What's in a city?

In modern Britain we live in a man-made landscape. Whether you look at stone walls and sheep folds on a remote hillside in Sutherland, a leafy farmscape in Devon or a built-up part of south east England, man's handiwork is there to be seen, profoundly affecting the habitats available to our wildlife and of course, our bats.

I have always found it interesting to place wildlife within the landscape: where do they live? Where do they forage or hunt? How do they move through the landscape? Where are they present or absent? Where are they threatened by predators and where do they take refuge?

We are fortunate in the 21st century to have easy access to satellite photography free of charge, via websites such as Google Earth and Bing Maps, which allow us to explore this swiftly and with a nice glass of Merlot to hand!

I thought it might be interesting to look at a random square kilometre of a major city and see what habitats useful to bats would be apparent, using one of these websites.

Here is my square kilometre. Two things instantly spring out: this is very obviously a built up area, but there are clearly green places here. Are they just amenity grassland, or more structural habitats which might they offer hunting places for bats. And are they connected, allowing bats to move through the city?

Zooming in makes some of these habitats more apparent. Here, the classic suburban wildlife habitat displays it's strength. These gardens may be individually small, but together they form a block of habitat, with trees and shrubs providing potentially good foraging habitat for generalist species, such as Common Pipistrelle (Pipistrellus pipistrellus) and Soprano Pipistrelle (Pipistrellus pygmaeus). In the south Soprano's tend to have a riparian affinity, but here in Scotland they are more numerous than the Commons and tend to use a wide variety of edge and suburban habitats.

Also in my square kilometre is another classic urban wildlife habitat: a cemetary. I recently carried out some bat surveys close to a large cemetery in East Kilbride and was delighted by the number of Foxes which emerged from it each night, to keep my survey team company. On one memorable evening two of us watched a young Fox edge up to within a few feet, grab a plastic bottle and run to a safe distance with it. Apparently unimpressed it then urinated on the bottle and stalked off!

This cemetery appears to enclose a lot of mature trees. These are likely to harbour plenty of insect prey for bats, especially if some of them are native species. Non-natives tend to be home to generalist invertebrates, but native species are also likely to offer a home to many more native invert species, for whom the tree provides more specialist niches.

Also in the square kilometre is what appears to be a public park, probably offering similar foraging habitat for bats (though not necessarily undisturbed conditions to allow Foxes to successfully breed!) So with a cemetery, a public park and plenty of mature gardens our city bats seem to be quite well-provided with foraging habitat. There are also plenty of houses and industrial buildings which seem likely to provide the potential for roosting Pips and some of the more mature trees could include holes and crevices for roosting bats too. The next question is how do the bats move between all the features? What commuting corridors are available to them?

Often lined with trees and shrubs, urban railways offer excellent wildlife corridors and this square kilometre has several. Here two cross each other and elsewhere a disused railway line has been developed into a cycleway. I'm sorry to revert to a foxy, rather than batty theme, but I was travelling on a train in Ealing which stopped at signals. Right outside the carriage window a vixen relaxed in the sun, whilst her three cubs played, completely unperturbed by the proximity of a trainload of disgruntled commuters!

Even better, within this square kilometre is the mother load: a stretch of canal. With trees, shrubs and hedges providing security for commuting bats and foraging opportunities for Soprano Pips, this is an excellent wildlife corridor. Emergent and submerged vegetation provides homes for plenty of invertebrate prey for Daubenton's Bats (Myotis daubentonii) and the smooth water is perfect for them to hunt over. Smooth water helps echolocating Daubies to pick up emergent insects on or just above the surface.

Canals without vegetation are not necessarily poor foraging places. A few years ago I surveyed the Union Canal with a team of volunteers, attempting to map foraging sites. To my surprise, the most active foraging sites were the ones with little or no vegetation, rather than those with plenty of vegetation and diverse prey species. These concrete-lined canal sections had large numbers of Chironomid midges hatching. They are amongst the first species to occupy stagnant water and the bats demonstrated that, as far as they were concerned, quantity trumped diversity!

The next time you encounter a bat, try using this method to look at the surrounding habitat. You may be surprised how much you can conclude about likely hunting locations, commuting routes and possible roost sites which the bats may use.

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

An Intrepid Batling

Baby animals are amazing things: endowed by nature with astonishing resilience, combined with survival instincts.....

Sadly, when the two bats flew I didn't have the camera to hand and it was over very quickly, so you'll just have to take my word for the last part!

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The Diffusion of Useful Knowledge

Having a first degree in history I have always had an interest in how our understanding of bats has developed down the years (see "An 1892 bat-worker", January 2009). Today's post brought me a copy of "The Penny Magazine of the Society for the diffusion of useful knowledge", published on 7 January 1843.

My first thought was what a wonderful-sounding title and what a sign of the times that there existed a Society for the Diffusion of Useful Knowledge. The Victorian moneyed classes were incredible busy-bodies and loved trying to enhance people's lives, often in rather idiosyncratic ways. (Strangely, paying people enough to live on was rarely considered a way of enhancing lives!)

A regular feature of this paper is a series entitled "Curiosities of British Natural History" and this issue's feature is about bats. Sadly, the author's name is not given but it was either someone who knew the subject or who did a good deal of research as it contains several pages of detailed description of the subject.

Above the start is a gorgeous engraving, showing a Noctule, a Pipistrelle and a Long-eared Bat. The latter has a thoroughly cheesy grin on its face and the Noctule looks too portly to fly, but some of the anatomy is surprisingly detailed: presumably they were engraved from dead specimens.

The article begins with the enticing statement "It may surprise some of our readers to be informed that sixteen or seventeen distinct species of bats are natives of the British Isles". What?! That is our current understanding (depending on whether you include the Greater Mouse-eared or not). In 1843 the two Pipistrelles had not been separated, nor had Brandts and Whiskered Bats. The finding of Nathusius Pipistrelles in Britain was long in the future and, although it had been described elsewhere, I don't think the Grey Long-eared had been discovered in Britain at that time.


So what were the other four species? Unfortunately, the anonymous author doesn't tell us. In fact he only describes eight species, dismissing all the others as "extremely rare and restricted to certain localities". Was he guessing? Was he reading a foreign book and assuming the same species were here? Was he including some long-dismissed sub-species or perhaps bats found in part of the Empire? How frustrating!


The species he describes are: The Common Bat (Pipistrelle); The Great Bat (Noctule); The Long-eared Bat; The Barbastelle; The Reddish-grey Bat (Natterer's); the Whiskered Bat and the Greater and Lesser Horseshoe Bats. The obvious missing species is the Daubenton's, which must surely have been known at that time and would have been relatively easy to distinguish.

As with all writing of the era, wordsmithing was a priority and some of the descriptive text is fantastic: "Often during warm summer evenings have we seen numbers, perhaps several scores, of the Common Bat flitting over pools, in chase of gnats and similar insects, or gambolling with each other in a mazy dance, ever and anon uttering sharp shrill cries of exultation and delight..." The shill calls were presumably social calls, which are sometimes just within the range of human hearing. Incidentally, a score at that time was an innocent number twenty, in case you think the author was using dried bats for questionable purposes.


The piece includes a surprising amount of scientific detail, for example listing the species found to hibernate in caves as Natterer's, Whiskereds, Barbastelles and Long-eareds, though again Daubenton's are conspicuously absent (could it be they confused them with Natterer's at this time?). Given that this was a popular paper, not a scientific journal, there is a remarkable amount of detail: something today's press could learn from.


As with today's press however, the author just can't resist a lurid story and describes bats stealing bacon from chimneys and eating meat in larders. Not perhaps as daft as it sounds, in an era when bacon was hung in chimneys to cure and when meat was kept open in a larder. Houses would have been quite porous to bats at that time and I can imagine a stray Pipistrelle within a house, finding itself next to a joint of raw meat, having a nibble, possibly for the water content.


