Early career ecologists - making progress in winter

Winter, hibernation season for ecologists? Not quite, but it's definitely the time to slow down, write reports, catch up on admin. and take back some of those extra hours we all work during the summer. But what if you're an early career ecologist, who either doesn't have a full-time job yet or whose seasonal role has now ended. How best can you best fill the winter months? Hopefully you've managed to earn enough in the summer to keep you going, but how best to prepare yourself for the next season?

I suspect you'll be spending an inordinate amount of time hunting the job sites, sending out CVs, crafting cover letters (a truly satanic task, if ever there was one) and praying that you'll get the job you know you deserve. Whoah! Stop that negative thought NOW - you DO deserve it. Winter is also peak the peak season for depression. 

Earlier in the year I posted some suggestions for ways to enhance your field skills and improve you chances in the job market (Field skills for early career ecologists and Early career ecologists and hamster-powered scootering). So what can you do to enhance your employability when the weather is wet and grubby and all the interesting wildlife is hibernating (I'm a bat specialist, so that may be a slightly biased view)? 

Here's a thought - how are your bryophyte ID skills? Many moons ago I recall standing, huddled together in the rain with a group of fellow-sufferers whilst Nick Hodgetts bounded enthusiastically around an embankment, showing us different bryophyte species (Nick's a brilliant tutor by the way, and I can recommend the courses he leads). The fact is that bryophytes are often at their best when wet and some species are especially useful for habitat indication. I wrote a post about a few commoner bryophytes a few years back (Right-diddly-wotsit-squirrelly) Since then the British Bryological Society have completed their superlative field guide and I'm happy to say it's very user-friendly and a great addition to your christmas list.

A former member of my survey team got his first break into what has subsequently been a successful career in professional ecology, when he turned up to an interview and was handed a bag full of plant material and asked what he could ID from it. The first thing he noticed was Polytrichum commune - a large and striking moorland moss which, as luck would have it, I'd pointed out to him during an especially boring transect the evening before. Lucky or what? So don't neglect bryophytes! They have a charm all their own.

If you're a member of your local bat group now is the time to start asking about hibernation surveys. Be persistent and make sure they know how keen you are, because for many underground sites numbers need to be limited, to minimise disturbance. Data from these surveys feeds into the critically important National bat monitoring programme and, after having to shelve surveys last winter due to Covid it's really important to gather data this winter (though there's a new risk assessment process). You do, of course, need to accompany someone with an appropriate bat license and not just for legal reasons - underground sites are dangerous. There's more about bat hibernation surveys here: The great hibernaculum hunt and here: The great hibernaculum hunt revisited.

How are your GIS skills? When the weather is miserable, why not delve into QGIS, the free open-access GIS system which has become ever more popular over the past few years? GIS is a core skill for a lot of ecology work and if you're new to QGIS there are many free resources to help you work your way into QGIS. Take a look at The QGIS project.

Finally, winter weather isn't all bad news and there is nothing like freshly fallen snow for finding and identifying animal tracks - another very useful field skill. There are quite a few guides available, but my favourite is Preben Bang and Preben Dahlstrom's book, which has been in print since forever - I remember borrowing an early edition from the library when I was a teenager in the 1970s (the late 1970s, just to be clear!). Don't be put off by the Ray Mears celebrity gimmick on the current edition, it's a really good field guide and well worth hinting to Santa about.

One final thought - when you get that interview and you're sat there, suited and booted and quivering slightly with fear tell them about all the stuff you've done. Maybe it's a British thing, but far too many interviewees assume anything they've done probably isn't good enough and keep quiet about it unless there's a formal certificate or diploma. Take confidence in what you can achieve on your own and in what you have achieved. To prove my point, have a read of Ash Ronaldson's guest blog - Paid bat surveying is an actual, real thing - Ash's first season. Ash has just accepted a full-time job as an Assistant Ecologist. See?

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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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The return of "one-ear"

Each winter I regularly don my hard hat, waterproofs, torches etc and deliberately choose to descend into dark, wet, muddy and essentially unpleasant places. Hardly the act of a sane adult, but then nobody's ever accused me of being one of them! Surveying underground bat hibernacula (places used by hibernating bats) provides survey data for the National Bat Monitoring Programme (NBMP), creating useful information about bat population change. I am also undertaking a long-term study of how bats vary their use of underground sites through the hibernation period.

