Protecting and monitoring Scotland's bat hibernacula

This article was first published in the April 2015 edition of Recorder News,  the magazine of BRISC - Biological Recording in Scotland (www.brisc.org.uk)

As a bat specialist I am regularly asked why bats are protected when they seem to be quite common. To the uninitiated a bat is just a bat, but we have at least ten species in Scotland and whilst some are relatively common several are much rarer. 

Bat populations today are a fraction of what they were a few decades ago and, whilst the decline of some species appears to have slowed, recovery to previous population levels is a long way off. Even the Soprano Pipistrelle (Pipistrellus pygmaeus)and Common Pipistrelle (P. pipistrellus), our two commonest Scottish bat species and most often seen due to its habit of emerging before full darkness, face a plethora of threats.

What often isn’t recognised is the vulnerability of bats in our temperate climate. The females of most Scottish bat species are only capable of giving birth to one juvenile per year (Noctules are an exception, occasionally having twins). From the moment of birth the clock is ticking and time is against each tiny and utterly dependent baby bat. They have to grow at a prodigious rate from birth in June to be ready to fly around two months later. They then have to rapidly climb a massive learning: in around three months not only do they have to learn to fly with sufficient skill and agility to outwit and capture their insect prey but they need to do so with sufficient proficiency to rapidly build fat reserves in readiness for hibernation.  Insufficient fat will result in a failure to survive hibernation. 

It’s no easier for the adults. Females spent the summer devoting all their energy to hunting and feeding their young and now they too have a limited time to build fat reserves. Males have an easier summer but must work hard through autumn, attracting females to mate before they hibernate too.

Scottish bats live on a knife-edge at the best of times, so the negative effects of human activity are especially pronounced. Agricultural pesticides and development have reduced hunting habitat and prey availability. Timber treatment of older buildings has been harmful to attic-roosting bats (though the worst chemicals are now banned). Conversion of old agricultural and industrial buildings has removed many roosting opportunities and though legislation protects roosts in buildings from disturbance or destruction, implementation of the law varies from local authority to local authority. Fragmentation of habitat is especially problematic for bats: a single bat colony may use dozens of roosts for different purposes through the year and they need safe commuting routes to link these with each other and with suitable foraging habitat. Removal of hedgerows and tree-lines reduces their ability to commute freely between these locations. Sadly, deliberate destruction of bat roosts by indifferent or ill-informed people is far from unknown.

 A hibernating Brown Long-eared Bat (Plecotus auritus)

During hibernation bats enter a condition of deep torpor, reducing their body temperature to between 2 and 8 degrees Celsius, slowing their heart rate to as little at 10 beats per hour and breathing perhaps once per hour. This reduces their use of stored energy to the minimum that supports life. But hibernation is not continuous and bats regularly wake, sometimes moving location. They may even hunt if the weather is warmer and Pipistrelles are occasionally seen in daytime, hunting for winter-flying insects in the midday sun. However arousal from deep torpor is expensive in energy and being forced to arouse by disturbance can reduce a bat’s ability to survive hibernation.

Conditions within hibernacula are critically important. Temperature must be steady, usually between 2 and 8 degrees Celsius. High humidity minimises water loss, reducing the need for bats to arouse to drink. It can take up to half an hour for a bat to arouse from deep torpor, so safety from predators is important, as is a lack of human disturbance. Hibernation tales place in differing locations, depending on the bat species. Noctules (Nyctalus noctula) and Leisler’s Bats (N. leisleri) tend to hibernate in deep tree holes, Pipistrelles (Pipistrellus sp.) often use crevices in buildings, cliffs or under loose tree bark which, whilst appearing relatively exposed, contain a suitable microclimate. Underground hibernacula such as caves, mines and tunnels tend to be used by bats of the Myotis genus - Daubenton’s (M. daubentonii), Natterer’s (M. nattereri), Whiskered (M. mystacinus) and Brandt’s (M. brandtii) - and Brown Long-eared Bats (Plecotus auritus).  

Man-made or natural underground sites with suitable conditions for hibernation are uncommon and increasingly under threat. In the Lothians disused limestone mines are well-used and are usually located at the base of quarries. Out of six mines known to be used by hibernating bats one is regularly disturbed by members of the public, one is unsafe due to vibration from an adjacent land-fill site and the landowner at another site recently had to be warned by SEPA to cease illegal landfill activity.