Something exciting about old texts like this is when they describe the location of bat roosts. The author mentions a Noctule roost under the eaves of Queen's College Cambridge and Greater Horseshoes occupying caves "at Clifton and in Kent's Hole, near Torquay". If anyone reading this lives in those areas, it would be fascinating to know if these sites are still occupied, 166 years later!


At the time this paper was produced, people were still grasping to understand how bats found their way in the dark, and, reading the author's description one gets a sense of his frustration: they knew there was something special about it, but couldn't quite put their finger on it:


"There is a singular property with which the bats is endowed, too remarkable and curious to be passed altogether unnoticed. The wings of these creatures consist, as we have seen, of a delicate and nearly naked membrane of vast amplitude considering the size of the body; but besides this, the nose is in some furnished with a membranous foliation, and in others the external membranous ears are enormously developed. Now these membranous tissues have their sensibility so high, that something like a new sense somehow accrues, as if in aid of that of sight. The modified impressions which the air in quiescence, or in motion, however slight, communicates; the tremulous jar of its currents, its temperature, the indescribable condition of such portions of air as are in contact with different bodies, are all apparently appreciated by the bat." So near, yet so far!


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Alana or Envisage?

For years Alana Ecology have been the benchmark supplier for wildlife survey equipment. They were never the cheapest supplier, but their catalogue always drew together kit from a huge range of manufacturers. It always seemed to include the very best equipment and this was coupled with excellent advice: if you called you always found yourself speaking with someone who actually understood what you needed and knew the best solution.

Not surprisingly, for me and for many other people who work with wildlife, both professionally and as a hobby Alana became the standard supplier for everything: a reliable source of advice and good kit.

Over the past couple of years there seems to have been a disappointing deterioration in the standard of service provided by Alana: late and missing deliveries; failure to keep the customer informed, failure to call back etc. After several instances of this kind of poor service I started looking around to see who else is out there and a colleague told me about Envisage Wildcare. Their catalogue isn't quite as comprehensive as Alana's (and irritatingly, you have to download it, you can't simply view it on the web), but most of the key equipment is there.

When I needed a new endoscope I decided to give Envisage Wildcare a try. I phoned at 4pm and spoke to someone who took my order. Pushing my luck, I asked if it would be possible to have it delivered the next day? "Erm, yes, but the van is arriving so I'll need to put the phone down now and run". That is the kind of service that attracts attention and true enough, next morning the endoscope arrived.

Since then, I have heard about several other examples of this kind of thoughtful, professional service, experienced by others. I do think that we would be best served by two good companies in competition: that way they keep each other up to the mark and keep prices low. Having heard a couple of people say recently that had gone elsewhere, I hope that Alana recognise and address their service. They have great expertise and I certainly haven't written them off.

If I were to send messages to both companies it would be this:
Alana - sort out your service, keep your customers informed about their orders and lose the complacency.
Envisage - keep doing what you're doing, but for heaven's sake set up a proper on-line shop, instead of the irritating pdf download.

Take a look and decide for yourself:
http://www.alanaecology.com/
http://www.envisage-wildcare.co.uk/

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

Noctules, Boxes and dangling bat-workers

During 2007 and 2008 I spent some time on investigating the distribution of Noctules (Nyctalus noctula) in south-east Scotland, a region where the species was traditionally considered scarce and probably beyond it's natural range. I gathered together incidental records from many bat-workers (thanks!), some focussed car surveys and records from commercial bat surveys carried out by a number of consultants, including me.

The result was a clear indication that Noctules are widespread in the Borders and Lothians regions and probably at a greater density than was previously realised. The results were presented in a poster at the B.C.T. Scottish bat Conference in November 2008. If you're interested you can download a copy as a .PDF file here: http://www.plecotus.net/Noctule-poster.pdf (You are free to distribute this information, in the interests of bat conservation, but please attribute it)

One evening in September I was relaxing in the bar at Preston Montford Field Centre, near Shrewsbury during a training course. My phone made one of the irritating noises that mobiles make, to tell me I had received a text from Carol and Nigel, both active members of Lothians Bat Group. They attached a photo, with the tongue-in-cheek message "do you know what this is?!" You're probably ahead of me here - it was a Noctule, of course. To rub my nose in it, they had found it in a bat box at a country park 2 miles from my home. If I hadn't been on the course I would probably have been there when the boxes were checked. Grumpy wasn't the word for my response....

To their credit, Carol and Nigel had found the first ever Noctule in a bat box in Scotland and it resulted in some positive press coverage for bat conservation. Fast forward two weeks when I was checking bat boxes at another country park, also in Midlothian and believe it or not, there was another Noctule. Like Nigel and Carol's this was an adult female, squeezed into a slim bat box. She was a delight to handle: very relaxed, even when I placed her on a log to photograph her, before returning her to her box. She was also kind enough to give up some Spinturnix acuminatus mites (well, I was happy about it, even if my companions were a little taken aback).

To put this in context, these two animals were both found in boxes in a county where I can count previous records of Noctules in flight on my fingers. Was it coincidence (or was it the same bat, with a sense of humour?) or does this tie in with our new knowledge of the spread of Noctules? It was certainly a surprise in an area with many bat box schemes and two decades history of only ever finding Pipistrelles in them. By coincidence, in 2007 and 2008 a small colony of Natterer's Bats were found in a West Lothian bat box, so these Noctules seemed too good to be true.

Stuart Smith, chairman of Lothians Bat Group (and one of the grandees of Scottish bat-work), came up with an unusual plan to respond to these new records by installing some new bat boxes, higher than normal, something he had seen at a Vincent Wildlife Trust site in Dorset. Most bat boxes in the Lothians are between 12 and 20 feet (3.7-6.1m ) above ground. Noctules are tree-roosting bats, with a tendency to roost in tree holes, often high up, so higher boxes makes sense. The problem is that 20 feet is the maximum height for access by ladder, without extra safety measures and skills.

The solution? Suspended bat boxes! We used Schwegler woodcrete bat boxes, suspended from pulleys attached to high branches. Wire rope is used to pull the boxes up to full height -around 40-45 feet above ground (12.3-13.8m) - and tied off on bolts mounted on the tree trunk. These are at ladder height, to prevent the local "yoof" from reaching them. When we need to check and clean the boxes we will simply climb a ladder to normal height, unwind the wire rope from the bolts and lower the box to ground level. Once finished, we simply haul the box back to the top of the tree and tie off the wire rope once more. Ingenious!

Now, there is a chicken and egg problem here: how to get 40 feet up to mount the pulley? The Bat Group is lucky to have access to the services of a professional tree-climber, who also has an affinity for bats. George used his skills to climb the trees and install pulleys for us, making it look easy, as tree climbers always do. However, it's very hard work: you need to combine a high level of physical fitness with some somewhat counter-intuitive skills. Come to think of it, strolling about at the top of a tall tree as about as counter-intuitive as it's possible to be!

Watching a bat-box being hauled 40 feet into the top of a tree was quite exciting. Whether they will attract Noctules remains to be seen...

With work over for the day, George offered a couple of group members the opportunity to try out tree climbing techniques (at very low height) and so, trussed up and roped to the tree, we took our turns at making fools of ourselves. I had tried my hand at this in the past, so probably should have known better, but didn't.

An advantage of this being my blog is that you won't get to see my feeble attempt at tree climbing. However, this seems a good moment to wreak revenge on Carol for last year's Noctule text message. You have to hand it to her: she's enjoying herself, even if she isn't making much progress up the tree!

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

The Anabat PDA Bracket

Last year I described a home-constructed bracket for attaching a PDA over the face of an Anabat SD1 bat detector (Ana...nother thing or two about the SD1, November 28 2008)

Although not as strong as the brackets sold by Titley Electronics, my bracket has the advantage that, if dropped during a survey, the bracket is likely to give way and protect the PDA and its precious data. It also cost roughly a 50th of the price of buying theirs, which is handy in the current economic climate.