One site I visit regularly is a tunnel in the Dumfries and Galloway hills (See "A Most Peculiar Hibernaculum", 28 February 2009). Built several hundred years ago to channel a water supply for a small village, one end is now blocked and the open entrance is less than one square metre. Inside the tunnel opens up to a sufficient height to walk upright and continues through the solid rock for 350 metres (not quite the 500m I said in 2009, but I've measured it now!).

The entrance to the tunnel - about a metre across.

 

Four years ago I was carrying out a survey in the tunnel and found a Daubentons Bat (Myotis daubentonii) that was a bit different from the others: it only had one ear. The other appeared to have been torn off. Perhaps the ear had been lost in a predator attack, or maybe the ear had been caught on a thorn in flight. Whatever the cause, most of the ear was missing, though the tragus (the inner part of the ear appeared to be intact). 

Even more interesting was the fact that this bat was carrying a ring. Unlike birds, which are ringed wholesale, bats are only rarely ringed. This is because it isn't possible to ring bats round the leg in the same ways as birds: their tail membrane extend all the way to the ankles. Instead, bat rings are actually horseshoe-shaped and fit loosely over the forearm. The are difficult to fit and the chances of the bat being later injured by the ring is greater than for birds. For this reason bats are only rung as part of specific research projects, with clearly-defined aims. 

"One-ear" - you can see the ring on her left forearm and her missing right ear.

 

So One-ear's ring number was an important piece of information, but the number extends around the forearm, making it impossible to read without disturbing the bat. I decided to leave the bat and returned four weeks later, fervently hoping it was still there (I didn't want to return more quickly, to minimise disturbance to other bats). This time I was equipped with scales and measuring calipers, so that I could measure the bat's weight and forearm length and make an informed decision as to whether, having been disturbed, it was likely to have sufficient fat reserves to complete hibernation safely (A bat carer was standing by, in case it wasn't). Happily One-ear turned out to be a female and have plenty of fat reserves to see her through the winter.

Armed with the ring number I was able to discover something of her history. She had been rung at a summer maternity roost the previous August by Sue Swift and Iain Mackie of Aberdeen University, as part of a research programme. The roost was 35km away in a straight line, but given the hilly nature of the area it's more likely she had followed valleys to the tunnel, making the journey closer to 45km.

Since then she has turned up in the tunnel as regularly as clockwork every January. Whilst it's nice to see her (and she's starting to feel like and old friend) she is also a useful source of information. Normally I can't identify individual bats within the tunnel but One-ear can be easily identified, allowing me to track some of her decisions about where to hibernate within the tunnel.

Whilst I have seen bats with all sorts of injuries, One-ear is the only one-eared bat I have encountered...until last year, when another bat turned up in the tunnel with a very similar injury, but without a ring. So when I carried out the January NBMP survey this year I had my fingers crossed and I'm happy to report that not only was "One-ear" there again, so was "Lugless"!

It's interesting to conjecture the effect that having a missing outer ear might have on an echolocating bat. It is easy to assume that, with only one fully functional ear  a bat might be unable to gain a three-dimensional image of it's surroundings. The outer part of the ear acts in a similar way to a satellite dish, reflecting sounds into the ear and normally a bat can move the ear to channel sounds from varying directions. However the survival of One-ear and now Lugless shows that they are able to make allowances for this disability and carry on navigating and hunting successfully.

Remember it is a criminal offence  in the UK and Europe to disturb roosting bats without an appropriate license. Bats in hibernation are especially vulnerable. Please don't go poking about underground, looking for bats unless you have been properly trained to do so. Not only are you running the risk of prosecution (quite rightly), your actions may be harmful to bats and underground sites can be very dangerous for the uninitiated. If you'd like to get involved join your local bat group and learn how to do it properly (and legally). 

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A Most Peculiar Hibernaculum

Bats are very good at doing what they shouldn't do: ignoring the books and turning up in the wrong habitat or behaving in an unexpected way. That's part of the charm of working with them. There's a constant chess game in which we try to stay one step ahead.

Usually these unexpected things turn up one at a time and mercifully they are outnumbered by "correct" behaviour. Recently however, I have done some hibernation surveys at a site where the bats seem to specialise in intriguing behaviour.