The quarry at Hope Mine, near Pathhead was filled in during the 1990’s and 2000’s. Access for bats was maintained via a grilled access hole. Airflow is critical in underground hibernacula: warm, stale air needs to be continually vented to maintain suitable hibernation conditions. At Hope a subsequent underground rock-fall and lack of maintenance of the air vent installed in the 1980s has caused the temperature underground to reach levels of over 14 degrees, rendering the mine unusable by hibernating bats.

There is a happier story at the remaining two mines. Middleton Upper Quarry near Gorebridge has recently been filled with over 600,000 tonnes of spoil from the Borders Railway. My company (David Dodds Associates Ltd.) worked closely with NWH Group, the owners and operators of the site. We used acoustic monitoring to assess which access tunnels were favoured by bats entering and leaving the disused mine workings. Under a Scottish Natural Heritage derogation license NWH staff used gabion baskets to create a safe access route for bats to continue accessing the mine after the quarry was filled in. Although the appearance of the site has changed considerably, a section of cliff face above the favoured entrance has been retained and stabilised, acting as a sign-post towards the entrance favoured by the bats.  The position of this entrance within the mine allows warm air to vent naturally, but an additional ventilation pipe has also been installed to ensure that temperature conditions remain suitable should that change. I’m happy to say that the first underground survey, during January 2015 showed that the mine continues to be used by Natterer’s, Daubenton’s and Brown Long-eared Bats.  We hope to use a similar approach to the adjacent Middleton Lower Quarry in due course.

Middleton Upper Quarry - an underground hibernaculum successfully safeguarded 

(photo courtesy of Birch Tree Images www.birchtreeimagesphotography.co.uk)

The National Bat Monitoring Programme (NBMP) is managed by the Bat Conservation Trust (BCT) on behalf of a partnership including BCT and the Joint Nature Conservation Committee (JNCC). This programme is an excellent example of citizen science at its very best. Throughout each year volunteers all over the UK carry out a variety of different bat surveys, from walked transects in open country or along watercourses, to counts of bats emerging at known roosts and searches for bats swarming at roosts at dawn. 

The slow and difficult search for hibernating bats

(photo courtesy of Birch Tree Images www.birchtreeimagesphotography.co.uk)

The surveys are designed to allow anyone to make a contribution, from those with virtually no experience of bats to skilled, licensed bat-workers. The NBMP website includes training materials and bat detector training courses are regularly run, to ensure as many people as possible take part. The NBMP data is collated and used to provide a statistically robust assessment of how bat populations are faring in the UK and in Scotland where sufficient data is available (more volunteer surveyors are urgently needed by the NBMP in Scotland), published each year as “The State of the UK’s Bats” and is widely used to inform and target bat conservation effort.  It also forms on of the UK Government’s biodiversity indicators.

One NBMP survey method which requires especial skill and experience is hibernaculum counts. These must be carried out by bat-workers who are specifically licensed for hibernaculum work, usually assisted by small teams of dedicated volunteers. This is not easy work. Underground hibernacula are often muddy, wet and physically demanding to access and to move around in. Safety equipment is paramount and surveyors need to be suitably trained and equipped to cope with conditions underground. Underground hibernacula may be natural caves or man-made structures, such as tunnels, mine-workings etc. The latter are usually disused and a continual assessment must be made as to whether a hibernaculum is safe to survey. Bat conservation is important, but human health and safety is always the priority.

Bats in Scottish underground hibernacula are usually found on their own, or very occasionally in small groups. Often they are dispersed throughout a large area and it is not unusual for a team of four surveyors to spend several hours searching to find only a handful of bats. Depending on the temperature and humidity conditions in a particular hibernaculum bats may be found on roofs or walls but often they are concealed within cracks and crevices, where they can find security from disturbance and a suitable microclimate. It is rarely possible to fully census bats within a hibernaculum, as many individuals may be invisible in deeper crevices or in areas unsafe to survey or in some cases mine-workings are simply too large to survey comprehensively. To ensure that data used by the NBMP is as robust as possible a repeatable survey method is used: as far as possible each year’s surveys will be done by the same number of people, with a similar mix of experience, spending a similar amount of time on the survey and following the same route through the hibernaculum. Although a long, hard survey may yield only a handful of records of bats, when combined with dozens of other surveys around the country and compared year-on-year useful population data starts to emerge.