Several people have contacted me to ask about the design. It's very simple, virtually "Blue Peter" construction, though without the sticky-backed plastic (I could never put that stuff on without bubbles anyway!)

For anyone who wants to try making one, I have put the details onto a .PDF file, accessible here: http://plecotus.net/Anabat-PDA-bracket.pdf

If you make one please let me know how you get on: mailto:blog@plecotus.co.uk

My website: http://www.blogger.com/www.plecotus.co.uk

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.



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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
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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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Bat-workers & golf carts: be very afraid!

At this time of year there seems little for a bat-worker to do. Hibernaculum surveys are strictly limited, to avoid the risk of disturbance and there are only so many site visits one can do before running out of enthusiasm for assessing bat potential! These are the days when the mind wanders back to highlights of "real" bat work, before the onset of winter.

One such highlight last year was an autumn visit to a well-known golf and country club in the Borders to check and clean the bat boxes. A large group of bat-workers from Lothians and Borders Bat Groups assembled to go round the boxes, checking them for bats and recording the amount of droppings (an indication of how well each box has been used during the year).


I'm not entirely sure whether it shows trust or naivete, but we were allowed the use of a small fleet of golf carts in order to get round the course with our ladders. If you have never seen a conga line of golf carts, full of bat workers and equipment snaking across the landscape you have never known fear!


Fortunately we were accompanied by the course green keeper and one of his team, which probably helped curb the temptation to descend to the level of "Wacky Races". More importantly, it allowed them to see for themselves the great work they have done, making and erecting bat boxes around the course.

Annual bat box checks have several practical purposes. Firstly, the boxes can be cleaned out in readiness for the next year and any damage identified for fixing. Secondly, we have the opportunity to assess the extent to which each box has been used, providing data which shows the progress of the individual bat box scheme and, when combined with other schemes, a rough measure of how bat populations are doing locally. Thirdly and perhaps most importantly, less experienced bat group members get an opportunity to get close to live bats. Many very active bat workers (including me) started off with bats, with the thrill of seeing a Pipistrelle in a bat box.


In South East Scotland it is extremely rare to find anything other than Pipistrelles in bat boxes (with some intriguing exceptions in recent months) and this site was true to that experience. In autumn boxes tend to be used by male Pipistrelles as the base for a mating territory and it is usual to find boxes occupied by either an individual male or by a male and a harem of females. Where boxes are grouped together it is unusual to find more than one occupied, as they would lie within the same territory. The droppings however, often reveal that other boxes have been used, either earlier in the year or in differing conditions, with bats moving between boxes to find optimum temperate conditions.

The course is home to some remarkable buildings and is known to be home to roosts of Brown long-eared Bats (Plecotus auritus), Common Pipistrelles (Pipistrellus pipistrellus) and Soprano Pipistrelles (Pipistrellus pygmaeus). Best of all is a large maternity colony of Daubenton's Bats Myotis daubentonii). Although the roost was breaking up at the time of our visit, we were still able to glimpse a group of around 20 bats clustered together. I took the photograph below earlier in the year, when there were over 50 bats present, with a cluster of Nycteribia kolenatii bat-fly pupae clustered around (you can see them better in the lower picture).


It was a very successful day in terms of finding bats, recording useful data and giving people the chance to get close to bats. Best of all it was that very rare thing: a chance for bat-workers to get together in daylight!

Please note: handling or disturbing bats is a criminal offence without an appropriate licence issued by a statutory nature conservation organisation (Scottish Natural Heritage, Natural England, Countryside Council for Wales, Northern Ireland Environment Agency).

Most bat groups welcome new members and give them the opportunity to take part in events like this. To find your local bat group contact the Bat Conservation Trust

My website: David Dodds Ecology

An 1892 Bat-worker

As an ecologist whose first degree was in history, I have always had an interest in the development of natural history. I would love to have been one of those wealthy edwardian or victorian country parsons whose lives were devoted to natural history (whilst presumably paying a curate to take care of the religious stuff!)

Last year I heard a talk about the use the Botanical Society of the British Isles makes of historical records in order to understand changes in the distribution of vascular plants. Some of their impressive database comes from the notebooks of victorian botanists and the voucher specimens they made, which are often still to be seen in herbaria. Other records are found by trawling old natural history books and drawing out biological records from descriptions of species and their distribution. Inspired by this I resolved to seek out any such data I could regarding bats in my part of Scotland.

It took a while to find a suitable source of data: bats were not recorded anything like as much as vascular plants were, botany being a "suitable" occupation for those few victorians and edwardians who had time to spare. However, I recently came across a copy of "The Mammalian Fauna of the Edinburgh District", written by William Evans in 1892. In it, Evans set out to record the distribution of mammals in Eastern Scotland between the Tay and the Tweed (a rather broad definition of "Edinburgh distict" by today's standards). He particularly wanted to record the distribution of bats and small mammals, as these were felt to be under-recorded at the time. Arguably then, Mr Evans was one of the first ever bat-workers in Scotland.

There are some fascinating distinctions between the work of this dedicated natural historian and modern bat-work, but some remarkable parallels too.

Not surprisingly, the methods used are utterly different and at times seem a little barbaric to a modern reader. In a day when bat detectors were still 6 or 7 decades away, the art of finding bats was focussed on roosts and upon seeing and catching bats in flight. Whereas today we consider it appropriate to make biological records based on seeing (or hearing) a bat and recording the salient characteristics, in an age when conservation was unheard of and probably unnecessary, the true scientist's voucher specimen was a dead animal. Evans described removing bats from roosts, catching them in flight using butterfly and fishing nets, plus some less savoury approaches. The Daubenton's Bat (then Vespertilio daubentoni, now Myotis daubentonii) seems to have come in for more of it's fair share of hasrh treatment: "During the summer of 1869 I observed a number of bats flitting above a still reach of the Esk above Penicuik, and one which I succeeded in striking down with a walking stick proved to be of this species."

Three other specimens of this species were sent to him from the Dunbar area by a contact who, rather than battering them to death with a walking stick, chose the gentlemanly approach....and shot them!

In another section Evans describes how impressed he was with the nimble flight of a Pipistrelle he watched, though his methods of evaluating this were a little rough by today's standards: "In June last I watched one for fully a quarter of an hour flying in the bright sunshine at Broomhall, near Dunfermline and was much struck with its activity and the facility with which it evaded stones and other missiles thrown at it."

Lest you think too poorly of Evans, he also described caring for live bats (probably captures, rather than the sick and injured bats the modern bat-worker might deal with), in particular a Brown Long-eared Bat given to him by the gamekeeper at Dalkeith Country Park (where there is still a Brown Long-eared roost): "It delights in scrambling about the pictures, the window-blinds and even the chairs; and often settles on the floor, where it moves with considerable rapidity (indeed, it may almost be said to run), keeping the body practically clear of the ground. A more knowing little creature I have seldom seen; and, having discovered that there is sufficient space below the room-door for it to creep through, it's endeavours to overcome obstacles placed in the way of it's escape are most persistent and amusing."

Aside from the very limited equipment Evans had available by modern standards, the victorian understanding of bat taxonomy was rather different. He describes there being 12 species of bat nationwide, whereas today we accept there are 16 or 17 (depending on your views about the Greater Mouse-eared bat's status in the British Isles). The most obvious difference is the Pipistrelle. We now know that there are three Pipistrelle species in the UK, whereas in Evan's day only one was known, the splitting of Common and Soprano Pipistrelles being still a century away.

The most surprising thing about Evan's work and the thing for which he deserves to be remembered is the fact that, despite limited taxonomic understanding and huge limitations in method and equipment, compared with today, his description of the bat fauna of the area is remarkably in tune with what we know today. He described Brown Long-eareds as "by no means rare", Daubenton's Bats as "...locally at least, not uncommon" and Pipistrelles as "undoubtedly by far the most abundant and generally distributed." Ignoring the split of the Pipistrelle species, these three are the most abundant bat species in the region today.