The site is a tunnel about 500m long, accessed via a small hole, high in the hills of southern Scotland. The tunnel was hewn by hand from the solid rock, in order to carry water from one valley to the next, for industrial use. On end has long since collapsed, but the other is still accessible to those who know where it is. Despite it being far from habitat likely to be used by foraging bats, it seems to be well-known to bats and is regularly used by Daubenton's Bats (Myotis daubentonii) and Natterer's Bats (Myotis nattereri).




The tunnel is small, mostly just high enough for me to stand up in (I'm just over 6 feet tall) and between one and two metres wide. As there are few crevices, the bats tend to tuck themselves into angles in the rock, meaning that it possible to be fairly confident that the majority of bats will be seen during a methodical survey. This is a rare luxury: in many hibernation sites it can usually be assumed that, for every bat seen, there are likely to be more out of sight.




Because of this, I thought it would be interesting to place some temperature dataloggers within the tunnel, to measure the temperature variation at different depths. The dataloggers were in place for four weeks, during which there was a warm spell, followed by several days of very cold weather, accompanied by snowfalls. Despite this, a datalogger just 7m from the entrance (C on the chart) showed a temperature variation of less than one degree either side of 4.5 degrees. A second logger 100m from the entrance (B on the chart) showed a steady temperature of 6 degrees, never varying more than a tenth of a degree. A third logger another 100m in (A on the chart) showed similar consistency around 7 degrees. Hardly surprising then that the tunnel suits the bats well.








Water runs along the floor of tunnel throughout, but never more than a few centimetres deep and I can be quite confident that it rarely rises above that height. Why? because last week I saw a Daubenton's bat tucked into an angle in the rock less than 30cm from the floor. I have rarely seen bats low on the walls of other hibernacula, but here they have been seen doing this several times.

In January this year I walked through the tunnel, noting the various Myotid bats. almost 250m from the entrance was an especially small bat. I had to look at it for a few moments before the evidence of my own eyes registered: it was a Pipistrelle. Why on earth a Pipistrelle had chosen to hibernate so deep in an upland underground site is beyond me! Normally Pipistrelles hibernate in conditions with far less consistent temperature and humidity. I would love to have known which Pipistrelle species it was, but without handling it, it was impossible to tell.


Undoubtedly my favourite oddity at this site was a Natterer's, which had found itself a small crevice. Perhaps the bat would prefer it if the site had more crevices for them to crawl into, as at other hibernacula, because this bat seems to have decided it wanted to be in the crevice come hell or high water. It had managed to get it's head in and no more and there it had settled down to hibernate. It had it's backside stuck in the air and it's wings akimbo, looking for all the world as though someone had hammered it in with a mallet...



Regular reader of this blog will have heard this many times by now, but please be aware that it is usually a criminal offence to enter a bat hibernaculum in the UK without a licence issued by one of the statutory nature conservation organisations (NE, SNH, CCW etc). It is also extremely dangerous to venture underground without training. Blundering about below ground in winter is a great way to harm both yourself and hibernating bats. Sorry, but my sympathies are with the latter! If you want to take part in these activities, join your local bat group. What are you waiting for?

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

Hark the Herald...Moth

Visits to bat hibernacula sometimes produce sightings of other species, which also choose to hibernate in caves and mines. Mosquitoes and bees are occasionally found, but the ever-present companion of the hibernating bat is the Herald Moth (Scoliopteryx libatrix). I don't think I can remember every going into a hibernaculum without also finding Herald Moths: sometimes many dozens, often just one or two.



According to Butterfly Conservation, the organisation charged with conserving our diverse butterflies and moths, there are over 2,500 species of moth in the UK. So why the Herald should be the only one that seems to choose to overwinter in cavses and mines isn't clear. Many species spend the winters as eggs or as pupae, but quite a number apparently do overwinter as adults.

The Herald is a rather attractive animal, with wavy-edged wings coloured with reds and browns, which help it to blend in with dead leaves and avoid predators.

An interesting coincidence is that the Herald is a member of the Noctuidae family of night-flying moths. Something which sets them apart from other moth families is that they have developed a rudimentary hearing organ, which is used to detect the echolocation calls of approaching bats. On hearing an approaching bat the moths wings go into spasm, causing erratic flight, so that the moth is able to evade the bat.