Great effort is taken to ensure that disturbance of bats during a hibernaculum survey is kept to an absolute minimum.  Surveys are normally carried out twice each winter, with several weeks gap. Noise is kept as low as possible and bats are illuminated with torches only for as long as it takes to identify them. Bats are never normally touched or handled and in more confined spaces care is taken to avoid standing below hibernating bats or breathing on them, to avoid the surveyor’s body temperature from having an impact.

A hibernating Natterer's Bat (Myotis nattereri)

Identifying bats within hibernacula is challenging and requires a good deal of experience. Critical identification characteristics are often invisible without handling a bat or hidden by the crevice the bat is in. Surveyors are forced to use secondary identification characteristics such as fur colour, face and ear shape, size of feet etc., all of which are difficult to measure except on the basis of experience. Often it is only possible to identify a bat to genus.

It isn’t usually possible to identify individual bats, especially in hibernation when wings are tightly folded so that scars to the wing membrane cannot be seen. It is possible to ring bats using loose, horseshoe-shaped aluminium rings around the forearm, but this technique is used more sparingly than for birds due to potential impacts on the bats, so it is rare to see a ringed bat within a hibernaculum. In January 2010 I found a Daubenton’s Bat hibernating in a tunnel high in the Lowther Hills. This bat not only had a ring but also had most of one ear missing. “one-ear”, as she became known had been rung by researchers working on behalf of Scottish Natural Heritage, testing for rabies at Falls of Clyde nature reserve 35km away in August 2009.  Her injury seems not to have prejudiced her ability to hunt successfully, as I have regularly recorded her hibernating in the same place in the five years since then.

"One-ear" in hibernation. Her missing right ear and the ring on her forearm are clearly visible, as is condensation on her pelage.

It cannot be stressed highly enough how important hibernacula are for bats in Scotland. The need for sites with stable, low temperature and high humidity, combined with long-term security and lack of disturbance means that suitable sites are not common and it is common for bats to travel long distances to reach them. Finding and monitoring these sites is essential if we are to protect them and to measure variation in bat populations. Destruction of hibernacula is just one of many threats faced by our bats and protecting their ability to hibernate safely is critical for the long-term survival of these sensitive, vulnerable and oft-maligned animals.

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Memories of Summer Bats

This post has absolutely no meaning or purpose, except that I was tidying up my hard drive and realised I had recorded several video sequences of bats in the hand over the past year or so. It's minus four outside and the only bats I have seen for a couple of months have been deep in torpor (hibernation). So, to relieve the winter blues, here are some lively, wriggling bats to enjoy...

First, a Brown Long-eared Bat (Plecotus auritus). This was one of a group of 12 in a bat box on a golf course near Edinburgh. I filmed several sequences, trying to get the bat to extend it's massive ears, but the best I could get from it was the wiggle of its ears you see here. Long-eared Bats use their ears like parabolic dishes, concentrating sounds made by prey such as harvestmen, spiders and larger moths, allowing them to minimise the intensity of their echolocation calls. Some of their prey have rudimentary hearing and this prevents them from hearing the bat's approach.

Next up is a Noctule (Nyctalus noctula). This is the biggest bat species found in the northern U.K. This female demonstrates nicely the importance of using the right hold and the correct amount of pressure when holding a bat (see the note as the end). To begin with she struggles to free herself, but she quickly realises that she is secure and relaxes.

Next is a Soprano Pipistrelle (Pipistrellus pygmaeus). It's not a particularly good video segment, but it sits quite nicely beside the previous segment as the Soprano is our smallest bat and looks tiny by comparison with the bruiser in the previous video!

Lastly, here is a longer segment of a male Whiskered Bat (Myotis mystacinus). This species is quite rare in this region, so I took the opportunity to record a video showing some of its morphological features. Whiskereds are hard to tell apart from Brandts Bat (Myotis brandtii) or Alcathoe's Bat (Myotis alcathoe). One of the best characters for telling them apart is their dentition, though examining the teeth of a small and annoyed animal isn't always easy! Sadly the camera I had available on that day wasn't capable of showing that level of detail, so you can't see the teeth very clearly.

Important note - disturbing bats in the United Kingdom or anywhere in the European Union is an offence unless you hold an appropriate license. In the UK these are issued by one of the statutory nature conservation organisations (Scottish Natural Heritage, Natural England, Countryside Council for Wales, etc). If you would like to learn to work with bats your best starting point is to contact your local bat group for help, advice and training.