More impressive still is that he was remarkably accurate about the rarer species too. He described a record of Natterer's Bats from near Dalkeith (the two known roosts of that species in the Lothians today are in the Dalkeith area) and goes on to hypothesise that Whiskered Bats are likely to be present in the region too. They are, but there are only three modern records of them in the Lothians. In fact, his only shortfall was his failure to mention the Noctule, which we now know to be present in the Lothians. Whether they were present 117 years ago is a moot point, but it's only in the past decade that they have been identified in south east Scotland. Were they here in Evan's time? We'll never know.

If you're interested in helping to put historical biological records to work, try visiting http://herbariaunited.org/atHome/ This project uses on-line volunteers to transfer information from thousands of old herbarium sheets onto a modern database. It's easy to do and rather addictive!

My website: http://www.blogger.com/www.plecotus.co.uk

Biological Recording & The Scottish Parliament

My recent work on Noctule distribution in south east Scotland (when I get a moment I'll write an update on it) clearly showed how disjointed biological recording is at present. Common understanding of the distribution of this species north of the border turned out to be at odds with reality, once an effort was made to gather records from all possible sources and to address shortfalls. It's relatively easy to do this with a charismatic mammal species, but what about the thousands of other species, for whom we have disjointed and poorly collated distribution information?

BRISC (Biological Recording in Scotland) have placed a petition on the Scottish Parliament website, calling for action to be taken to address this, so that planning and conservation decisions can be made on the basis of full and appropriate information.

Please take a moment to sign the petition. it doesn't matter if you're not resident in Scotland - your opinion still counts.

http://epetitions.scottish.parliament.uk/view_petition.asp?PetitionID=291

Thanks

El Duende, Tomb Bats and Handling the Hairy-legged Vampire

With a title like that, perhaps I should have published this at Halloween! But this is the time of year when relatives (or Mr Claus, depending on your age-group) are liable to ask that awful question "What would you like for Christmas?" Having dispensed with the obvious, but hopeless answers of a Jaguar XK120, a Hebridean island and an unlimited research budget (why is it only kids get their heartfelt desires at Christmas?) we then have the nightmare problem of coming up with something we actually want for Christmas that costs under twenty quid. And if we don't come up with something pretty damn fast the result will inevitably be socks, a jumper or one of those naff coffee table wildlife books with lots of pretty pictures and no real content.

Given that last thought, it occurred to me to share my thoughts on three bat books I have come across recently. They are out of the mainstream but they're a good read and are actually in print, unlike some books which should be but aren't (yes, I mean you, Collins New Naturalist - get your fingers out and reprint John Altringham's book.)

The first is the inspiring and impressive "A Bat Man in the Tropics: Chasing El Duende" by Theodore H. Fleming. Fleming has spent his entire adult life studying bats in Central America and Australia. I find it hard to get into books which simply describe impressive wild animals I am unlikely to ever see. Fleming doesn't do that: this is a very readable book which describes his life's work in a very human way. You really feel you're with him, up to your ears in mud and insects, studying pollinating bats. If you want something to immerse yourself in, rather than watch Chitty Chitty Bang Bang on Boxing Day, this is it.

Incidentally, "El Duende" is Spanish for ghost or hobgoblin, which seems quite appropriate, but Fleming uses it as a metaphor for the seach for knowledge about bats, which is deeper but also appropriate.
Next comes a small book called simply "Bats in Roofs". I have to admit I bought this without realising it's provenance. It was published by the Bat Interest Group of Kwazulu-Natal (for those who had the misfortune to be educated instead of going to school, that's in South Africa). This book describes the bat species found in the group's part of Africa, but what fascinates me is the detailed information about bat management techniques used there. They have similar bat-work problems to us in the UK (hence the name of the book), but with interesting twists. For example, the structure of their buildings are very different and their bat species occupy a broader range of niches than ours.

A common problem there is the occupation of verandahs by Epauletted Fruit Bats and Mauritian Tomb Bats (they have great common names for their bats), with the accompanying mess caused by loose droppings. And the solution? A helium balloon tethered on the verandah is apparently an effective deterrent! For anyone involved in practical bat work in the UK, this book offers a new angle on the subject. What is more it's only 44 pages long, so it lies within the pocket of your younger relatives. If they're anything like mine, they'll have found it on-line, ordered it and returned to their Playstations before you've even powered up your laptop.

My final suggestion is "Expedition Field Techniques: Bats". Written by Kate Barlow (now of BCT), this is a practical guide to carrying out field work with bats abroad. It's very comprehensive: for example, I opened it at random and found a picture entitled "Handling a hairy-legged Vampire Bat caught in Columbia". So if you'd like to know how to handle a Hairy-legged Vampire Bat in Columbia, this is the book for you. It is a concisely written manual which is aimed at the professional zoologist and, like the other two books, it throws an intriguing light on the practical study of bat ecology around the world. I find that dipping into it occasionally puts a new angle on British bat work and sometimes puts the difficulties of studying bats in the UK into context.

So, those are my suggestions. If you get a stripey jumper or a pair of furry slippers for Christmas, don't say you weren't warned.

• "A Bat Man in the Tropics: Chasing El Duende" by Theodore H. Fleming is published by the University of California Press (2003)
• "Bats in Roofs" by The Bat Interest Group of Kwazulu-Natal is published by Flame Tree Media (2007)
• "Expedition Field Techniques: Bats" by Kate Barlow is published by the Expedition Advisory Centre of the Royal Georgraphical Society (1999)

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

A Conundrum of Parasites

I was asked to do a talk at the BCT Scottish Bat Conference this year about bat parasites. What follows is a simplified version of my presentation...


When Anne Youngman first asked me to do this presentation I put the phone down and found myself looking at the slides, jars and vials, containing hundreds of specimens of bat parasites, which as you can see take pride of place on my desk. I found myself wondering what the collective noun for a group of parasites might be. You get a herd of cattle, a parliament of owls, a murder of crows and even a boogle of weasels: what about parasites?

My first thought, given the reaction of most people to parasites was a yeeuch of parasites. Then I reflected that that doesn't match my own view: I find these strange creatures quite fascinating. Then I considered an omnibus of parasites, given the number of times I have searched in vain for specimens of a particular species, only to have several come along at once. I finally settled on a conundrum of parasites: there are many gaps in our knowledge and unasnwered questions about the parasites hosted by bats, so conundrum seems an appropriate noun.

What I would like to do today is introduce you to just a few of these conundrums or unaswered questions and hopefully show you how we, as active bat-workers, can make a contribution to answering these condundrums.

First though, for the benefit of those who haven't recently looked at page 54 of "The Bat Worker's Manual", which gives an excellent summary, here's a brief overview of British bat parasites, to put what follows into context.

The basic definition of a parasite is an animal (or plant), which lives on another animal and gains nourishment from the host, without benefitting it or killing it. It is also useful to understand the difference between ectoparasites, which live outside the host's body (e.g. fleas and ticks) and endoparasites, which live within the host's body (e.g. tapeworms or helminths). In this talk I will be concentrating on ectoparasites, and specifically those which are large enough to be found by us when handling live bats.

We should also consider host specificity: some parasites are generalists and may parasitise almost any warm-blooded animal. For example the ticks or hravest mites that pester me are as likely to pester my dog or a passing fox or deer. On the other hand, some parasites are highly host specific and will only parasitise a single species or perhaps a genus or small group of hosts which share a roost. Many bat parasites are highly host specific.

Let's briefly consider parasites taxonomy. British bat ectoparasites fall easily into five convenient groups. The arachnids are closely related to spiders and this is reflected in the fact that adults have 8 legs. These comprise the ticks and mites. Insect parasites of bats comprise fleas, bat bugs and bat flies.