The bats have the last laugh however, in the form of the Long-eared Bats (Plecotus spp.). which have evolved to get by with a very faint echolocation call. Their slow flying speed means that they have less need than other species for advanced warning of obstacles and their phenomenal hearing allows them to listen for prey. Their very faint call (they are known as the Whispering Bat) means that moths aren't able to hear them coming. Thus, a commonly-found sign of Brown Long-eared activity is a pile of discarded moth wings.

It is quite usual to see hibernating bats covered with droplets of condensation. What sparked off this foray into lepidoptery was the discovery today of a Herald in the same state, with huge droplets of water on it's antennae, creating the impression of some kind of miniature bog-eyed monster. Maybe this is the first sign of the moths evolving some form of revenge on the Long-eareds...

For more information on Butterfly Conservation go to http://www.butterfly-conservation.org

Another good source of information on moths: http://ukmoths.org.uk

My website: www.plecotus.co.uk

Hibernating Pipistrelles

Today I spent a very pleasant couple of hours wandering through a semi-ruined castle with members of Lothians Bat group. We were there to look for hibernating bats, which occupy crevices and cracks in the decaying stonework. The most popular spot is in the deep, barrel-vaulted ceilings, which in other old buildings are often used for summer or autumn roosting.


To understand why they are so popular with bats, look at the schematic below. In a typical medieval building, arches and ceilings are built from stone blocks arranged into a curve, so that each is supported by the one outside of it. Above this, the infill is usually made of rubble. Over the years the mortar tends to fall out of the gaps between the stone blocks. As long misguided perfectionists don't repoint the stonework, this creates crevices, some of which may extend into spaces within the rubble fill, creating sometimes quite large bat havens. The downside for us is that surveying these buildings quickly causes a sore neck, from peering upwards, pointing a light into the crevices!


What is particularly interesting about the site we visited today is that, not only is it used by hibernating Brown Long-eared Bats (Plecotus auritus), two of which we saw, it is also used by Pipistrelles (Pipistrellus sp.). Remarkably little is known about the hibernating behaviour of Pipistrelle bats: they are rarely found in the mines and caves where larger British bat species are found hibernating. It is generally assumed that they hibernate individually in small crevices in trees or buildings and are probably more tolerant of fluctutations in temperature and humidity. So it was nice to find at least twelve of them here.

Unfortunately, it isn't possible to say whether they were Soprano Pipistrelles (Pipistrellus pygmaeus) or Common Pipistrelles (Pipistrellus pipistrellus): the physical distinctions are difficult enough with a bat in the hand! However, a braver bat-worker than I might note the dark muzzles and wonder if they might be commons.

Click on the picture below to see a larger version of it and you'll see the brown splodge in the centre resolve into a Pipistrelle's face.

The following two pictures show two groups of bats, sharing crevices. I have no idea how many are hiding behind the mortar in the first picture, but the crevice in the second contained seven bats.

My website: plecotus.co.uk

Lime kilns, mines and souterrains

During the recent spell of unseasonably pleasant weather (back to normal now - there's rain going sideways past my window) I and a bat group colleague spent an interesting afternoon in an upland area of Midlothian, looking at various man-made structures with potential to be either hibernacula or summer roosts.

Information on the sites had come from a mixture of word of mouth and references on the CANMORE archeological database (see Armchair roost-searching, February 2008). Some CANMORE references can be little more than a name and grid reference, others include detailed archeological descriptions, which can be fascinating.

The first site was a limestone mine. This is a known hibernaculum, which has been grilled in the past, partly to protect hibernating bats from disturbance and partly to prevent adventurous youngsters from getting themselves into difficulties. I wanted to take a look, as I hadn't previously seen the site and it apparently used to have an underground link with another site, which Lothians Bat Group survey every winter for hibernating bats.

Hibernaculum grilles have quite widely-spaced, horizontal bars, to prevent human access, but make it easy for bat to fly through. It seemed some local wit had been there before us, and left his thoughts for all to see.

The next plan was to look at several lime-kilns, which are prolific in the limestone areas of Midlothian. These are large stone-built structures, usually built into a hillside. Inside is a tall, brick-lined charging-column, into which limestone and fuel was placed. At the base are draw-holes, usually with a barrel-vaulted roof, which are used to control the air-flow, and to draw the completed lime out, ready to be mixed with water and used as fertiliser or building mortar.

