Wildlife Symposium 2014

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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.

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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!

Don’t forget the bats in National Nestbox Week!

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This week is National Nestbox Week which encourages people to put up nest boxes in their gardens. This is a great idea and focuses attention on providing these features as the birds first start to pair up and scope out nest sites. We have birds nesting in various locations around the garden but, for some reason, I had never got around to adding some more purpose built nesting habitats for them – something I have now rectified!

But why stop at providing habitat for garden birds? Don’t forget that gardens are vital to some of our most common bat species, such as the common pipistrelle and the brown long-eared. Attract bats to your garden and you will be able to watch fantastic aerial displays as the sun goes down throughout the summer. There are lots of tips from the BCT on how to attract bats to your garden.

There are many designs of bat box on the market and plenty of designs which you can make for yourself. I realised that the offcuts of wood we had in the shed provided everything I needed to make a Kent Bat Box – one of the simplest designs and one I would strongly recommend to anybody putting one together for the first time. This box is very simple and creates cavities which small bats such as common pipistrelle can use as a roost. This video shows the kind of tight niches which are used by pipistrelle bats.

Bats fly in the garden regularly throughout the summer and one of them – probably a brown long-eared – uses the porch as a feeding perch. I know this from the little piles of moth wings which suddenly appear some mornings, often 5-10 of them. The bats bite off the wings of the moths they have captured, eating only the nutritious bodies of the moths and leaving the wings to flutter down. Just opposite the porch is a holly tree and this struck me as the ideal place to put a box, seeing as I know the bats use this little niche of the house and garden.

Moth wings in the porch - they have caught on the spider's web on their way down but there are tell-tale signs that a bat is responsible - especially as so many appear overnight in a single night!
Moth wings in the porch – they have caught on the spider’s web on their way down but there are tell-tale signs that a bat is responsible – especially as so many appear overnight in a single night!

I also put up another box on the tree beside it, facing the opposite direction. We were recently called out to climb a tree to check a bat box where the tree was to be removed. The bat box had only been up for a few months and was clearly un-used so we were able to inspect it and take it down without causing disturbance to any bats. There was nowhere else on the site to place the box so I have put it up in the garden instead – I am interested to see if either of the boxes are used and whether a particular design might be preferred.

If you are putting up a bat box, make sure it is high above the ground (at least 4m if possible) to deter predators and ensure that there is not too much disturbance to the bats as you use the garden. Another important point is to ensure that there is a good fly-in and fly-out route for the bats. This can be achieved by imagining the bats dropping from the entrance in an arc which is 1-2m out and 2-3m down. If you have left this space for them, they should be able to enter and exit the box. Another important point is to allow them to emerge into some cover, if possible, or out along a hedge or tree line. Bats use these vegetative features for commuting around the landscape and placing your box in such a location should increase the chances of a bat moving in.

The designs for the Kent Bat Box can be found here and all you need is a plank of wood, some smaller wood for battons, a saw and a drill (or hammer and nails). The design is very simple to follow but below shows the step-by-step progress of the construction.

The log shed with offcuts we've been given for the log burner - but there is a Bat Box there just waiting to be built!
The log shed with offcuts we’ve been given for the log burner – but there is a Bat Box there just waiting to be built!
The constituant parts of the Kent Bat Box, cut to size. At the bottom you can see the three boards of varying lengths, at the top right is the top for the box, top left are the battons used to create the cavities.
The constituant parts of the Kent Bat Box, cut to size. At the bottom you can see the three boards of varying lengths, at the top right is the top for the box, top left are the battons used to create the cavities.
This shows how the main pieces fit together - the battons are attached to the long-sides of the boards which are going to be placed one on top of the other onto the longest back-board.
This shows how the main pieces fit together – the battons are attached to the long-sides of the boards which are going to be placed one on top of the other onto the longest back-board.
The pieces constructed in the last image are placed, one on top of the other, with the smallest at the top and the largest (the backboard) at the bottom to create the two cavities which will form the roosting sites for the bats. These are drilled securely together.
The pieces constructed in the last image are placed, one on top of the other, with the smallest at the top and the largest (the backboard) at the bottom to create the two cavities which will form the roosting sites for the bats. These are drilled securely together.
Attach the top. As with all bat boxes, the crevices will be downwards facing as bats will land and climb up int the crevices to roost. The top will keep the cavities dry.
Attach the top. As with all bat boxes, the crevices will be downwards facing as bats will land and climb up int the crevices to roost. The top will keep the cavities dry.
A view from the base of the Kent Bat Box showing the crevices which will for the roosting opportunities for the bats.
A view from the base of the Kent Bat Box showing the crevices which will for the roosting opportunities for the bats.
The chosen location for the bat box - after a bit of 'gardening' to clear leaves and twigs away from the fly-in to the box.
The chosen location for the bat box – after a bit of ‘gardening’ to clear leaves and twigs away from the fly-in to the box.
The new bat box securely attached using a bungee cord to ensure that the fixing does not damage the tree as it grows. The box is about 4m off the ground with a clear fly-in below, opening onto further shrubs and cover for the bats.
The new bat box securely attached using a bungee cord to ensure that the fixing does not damage the tree as it grows. The box is about 4m off the ground with a clear fly-in below, opening onto further shrubs and cover for the bats.

BCT Bat Conference 2013

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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!