Clockwise from top left - Nycteribia kolenatii (bat fly); Ischnopsyllus octactenus (bat flea); Argas vespertilionis (bat tick); Spinturnix myoti (bat mite). Centre: Cimex lectularius (human bed bug).

These pictures show a Blyborough Tick or Argas vespertilionis, one of just two species of tick wheich exclusively parasitise bats in Britain.

The mites are represented by Spinturnix myoti, one of over 50 mite species recorded on bats in the UK. As well as the largest group they are also the most diverse, occupying many different niches around the body. This species lives exclusively on the wing and tail membranes. This is a female, indicated by the rounded abdomen. This species is viviperous and she is gravid: carrying a larva, to which she will soon give birth as a protonymph. Or that would have happened had she not been pickled in alcohol!

As you can see, bat fleas look superficially like the fleas you may find on your cat or dog: dorsally flattened and with huge legs. Eight flea species have been recorded on bat in Britain.

There are two species of bat fly believed to be present in the UK, usually found on Daubentons and Bechsteins Bats. A third species is believed to be extinct. These animals are highly adapted to life on a bat. Although they are flies, their wings are reduced to simple buds.

Finally, I have shown here a picture of a human bed bug to illustrate the very close similiarities between bed bugs and bat bugs.

A fascinating aspect of this subject for me is the lessons that bat parasites can teach us about their hosts. For example, when sampling mites on Natterer's and Daubenton's Bats in autumn I have often noticed a significantly higher parasite load on females and juveniles than on adult males. This presumably reflects the fact that the females and juveniles have been confined together within the maternity roost for a number of weeks, giving the mites the opportunity to reproduce and spread from host to host. The males on the other hand, will have been in smaller groups and able to move between roost sites much more frequently, reducing the opportunity for the parasites to spread.

With the development of Mitochondrial DNA analysis, there will be many more opportunities to use parasites to learn about bats. A good example is a piece of work recently completed in Switzerland, which studied MtDNA in Greater Mouse-eared Bats, a species of mite which parasitises them and another bat species which also hosts the same parasite. Using their data, the researchers were able to demonstrate that the Greater Mouse-eared, whose distribution is restricted to mainland Europe, was previously present in Corsica.

My first conundrum relates to the Spinturnix family of mites: the Spinturncidae. These are the largest mites found on bats and often the most obvious to the naked eye. They are between 0,5 and 1.5mm long and are only found on the win and tail membranes of the bat, making them easy to see. This slide shows a Daubenton's Bat and you can just make out something within the red circle.

When we zoom in we can clearly see a mite on the wing membrane. This is Spinturnix myoti, a species which parasitises Daubenton's, Natterers and Whiskered Bats.

This brief segment of video shows it's close relative Spinturnix acuminatus. I recently removed this specimen from the wing of a Noctule and here we can see it walking across a microscope slide. You can make out the slightly pointed abdomen, in contrast to the rounded abdomen of the gravid female we saw earlier, indicating that this is a male.

In 2003 Anne Baker of the Natural History Museum and Jenny Craven of Leeds University published a paper which brought together a piece of work funded by the british Ecological Society. They set out to gather all the known records of bat mites in Britain and to examine all available specimens. Their paper set out a checklist of species. This slide summarises their results for the Spinturnix family: eight species, each with the main hosts. However, there are two problems.

Spinturnix Species A has yet to be formally named as a species and may turn out to be a variant of Spinturnix acuminatus. A few female specimens were found on Barbastelles and, until more specimens are founf, the status of these mites will remain uncertain.

Closer to home is the question of Spinturnix mystacinus and Spinturnix myoti. S. myoti is found on Daubenton's, Natterer's and Whiskered Bats. S. mystacinus is found only on Whiskered Bats, the difference between the two being very small. It may be the case that it is in fact a synonym of S. myoti. As you migh expect, a problem with resolving this taxonomic issue is the fact that Whiskered Bats are far from common. More specimens of Spinturnix mites from Whiskered Bats could help in clarifying the status of this species.

Conundrum two concerns the geographic distribution of ectoparasite species. To illustrate this I have chosen to use the Blyborough Tick Argas vespertilionis. This slide shows dorsal and ventral views of an adult. The ruler alongside shows millimetre divisions. I have selected this species because it is easily identified: it is almost entirely round and usually looks like a little 5p coin, either lumbering about the roost as an adult or as a larva, attached to a host, lying vertically within the fur.

The other reason for choosing this species is that it is supported by a professional recording scheme: the Tick Recording Scheme, run by the Health Protection Agency. If any bat parasite species is likely to be well recorded, it is this one.

The main chart here shows the existing distribution records in Scotland: just four records, some of them quite old. Does this indicate that this species is scarce? Or that it is declining, or limited in range to the west?

Probably not: if you look at the inset map, I have added records based on specimens I have found or which have been sent to me over the past two years. As you can see, this has trebled the number of records in Scotland for this species. Bearing in mind that this is probably the best recorded bat parasite species (possibly excluding the fleas, which have a very dedicated national recorder), you can see the problem with distribution data!

Conundrum 3 relates to the so-called Chigger Mites or Trombiculidae. This picture shows the larav of a member of this family. You can make out the mouth-parts to the left, sourrounded by the legs: only six of them as this is a larva. The remainder of it looks pretty much like a little orange jelly-baby.

This slide shows them attached to a host: in this case a Soprano Pipistrelle, with four larvae attached to her ear. They remain attached whilst taking a blood-feed, which provides what they need to metamorphose. After a few days they leave the host and as nymphs and adults they predate on smaller arthropods within the bat roost.

I have seen these larve on Soprano and Common Pipistrelles, Natterer's Bats and Daubenton's Bats. (at this point I asked for a show of hands and over half the audience had also seen Trombiculidae larvae on bats). From that we can see that this is far from an unusual feature.

When Baker and Craven completed their study of British bat mite records in 2003 they had found only four records of Tromiculidae, one of which is questionable. Why should this be? As with the Blyborough Tick, may be partly about a lack of recording effort, but there is another problem with Trombiculidae: identification. There is in fact a published key to thes family. So surely it's just a matter of working through the key until you arrive at the species? The problem is that the key runs to five volumes and the volume which refers to the species found on British bats is 1,100 pages long! So identification of these mites is a real labour of love.

The final conundrum concerns bat bugs. This amazing picture was sent to me recently by Paul Hope and shows a Noctule with two bat bugs attached to it's forearm. My question is: are they Cimex pipistrelli or Cimex dissimilis? There is a long-standing uncertainty about whether both these species are present in the UK or not, fuelled by the fact that the differences are tiny and the taxonomy is the subject of some uncertainty. A DNA study in the Czech Republic aims to resolve these issues and specimens of bat bugs, especially from Pipistrelles, are sought to assist in this.

One of the joys of working with parasites is the occasional opportunity to gross people out. I notice I wasn't scheduled last before lunch, probably for very good reasons...

This slide shows the business end of Cimex pipistrelli. It's a ventral view of the head and I've labelled the forelegs and antenna, to help you get your bearnings. You can just make out the stylet, the organ the bug uses to feed, lying flat against the underside of the head, within it's protective sheath.

This slide shows how the bug uses it's stylet to go about feeding. You'll notice I have coloured the host a fetching pink, to reflect the fact that human bed bugs feed in exactly the same way!

First, the bug pushes it's stylet through the skin of the host...

This is where it gets interesting. The stylet is both flexible and prehensile and it commences probing around the flesh...

...until it finds a capillary and commences feeding. The probing and cutting through the flesh creates a contusion and slight swelling which is occasionally visible on the wing of bat. You may also find it on your own body if your choice of last-minute bargain holiday doesn't wuite work out as you had hoped!