Barrel-vaulting can lose it's mortar over time, creating deep crevices, perfect for hibernating bats. Also, the stonework of the kiln can decay, creating roosting opportunities. Unfortunately, none of the three kilns looked at had many crevices in the draw-holes, but all had decaying stone-work to a greater or lesser extent.

One of the kilns was a massive structure, with two charging columns and six draw-holes, all in excellent condition, making me wonder if it may have been rebuilt in the 1930s, when the government offered incentives to farmers to burn lime, due to concerns about deteriorating land fertility.

At the other end of the scale was a badly-decayed kiln within dense woodland. Landslips had partially buried it and we found a solitary bat dropping in a huge crack in the stonework. A single dropping doesn't make a roost, but it may be worth a return visit in the summer.

The third site had a lovely Barn owl (Tyto alba) roost: a deep hole, high up on the side of the kiln, with long white streaks, left by the owl's characteristic runny droppings. Inside and on the ground below were plenty of large, dark-coloured owl pellets.

There was no sign of the owl (or owls), though it could have been deep inside it's roost-hole, out of sight. Not a bat roost, but it was very nice to see signs of this scarce bird, all the same.

Having seen enough lime kilns to last a while, the last site of the day was a soutterain. These are iron age (about 700BC-500AD) structures, believed to be underground storage facilities. In an age before refridgeration, building a shallow, stone-lined tunnel was a good way to keep food dry and cool, to last through the winter months.

This particular soutterain lies in a small, fenced-off area in the centre of a field. Accessed via a low roofed doorway (and when I say low, I'm talking about crawling on hands and knees), and short entrance tunnel, it is almost 16 metres long and up to 2m wide and high. The walls are made of unmortared stone, full of very deep crevices.

No hibernating bats were visible, but there could have been legions of them, out of sight! With a low, stable temperature and high humidity (yes, it's mud you have to crawl through...), the conditions are ideal for a hibernaculum, especially as it is in area full of excellent bat habitat.

The soutterain is out of sight of the nearest road and probably not known to many people, so is unlikely to suffer much disturbance, especially in winter. That said, a team of Powergen workers, dangling from nearby power lines looked fascinated by what we were up to.

More information about barn owls: barnowltrust.org.uk

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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/

The great hibernaculum search

Ever since we had to cease surveying one of our bat hibernaculum sites because of dangerous subsidence, Lothians Bat group members have been keeping an eye out for other hibernation sites to survey, to add to our two remaining ones.

We have revisited an old limestone mine, last surveyed in the late 1980's, with some success. The January survey there revealed one Natterer's, three Daubenton's, plus an unidentifiable bat's bum poking out of a crevice close to the entrance. It doesn't sound like much, but five bats is a fair result for almost three hours spent underground! (The bat pictured here is a Daubenton's Bat Myotis daubentonii)

Here in Scotland, most hibernating bats are found in old mines or caves, and they tend to be tucked into crevices and holes. For this reason, surveying for them is a slow and laborious business and it's likely that we only see a tiny proportion of the bats present. Nonetheless, it's important work, as we can compare results year-on-year and our findings are fed into the National Bat Monitoring Programme (NBMP).

I have never made any bones about the lack of joy that hibernaculum surveys bring me! The sites we currently visit are fairly civilised, with high roofs and not too much water or clay to wade through, but that's just the luck of the draw! Lulled into a false sense of security I recently agreed to take a small group of intrepid (more so than me) bat-workers to search for a couple of almost-forgotten mines, to see if they could be added to the Bat Group's survey programme.

The first site looked ok at first, though a low roof meant stooping (being 6 feet tall doesn't help!) Most of the floor was covered with about 12 inches of water and one by one we each experienced the joy of rapidly and unexpectedly descending twelve inches as the fine limestone silt undert he water acted like quicksand. Deciding that discretion was a good idea, we retreated and were lucky to leave the site with the same number of wellies we entered with!

The second site was even more entertaining, as recent heavy rain and a build-up of rubbish at the entrance meant that the water was within eighteen inches of the roof. I wasn't too keen on the colour of the water, either.

If you're interested in hibernaculum visits please ensure you work with your local bat group. Not only is it potentially dangerous to do this without appropriate equipment and experience, it requires a bat roost visitor's licence with a specific endorsement. Accidentally disturbing bats during hibernation is very easily done and can have a devastating effect on the bats.

National bat Monitoring Programme: http://www.bats.org.uk/nbmp/index.asp

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