See the Bat Conservation Trust Website for details of your local bat group: Local Bat Groups

My website: www.plecotus.co.uk

A Weekend With Engelbat

I once worked on a bat project with someone whose sense of humour was completely absent. Anyone who knows me will tell you that my sense of humour is ever-present and decidedly peculiar, so things would always be a little difficult! This person was adamant that individual bats should never be given names as it anthropomorphises them, though in my view giving something a name simply labels it and is harmless (it is poor interpretation of behaviour that anthropomorphises a wild animal). The result of this difference of opinion is that, in honour of the humourless one, any bat which passes through my hands is immediately given a ludicrous name. This is how Engelbat (Engelbat Humperdink? Geddit? No? See what I mean?) came to be named.

He was a juvenile Brown Long-eared Bat (Plecotus auritus), found one July morning on the ground floor of a large country house. The house has a known BLE maternity roost in the attic, four stories above, but Engelbat had wandered quite some distance from there and looked rather sorry for himself, covered in cobwebs and tucked under a radiator.

I had no way of knowing why he had left the roost. This site has no history of bats straying into the building. It's possible his mother had died, causing him to become dehydrated and leave the roost in search of water. However, as he was old enough to fly it is perhaps more likely that he got separated from his mother and simply ended up in the wrong place. I often explain to roost owners that young bats are just as likely to do something silly as young humans.

A close-up of Engelbat's wing, showing the clear patches (unossified bone) in his joints which indicate a juvenile.

I don't normally get involved in bat rehabilitation work. It's a difficult, skilled and phenomenally time-consuming job, so I normally pass casualty bats on to those dedicated individuals who excel in it (hats off to Tracey, Carol and Nigel!). However, Engelbat was a bit different in that he was several weeks old and capable of flight. he just needed some TLC and a plan to get him back into the company of his mother.

Having given him a drink of water (always the number one priority with a casualty bat - they can go a few days without food, but dehydration is a swift killer) I checked Engelbat over for signs of injury and found none. I then took him home and installed him in the bat-cage. This is simply a small plastic cage of the type used to transport hamsters etc. Inside is a shallow water-bowl, a glass jar of warm water with a towel wrapped round it (to simulate his mother) and a canvas pouch hanging on one site, to allow him to retreat out of site into a simulated crevice. He quickly grabbed onto the warm sock and settled down and I left him to get used to his new surroundings. Later he left the sock and took a drink from the bowl, before moving up into the canvas pouch: all positive signs.

Engelbat with the warm sock which acted as a mother/colony substitute.

A while later Isla and I got him out of the cage to feed and assess him. He had done a couple of droppings in the cage, indicating that his digestive system was functioning. When offered a mealworm he grabbed it with enthusiasm, but had some difficulty chewing it, a bit like a small child given a hard toffee. Mealworms are the standard food source for casualty bats, but for younger animals their tough outer skins are a bit too chewy. We tried him on "white" mealworms, i.e. those which have recently shed their skins and have not properly hardened. He found these easier, but still struggled, so from then on we fed him mostly mealworm innards. This is a delightful meal to prepare. First slice the head off a mealworm, then squeeze out its insides as though its a tube of toothpaste. The resulting blobs of vile gunk were voraciously devoured. He prove to be a slightly aggressive little bat, using his forearms to "stamp" at anyone who came too close. Male Brown Long-eareds have a reputation for being grumpy when handled and he fitted that stereotype quite well!

A brief video of Engelbat slowly munching his way through a white mealworm.

So far he ticked a lot of the boxes for being capable of rapid release: no injuries, functioning digestive system, eating and drinking well, so the final test was could he fly? He quickly demonstrated he could by flying happily round and round the living room. Brown Long-eareds are slow-flying bats, so the restricted space didn't seem to faze him at all and eventually he astonished us by managing to land and somehow grip a smooth painted wall, which I'd never seen a bat do before. Several more flights were managed with aplomb.

As he was clearly a competent flier for his age that led us towards how to restore him to his colony. Placing stray infants back into roosts is a questionable approach, as it is impossible to know whether the animals mother is still within the colony, or whether the juveniles wandering may be due to her death, for example killed by a predator. If this were the case then returning the juvenile to the roost may not be the best way forward.