I hope you have found this talk interesting and that one or two of you may still feel like eating your lunch. Hopefully I have also shown what an opportunity there is for us, as active bat workers to make a very real difference to the sum of human knowledge in this area. The four conundrums I have described barely scratch the surface: the simple fact is that any and all parasite specimens are useful and welcome.

(A handout in the delegates pack included details of how to take specimens and where to send them, together with a bibliography - there is more information on this on my website)

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

Ana...nother thing or two about the SD1

Earlier in the year I described my impressions and opinions about the Anabat SD1, describing it as "God's own bat detector" (August 2008). Since then I have had many more opportunities to use the machines in a wide variety of situations and discussed them with a number of people, including those who were kind enough to reply to my post with advice and information (thanks!).

One thing I commented on then was the option to pay nearly £450 extra for a PDA (hand-held computer) mounted on a bracket on the front of an Anabat. This delivers the opportunity to view live sonograms as bats fly past. Although a great teaching tool and potentially quite useful in the field I had strong doubts about whether this was a realistic option as it is a lot of cash to lay out on something which would be vulnerable to damage in the field, unlike the Anabat on it's own, which is quite robust.

After receiving some intriguing emails I decided to look for an alternative way of achieving the same end. I spend quite a bit of time training bat-workers and a way of displaying live sonograms without touting a lap-top around could be very handy.

The finished SD1 + PDA + GPS in use

Chris Corben, who designed the Anabat, has an excellent website, full of practical suggestions, based on his own experience of using Anabats (see below). This includes a step-by-step idiot's guide to setting up a PDA to work with an Anabat and even some advice on PDA models known to work. A look on eBay revealed that some of these are out-dated for more advance puposes and are therefore available cheaply second-hand. A few days later I had an HP Ipaq HX2190 in my hands for the princely sum of £38.25. It came with the cables and cradle to charge it and link it my home PC. Following Chris's notes it was remarkably easy to install Anapocket (the PDA version of the Anabat software - it comes free with the Anabat) onto the PDA and I was quickly able to view sonograms I had recorded previously.

Next I needed to connect the PDA to one of my Anabats. The cable used for this is the same as those used for synchronising a PDA with a PC - I just needed to find one with a serial plug rather than the more usual (nowadays) USB plug. Once again eBay came up trumps (£3.85). Hey presto! Live sonograms - it really was that easy.

The next thing I needed was a bracket to attach the PDA to the Anabat, so I could walk around with it. There are three threaded holes on the SD1 case, designed to take bolts on the standard bracket. These are simply M3 machine screw holes (the bolts are readily available from DIY shops). I considered making a bracket out of some aluminium or brass sheet, with two folds to make the required U shape. I remain concerned about the vulnerability of the whole set-up and decided instead to make a bracket out of 7 mm foam board - a lightweight yet strong material used in building exhibition displays etc and available from large stationers.

A little experimentation showed the best size and shape for three pieces to create the bracket (email me if you'd like a copy of this). A little Araldite and spray paint (the latter more cosmetic than anything else) and I had a strong, yet light bracket. I attached the PDA to the bracket using stick-on velcro strips. In the event of the unit being dropped or bashed against something the foam board is likely to break before the PDA, so my small investment will be safe. More importantly, so will any survey data on the PDA.


To make the most of this new set-up in the field I needed two more things: a spare battery for the PDA and a CF GPS unit to plug into the top of it. It is possible to use a Bluetooth GPS with the PDA (if, like my one it is Bluetooth enabled, though I think most are), but Chris mentions experiencing problems with the GPS and PDA losing contact from time to time. I also think that, when using an automated GPS in the field, there is a danger of the GPS losing the satellites and the user being unaware of it. Having the GPS plugged into the top of the PDA means it will always be held upwards, unshielded and in the best possible position to retain a view of the GPS satellites.


In my earlier piece about Anabats I bemoaned the fact that, when using an Anabat with a GPS, it was necessary to manually cross-reference bat passes against a GPS file to get a grid reference for each bat. Using a PDA with GPS resolves this problem and now all my bat passes are automatically grid referenced by the PDA. I also questionedthe problem of losing night vision by looking at a PDA screen in the dark. Even turning down the PDA brightness to minimum may leave it too bright. I had heard a Titley employee describing keeping the PDA facing away when not looking at it, which seemed rather self-defeating. I have resolved this by changing the colours on the screen, so that the background is black and the sonogram traces and Anapocket menus are the only things in a bright colour.

The PDA screen, with the Anapocket background set to black, to reduce glare.

So now I have a great teaching tool, a really good toy and a solution to the problem of GPS-referencing bat passes. Compared to the £450 it could have cost I actually paid a total of £61.63 (plus a bit for postage and packaging). I still think it's a Heath Robinson approach and vulnerable to damage, but I don't mind that so much when I've saved £387. After several decades of living in Scotland, something seems to have rubbed off....

Chris Corben's Anabat website: http://www.hoarybat.com/


Anabats in the UK are sold by Alana Ecology, who are usually knowledgeable and helpful: http://alanaecology.com

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

A Result of Careless Angling

We often hear about the terrible effects that abandoned fishing line and hooks can have on swans, but it isn't so often we hear how it also affects bats. Hear in Scotland the main form of recreational angling is fly-fishing and a fly designed to be attractive to a trout can have just the same attraction for a bat.


One recent Sunday morning I was hoisted from my slothful lie-in by a call from the Pentland Hills Ranger Service. A member of the public had spotted a bat suspended from a telegraph wire alongside a loch used as a fishery and Victor (one of the Rangers) was hoping I could help. The Pentland Hills are close to my home and half an hour later I was standing beside him, looking at the bat, suspended above our heads. It was showing no signs of life.

The first problem was working out what the set of wires carried, as I had no desire to get mixed up with high voltages. Fortunately the bat was dangling from telephone wires. The next problem was how to reach it, 6 metres above the ground. I had brought a telescoping ladder and we tried lashing this to the side of the Ranger Service Landrover. Not only was climbing it not an experience I would repeat in a hurry (awfully wobbly!), it didn't get me high enough to reach the bat.

Enter the owner of the fishery, stage left, with a knife lashed to the end of a long pole (which shows how often this particular problem occurs) With a bit of work the bat was cut free and fortunately had a soft landing. It was a juvenile male Soprano Pipistrelle (Pipistrellus pygmaeus), tangled up in a length of fishing line with two hooked flies. It seemed barely alive, though that may have been partly due to the amount of line tangled round it.

It transpired that the bat had a fly caught in it's mouth, presumably because it had seen what looked like a tasty meal swaying in the wind and attempted to catch it. In the warmth of the vistor centre it started to move about more. I couldn't see the tip of the hook and, as it was quite deep in his mouth, I couldn't be sure if it was caught in his throat. Luckily he was able to drink and later, at home took some minced up cat food (sorry Haggis, but the bat's need was greater than yours!), suggesting he wasn't too badly hooked.

The next morning I contacted the Dick Vet Small Animal Hospital, part of Edinburgh University. Kevin Eatwell, one of the specialist wildlife vets there anesthetised the bat and removed the hook. He seemed none the worse for wear and that evening I took him back to a spot close to where he was found and released him.

On the 300m length of telegraph wire which runs parallel to the loch I could see seven other lengths of fishing line caught around the wire, at least one of which carried a hook. Not only is this the result of bad casting, leaving it without bothering to tell anyone is nothing short of criminal, especially as the fishery owner is equipped to remove it. After all, there has been considerable publicity about the dangers posed to wildife by abandoned fishing tackle causes.

My web-site: plecotus.co.uk

The Dick Vet Small Animal Hospital: http://www.vet.ed.ac.uk/cliniclaserv/HfSA/Exoticwildlife.htm

The Pentland Hills Ranger Service: http://www.edinburgh.gov.uk/phrp/rangerservice/rangerservice.html

Last Bat of Morning

I came across this wonderful piece of writing by Verlyn Klinkenborg, originally published in the New York Times. It really captures the essence of dawn and dusk outside a bat roost.

It's 6 a.m., a dark, gray morning in late August, the dim light a reminder how far we've gone on the downhill side of summer. Ethel, a border terrier, and I are behind the house investigating a woodchuck scent. There is a dark smudge in the mist above us, and then another. The bats are returning to their bat house, a thin, slatted box, high up under the eaves. Each bat comes in over the roof, makes a dive for the ground and then swoops upward toward the narrow entrance of the bat house. Some slip inside on the first try, some fall back and try again. After a few minutes, the air is still, the last bat home. Ethel and I turn toward breakfast.

I have seen the bats come out at evening again and again. It is one of the joys of living here, watching them drop one by one into the night. But I've only seen them coming home a few times. The bats of evening are the last flutter in a world that is growing still. The bats of early morning have already been engulfed by birdsong, rooster-crow, the stirring of nearly every creature on this place. Their flight is less erratic just before roosting, no longer distracted by an insect in the air. It's as though each bat brings a scrap of night's darkness home with it, leaving the sky pale and brightening. It's as though night itself were being stored in the bat house till dusk.

When the last bat had vanished, I felt almost absurdly alone, strangely vacant in that thin slice of morning. It reminded me of a feeling from the city a long time ago - that moment, after staying up all night, when you can feel the world gathering pace and energy just as you're beginning to fade. Watching those dawn bats, I imagined them punching out of their night's work as they settled, and I felt as if I'd somehow clocked into their schedule. And it seemed that the best use of a dark, gray morning with mist in the air was to go back to bed, only a few feet, and a couple of walls, away from where the bats are sleeping.

(Normally I have a thing about horrible US English spelling, but writing this good deserves to be left as the author intended!)

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

Your comments: mailto:blog@plecotus.co.uk

God's Own Bat Detector

Ok, that's maybe overdoing it a bit, but I have recently become a fan of the Anabat SD1. For some time now the SD1, and it's more cumbersome predecessor the Anabat II (with ZCAIM recorder) has been the industry standard equipment world-wide for passive monitoring, and rightly too, but having spoken to several people who rated it highly as a detector for use on transect surveys I though I'd better try it out.

There are several reasons the Anabat is so good for passive recording. Alternative methods of recording bat calls use audio formats such as .WAV or .MP3, which quickly gobble up available memory in just a few hours. The Anabat records each bat pass as a series of co-ordinates, plotting the loudest frequency every few milliseconds, creating miniscule data files, allowing many thousands of bat passes to be squeezed onto a single 1Gb CF memory card.

The fact that the memory card is held within the detector is a further advantage, but the biggest advantage lies in the way the detector ignores the spaces between bat passes and simply records each bat pass (or other ultrasonic noise) as a new file. The Analook software which comes with the machine allows you to very quickly scroll from bat call to bat call, identifying each pass and creating a spreasheet showing each one, with date, time and species. The time saving, compared with using other software analysis systems, such as Batsound or Batscan is huge.

So the Anabat is great as a passive detector - why is it good for transect work? The designer, Chris Corben, has built in an interface which allows a GPS receiver to be plugged into the detector. Every two seconds the Anabat asks the GPS where it is and records that data on the CF card, alongside all the bat passes it records as you walk along. This means that for each bat you encounter you have a sonogram of it's call, the date, the time and an accurate grid reference.

Anabat SD1 with Etrex GPS velcroed to it and connected.

What more could you ask for?

Well, I've made it sound great, and it is, but there are plenty of problems too (though apparently Titley Electronics, who make the machine have recognised that there is a huge market for the machine and are working hard at improving it):

1. The GPS data isn't attached to the sonogram: you have to transfer it manually.
2. Even with the GPS and Anabat both set to the correct time, an error of one hour creeps in, though it's easily edited out.
3. Becasue the machine is built in Australia, the GPS data is recorded as Latitude and Longitude, using the WGS84 datum, instead of the British OS datum. This means you have to use a utility programme to convert the data to British National Grid and remember to convert the datum, otherwise you can end up with proper-looking grid references, which are simply wrong.
4. The standard Anabat microphone is not as sensitive as it could be. I set the Anabat's sensitivity control as high as it could take and used it alongside a Bat Box Duet. The Duet was clearly more sensitive, which was disappointing, given the Anabat's £1,400 price tag.


Despite all the above, Anabat plus GPS is still streets ahead of anything else currently available. When used together with the GPSU GPS utility programme and the superlative DMAPW mapping programme, bat data can be identified and transferred to a map with incredible ease and efficiency. Unlike Victor wotsit, the chap who was so impressed with a shaver he bought the company, I didn't go that far, but three weeks after buying an Anabat for passive monitoring I'd bought another for transect surveys, despite the high price.

It's worth mentioning that you can buy an SD1 with a PDA mounted on the front and a GPS plugged into the hand-held computer. This allows you to see sonograms live and also tags the GPS data onto each bat pass as it records it, which is a fabulous toy, but of questionable value.

I was on the receiving end of a hard sell for this system at the Welsh Bat Conference and failed to understand why I would want to pay an extra £400+ for this. Titley admit that the PDA screen will cause you to lose your night vision and advise that you should carry it, pointed away from your eyes! The bracket looks utterly Heath Robinson and vulnerable. When I pointed this out I was told that the bit which would break if you tripped whilst carrying it would be the bracket, the cheapest part...at £100!

In fairness to Titley and to Chris Corben, this is an excellent idea and has immense potential. Why plug your bat survey data into a computer when you can take the computer to the bats, but there's a lot of work to be done yet. Meanwhile, like many others, I am waiting with baited breath for the new Batbox Griffin to be launched. It just might beat Anabat at their own game.

Chris Corben's Anabat website: http://www.hoarybat.com/
Batbox, makers of the new Griffin: http://www.batbox.com/
GPS Utility: http://www.gpsu.co.uk/
Alan Morton's DMAP mapping programme: http://www.dmap.co.uk/

And of course, my website: http://www.plecotus.co.uk/

Happy Harp Trapping!

A couple of times this year I have described my Tuttle (or harp) trap, built with the intention of creating an effective trap for harmlessly catching live bats, but smaller and more versatile than the commercially-available traps. Cheaper too! (see The Kitchen Table Harp Trap, February 2008).

Back in May I described the trap's first outing, when it was unfortunately placed over a roost entrance which wasn't in use. (See A Bat in the Hand, May 2008). As the bat maternity season started soon after that I had to wait with gritted teeth for the breeding season to end, so I could find out whether the trap worked or not.

A couple of weeks ago Lothians Bat Group had a trip to a site in the Borders and I set the harp trap up at the entrance to a Daubenton's Bat (Myotis daubentonii) roost and waited with baited breath. With 8 or 10 people waiting to get a close-up view of the bats, I couldn't help dwelling on the fact that the wretched gadget had yet to catch a bat - talk about pressure!

The first 2 or 3 bats flew past the trap, finding ways around it or even through it, causing a sweaty brow on my part. However, this is always a problem with harp trapping at a roost, so after a little work closing the gaps with coats, twigs and anything else that came to hand my fingers were re-crossed.

I got involved in a conversation and missed seeing the first bat to be caught, but yes, a bat was actually caught. My week's hard work back in the winter wasn't in vain after all! It quickly became apparent that the plastic lining of the catching bag was too long, which slowed the bat in moving into the sides of the bag, where it could not get out. In all, twelve Daubies were caught and I was able to check several of them for parasites, watched by some Group members. At the same time, other members of the Group were able to gain some valuable bat handling training.