After a conversation with Tracey Joliffe (a very experienced bat carer) for a second opinion, we took Engelbat back to the roost at sunset and placed him on a wooden bench which the adults fly over on their way to their feeding grounds. Our expectation was that his mother would encounter him and encourage him to fly with her. As it happened he chose to fly on his own and flew very competently along the flight line used by the colony, into the nearby woodland.

Of course it's impossible to tell the outcome of a casualty bat returned to the wild (unless you are Maggie Brown, who has done some amazing work tracking her casualties post-release, to evaluate their success). Hopefully he fed successfully and returned to the roost with the rest of the colony and hopefully he teamed up with his mother, if she was still alive. We'll never know for certain. Now I have to think up another ridiculous bat name, ready for the next bat who comes to stay...

If you're interested in caring for sick, injured or orphaned bats the best starting point is to speak to an existing bat carer, who can mentor you and help you get going. It's easy to get things wrong and sound advice and support is essential if you want to get it right. Contact your local bat group to find out who does bat care in your area. You can find your local group via the BCT website (and if you're not already a member...join!) . Another great source of information is the "Bat Rescue Manual", published by the West Yorkshire Bat Hospital, who also publish a regular newsletter: "Bat Care News". Your local bat carer will be able to put you in touch.

BCT Website: BCT Bat Groups page

My website David Dodds Ecology

An early spring...maybe?

Last night I took a group of ecology undergraduates to a 200 year-old kirk (that's church to those without a Scottish education) in East Lothian, to watch for bats. I had my fingers firmly crossed on the way there: although I know the church and churchyard to have plenty of summer bat activity it is still very early in the season for bats to be at all dependable.

In the summer the kirk has a Soprano Pipistrelle (Pipistrellus pygmaeus) maternity roost within the roof structure and also has Brown Long-eared Bats (Plecotus auritus) inside the kirk itself - during the summer there is usually a light scattering of droppings over the pews. Last year I watched one flying up and down inside the kirk, warming up before going out to forage.

The most I could really hope for was that there might be one or two individual Pipistrelles foraging around the kirkyard - it's in a secluded, tree-lined valley, alongside a burn (or stream if you prefer), so it's good foraging habitat, even this early in the season.


When we arrived and walked round there were no droppings inside the kirk, althought there were some on the exterior, making me hope that at least a few of the Pipistrelles may be present.

At sunset a few Soprano Pips overflew the kirk at first, commuting from other locations in the valley. Then there came an excited squawk over the radio, announcing that someone had seen a bat emerge from the edge of the kirk roof and we watched about 30 Sopranos emerge from the same spot where I watched several times that number come out in the autumn last year.



I am sure that there will be many more than 30 bats in that roost in mid summer, when Soprano Pipistrelle females gather in large numbers to rear their young - these are probably the first arrivals. Interestingly, we also heard a male Soprano in songflight, the string of mating calls designed to attract mates. This is primarily an autumn activity, but seems to occur a little in spring as well.

It's not hard to see why the bats are active so early in April. The chart below shows night-time temperatures at the Met Office's Gogarbank station, near Edinburgh. There have been two weeks of fairly consistent temperatures around 7 to 8 degrees, which seems to be the level at which bat activity in this area picks up. As a happy coincidence, last night was also the warmest night of the year so far.



However, this might not be the end of the story. It's still very early in the year and weather is never as reliable as we would like. As you can see below, last year April started off warm like this and then went into a cold period for a couple of weeks, causing bat activity to fall away until nearly the end of the month. Only time will tell what will happen this year.



My website: plecotus.co.uk
Contact me: mailto:blog@plecotus.co.uk

Winter Bat Activity

We tend to think of winter as a time when bats hibernate and won't be seen again until spring. In fact hibernation is not as simple as that: bats do awaken at times and move around. Indeed, they are sometimes seen flying in the midst of winter.

This afternoon whilst walking the dogs I spotted a Pipistrelle foraging over the River Esk. It was flying round in circles in the clockwork flight pattern typical of the genus and occasionally dropping down to catch an insect. A feature of winter bat activity is that it happens in daytime, as the higher ambient temperature means there is a greater likelihood of catching enough insect prey to offset the energy costs involved in coming out of hibernation.

I tried unsuccessfully to interest the dogs in the bat, as I have an idea it could be rather useful to have a dog trained to listen for bat calls and alert me when there's a bat nearby. Unfortunately, my pair of canine delinquents find the command "sit" quite challenging, so they aren't likely to succeed in training as bat-dogs.


When I passed by later on at dusk the bat was still hard at work hunting and seemed to be having some success, despite the ambient temperature being only 3 or 4 degrees. I have heard several suggestions as to why bats occasionally feed during the winter. It may be that individuals have been forced out of hibernation because they have failed to build sufficient fat reserves to see them through the winter, but it seems more likely that fluctuations in temperature may cause individuals to take advantage of the opportunity to forage on insects which have become active.

Different bat species have differing requirements for hibernation. Here in Scotland Myotis species, such as Daubenton's (Myotis daubentonii) or Natterer's Bats (M. nattereri) seem to be particularly exacting, hibernating below ground in caves and mines which feature a steady, low temperature, low airflow and high humidity. They usually hibernate in crevices or ledges where the microclimate may be particularly stable.

Brown Long-eared Bats (Plecotus auritus) are less exacting. When found underground they tend to hibernate on walls or hanging from the roof and are often closer to mine entrances than the Myotids.

The least exacting bats are the Pipistrelles, which are rarely found underground, instead selecting relatively exposed holes and crevices, which are more likely to be influenced by changes in the weather. Whether there are differences between the two Pipistrelles is difficult to judge. As they are impossible to differentiate without handling, they tend to be lumped together in hibernation surveys.

Last winter I wrote about a castle where a group of Pipistrelles and a Brown Long-eared were hibernating in crevices within a cellar (See "Hibernating Pipistrelles", February 2008). The castle sits atop a hill and there is a constant breeze blowing through the cellar. Unsurprisingly, no Myotids were found hibernating there.

A hibernating Pipistrelle

Carol and Nigel Terry, our local bat carers noted that a casualty Pipistrelle kept through the winter in a cold room tended to wake up and feed every 10-14 days. It may be that Pipistrelle autecology makes use of winter foraging opportunities and that they choose hibernation sites which better allow them to respond to these opportunities.

My website: David Dodds Ecology

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The Great Hibernaculum Hunt Revisited

A couple of times recently I've described the hibernaculum survey work I've been doing, together with several other members of Lothians Bat Group. We've been looking at potential hibernacula and sites with historical winter records of bats, in the hope of adding to our list of active hibernation sites.

The goal of all this work is to ensure that hibernacula - the most vulnerable of all bat roosts - are protected and also to to contribute as much data as possible each year to the National Bat Monitoring Programme.

(Carol Ann demonstrates how some sites are just plain awkward to access)

Having reached a stage when I've arrived at the bottom of my list of possible sites, when we're running out of winter and when frankly I've seen enough wet, muddy and claustrophobic underground places to last a lifetime, I thought it would be interesting to take stock.

Including surveys of exisiting hibernacula, both in the Lothians and in Dumfries and Galloway, in the past three months I have surveyed:

• 6 limestone mines
• 1 copper mine
• 7 lime kilns (one of them flooded to about half an inch higher than my waders!)
• 2 tunnels
• 4 castles
• 2 soutterains
• 1 WW2 underground bunker
• 2 pill-boxes
• 3 air-raid shelters

Out of all those sites, the following records were made:

• 16 Natterer's Bats (Myotis nattereri)
• 5 Daubenton's Bats (Myotis daubentonii)
• 1 Unidentified myotis bat (Myotis sp.)
• 6 Brown Long-eared Bats (Plecotus auritus)
• 16 Pipistrelles (Pipistrellus sp.)

(Two Natterer's Bats hibernating in a cave roof crevice )

The frustration is that all the bats were in the sites where we expected to find them. In other words: no, we haven't found any new hibernacula! That said, there are several sites which have strong potential and will be revisited next year. The disappointing result is probably only to be expected. Bats are extremely discerning about sites they use for hibernation: their requirements regarding temperature, humidity, constancy of both and lack of disturbance are very precise. That is exactly why it is so important to find and protect these sites.

(A Daubenton's Bat hibernating in a gap within the wall of an underground stone bothy)

So, after many days of clambering about in thick gooey mud, with chilly water running down my neck, was it all worth it? Well, yes it was. Nigel, Carol Ann, Rachel, Stuart, David, Natalie, Freda, Max, Peter and all the other bat group members I've surveyed with are great company and there's a real feeling of doing something valuable for conservation, even if it's only to strike a site off the list.

Those sites in which we didn't find any bats often produced other compensations. Amongst other things, I've seen four different Barn Owl (Tyto alba) roosts, more Roe Deer (Capreolus capreolus) than you can shake a stick at and some rather attractive grey slugs with a cream stripe (species, anyone?). Plus, loads of fascinating human history: from 3,000 year-old soutterains, through 600 year old castles to World War II bunkers and pill-boxes.

Oh, and I've got through enough Persil to sink a ship....

(Nigel, looking intrepid in a copper mine)

Please remember that hibernating bats are extremely vulnerable to disturbance. Carrying out hibernaculum surveys requires a roost visitor's licence with a specific endorsement. Entering a hibernaculum and disturbing hibernating bats is a criminal offence. Many hibernation sites are also extremely dangerous. If you are interested in doing this type of survey work contact your local bat group, who can help you to get involved legally and without risk of harming the bats or you.

Find your local bat group: http://www.bats.org.uk/batgroups/batgroups_list.asp

More information on the NBMP: http://www.bats.org.uk/nbmp/index.asp

Lothians Bat Group: http://plecotus.co.uk/page_1204624452640.html

My Website: plecotus.co.uk

Confessions of a bat surveyor

I sometimes find working with bats a little humbling. Not only is there a vast amount we don't understand about the bats here in the UK, let alone worldwide; there are many big bear-traps, waiting to catch the unwary bat surveyor. I thought I knew most of the worst ones, but today I discovered I had fallen into a trap I actually knew about, a really obvious one. Oh bum!

I think Brown Long-eared Bats (Plecotus auritus) must be my favourite bat species (hence my choice of web address). They are very attractive (by bat standards), with enormous rabbit-ears, dwarfing their bodies and a face that makes them look faintly bemused by life. Better still, they occupy a very specialised and fascinating niche: emerging late, flying slow and using their ears to listen for their prey. Not called the "whispering bat" for nothing, their echolocation is very faint, allowing them to catch those moth species which have developed rudimentary ears to help them take avoiding action when an echolocating bat is near. In short, they are nothing short of amazing.

Brown Long-eareds are generally easy to identify in Scotland: nothing else has ears anything like that size. In the South of England, things are harder as there is another long-eared bat: the Grey Long-eared Bat (Plecotus austriacus), which is extremely difficult to separate from it's brown cousin. Bat-workers there have to resort to measuring tiny parts of the bat's body to separate the two. Unfortunately, I don't have that excuse!

The trap I fell into was to identify a Brown Long-eared Bat as a Daubenton's Bat (Myotis daubentonii). How is this possible? The Daubie has tiny ears by comparison! Long-eared bats have an endearing habit of folding their ears under their wings when they go into torpor, to help them retain warmth. This leaves the tragus (the spear-like middle-part of the ear) sticking up, looking for all the world like a small ear...

In my defence, I must say that I wasn't alone, there were several (nameless) people with me on a hibernaculum survey last month, and they share in my crime! I even took a photograph of the bat in question, which, when enlarged, clearly shows the roots of the ears folded over the flanks, but it was a bit fuzzy, so I didn't look closely at it until this evening. Today we did a second survey of the hibernaculum (the National Bat Monitoring Programme requires two winter surveys, a month apart). We found a bat in a similar place, in the same attitude, yet seeming to be a different species. It seemed too much of a coincidence, so on arriving home, I checked the photographs. It's a fundamental error, but I suppose we were peering in torchlight at a bat on the roof of a mine...

Anyway, in the spirit of public humilition and restitition I hereby present my guide to not making the same mistake! The three pictures below tell the story.

Firstly, the Brown Long-eared in question. Note the wing roots folded over the flanks, the shape of the tragi (masquerading as ears) and their pale colour. If the picture looks a bit odd, it's because the camera is pointing up and zooming into a bat hanging from the roof of the mine.



Next, a Daubenton's Bat for comparison.

Finally, it's close relative and another species commonly found in our hibernacula: the Natterer's Bat (Myotis nattereri)

Now go forth and learn from my error! Mea culpa, mea culpa, mea maxima culpa.

Please remember that handling bats, disturbing them or their roosts, photographing them or surveying their hibernacula, all requires a licence. If you're interested in getting involved, join your local bat group. See here for a list of contacts: http://www.bats.org.uk/batgroups/batgroups_list.asp

For information on the National Bat Monitoring Programme (NBMP) see: http://www.bats.org.uk/nbmp

My website: http://plecotus.co.uk/