The trap in place at the Natterer's roost (the roost is in a crevice in the wall behind)

Now that I knew the bat worked I followed up with an evening at a newly-discovered Natterer's Bat (Myotis nattereri) roost in the wall of an old farm steading, where I needed to confirm how the roost was being used. Again, the trap did it's thing and I was able to catch five bats (although a sixth was caught as I was taking the trap down). With three adult females, a juvenile male and a juvenile female, I was able to conclude that this had been a maternity colony, with the young bats now flying and the trap had earned it's place.

A juvenile Natterer's Bat

Before I next use the trap I'll trim back the plastic lining. The only other problem that has come to light is that the legs are a bit spindly and wobbly. The trap is light in weight, so the legs don't need to be too strong, so I'll delay making any changes to that for now. But at last, eight months after building it, I know the trap is fully functional and effective.

Please note, everything described above was carried out under appropriate S.N.H. licences. Trapping and handling bats can be harmful to them if not done with the correct equipment and skills. To do so without a licence is a criminal offence.

My website: http://www.blogger.com/www.plecotus.co.uk

Bat Bugs and Bed Bugs

I thought I would take the opportunity to share some pictures of a little friend of mine, with a little friend of her own. She's a non-breeding female Soprano Pipistrelle (Pipistrellus pygmaeus), with a low body-weight and in fairly poor condition. When this photo was taken I had just hand-netted her as she emerged from a roost. You can just make out a reddish blob on her wing, which caught my interest. It's a species of bat bug which is widespread in the British Isles, Cimex pipistrelli.

Bat bugs are interesting creatures: members of the family Cimicidae, which also includes human bed bugs, amongst other delightful creatures. The odd thing about this one is it's presence on a bat in flight. They are temporary parasites and are normally found in cracks and crevices in the roost of the host species. They are not equipped to stay attached to a bat in flight and usually leave the host's body as soon as they finish feeding. I can only assume that this one got caught out!

Like all true bugs (bat bugs are Hemiptera, the same order as such familiar sucking insects as Shield Bugs), bat bugs suck their food via tubular mouth-parts. They use this structure, correctly called a rostrum, by inserting it into their host like a hypodermic needle to ingest body fluids. The close-up below shows the rostrum at rest, lying in a groove below the head and prothorax.

It's interesting to note that human bed bugs are thought to be descended from bat bugs, from the days when bats and humans were more closely associated than today. I can imagine Bronze Age or Neolithic people living in huts, with perhaps Brown Long-eared Bats roosting in the rafters and bat bugs gradually adapting to this larger and less difficult host.


If the pictures haven't given you the creeps, then this will: it's an article from the Lancet, which describes a house in Scotland, where a student was being bitten by what were initially thought to be human bed bugs. They turned out to be bat bugs, wandering from a roost above his bedroom. Fortunately for bat conservation, this seems to have been an isolated situation! http://www.morgellons-uk.net/pdf/bats.pdf


My website: http://www.blogger.com/www.plecotus.co.uk

Peat Bogs, Rape Fields & Other Nasty Places at Night

I've just returned from a week-long soiree in the northern half of Scotland. Not a holiday, I'm sorry to say, but a surveying trip, working at some wind-farm sites.

Surveying wind farms is different from most bat survey work, for two reasons. Firstly, the focus is on finding commuting and foraging bats in the vicinity of proposed turbines, rather than the usual roost-finding focus of most commercial surveys. Secondly, proposed wind farms tend to be in places where no sane bat might be expected to go: exposed, windy places and bats don't usually go together.

The difficulty faced by developers (and their consultant ecologists) is that we don't know enough about how bats commute and migrate around the UK. We know that much migration takes place in continental climates, such as in mainland Europe and North America. We also know that in these places badly sited wind farms can kill many bats. So, until we understand what our own bats in the UK are doing, we do intensive surveys of wind farm sites.

Thus I came to be trekking around various nasty places in the middle of the night, carrying out 5 minute activity surveys at 100m intervals, along transects which took 4 or 5 hours to complete. Fair enough, but when the first site was a called ***** Moss I realised things could get interesting. First came the midges - hordes of the little swine, but I was ready for them with my midge hood. I amused myself squirting them with Jungle Formula and watching them zoom back for second helpings, fangs dripping with my blood (it doesn't matter how much anti-midge gear you wear - they always find a way through).

The next piece of fun was the gradual fading out of the track I was following across the site. Having got lost twice in the dark and had to GPS may way back to a known point on the transect, my sense of humour was beginning to fail me. A quick look at the site plan revealed I needed to follow a fence line for the next part of the transect. I'm not entirely sure why the soggy peat that surrounded that fence didn't suck it down, but it made up for it with me. I consider myself a patient man, but I do recall howling into the wind, as I pulled myself out of my third bog hole, holding the precious Anabat over my head "Wind farm? As far as I'm concerned, they can TARMAC the bas***ding place !!!!".

The next site seemed more civilised, at least from a survey point of view, if not an ecological one. A prairie-sized arable farm, with hardly a hedgerow to be seen and every crop planted close up to the field boundaries. It looked easy enough to traverse, until I met the delights of mature Oilseed Rape. This stuff stood higher than me, stank like Satan's bottom and did it's best to trip me up with it's stout stems as I tried to navigate the eighteen-inch gap between the crop and the barbed-wire fence. But the real problem was the Cleavers. You know, Cleavers, Galium aparine a.k.a. Sticky-weed, Goose Grass etc? Harmless, amiable stuff? Not when it grows in great swathes, fed with nitrogen by the Rape. It grew taller than me, with stems as thick as my little finger, twisting round itself to create a miniature jungle of impenetrability, constantly tripping me up in the dark as I tried to force a way through.

A bat surveyor's lot is not a happy one etc. etc.

Oh, and bats? Surprise, surprise, there were very few and mostly in the obvious places round the edges of the sites.

I said "mostly" and what was interesting was that both sites produced snippets of bat behaviour that went against the books and perhaps justifies some of the survey effort expended at these sites. First, I watched a Common Pipistrelle (Pipistrellus pipistrellus) patrolling up and down a track, feeding on midges. The odd thing was this track was in the middle of a wind-swept moss, without hedgerow, fence or any kind of above-ground feature.

The second interesting thing was a small colony of Common Pipistrelles dispersing from their roost across arable land. Some were following field boundaries, as you might expect, one followed the route of a former field boundary (working from memory?) and I watched another set a course across open arable fields.

We still have a lot to learn about these animals...

My website: www.plecotus.co.uk

Swarming Pipistrelle Video

A few weeks ago I included a brief snippet of video, showing a colony of Soprano Pipistrelles (Pipistrellus pygmaeus) swarming at dawn, before entering their roost. I have now had opportunity to film a longer video with a larger colony.

The video was recorded between about 04.10 and 05.00 on a morning when dawn was around 04.30. A colony count the evening before showed that 383 bats left the roost. I hand-netted two of them and both were lactating females, indicating that this is a maternity colony. When I filmed them it was too early in the maternity season for the young to be flying, but in just a few weeks there will probably be double this number of bats, as each young bat starts to follow it's mother out to feed at night.

The video shows up to fifty bats at a time swarming and there are close-ups of one of the roost entrances, showing how the bats "touch and go" at the entrance, without actually entering. At times, so many bats were attempting to do so that there was an aerial queue and the clattering on the wooden barge-board as they touched and pushed off again was audible some distance away.

Enjoy!

My web-site www.plecotus.co.uk

Welsh Bats and Scottish Bat-workers

Last weekend I made the long trek to Aberystwyth - a 7 hour drive each way - for the B.C.T. Welsh Bat Conference. Organised by Tom McOwat and hosted by Aberystwyth University, this was an excellent conference at a reasonable charge (even for us consultants, who usually pay extra). A pleasant surprise was the discovery that no less than nine of us were travelling down from Scotland, so with a bit of hectic organisation everyone squeezed into two cars and we did our small bit to save the planet and avoid having to remortgage the house to buy a tank of petrol.

There were a number of good talks. It would be remiss of me not to mention the two Scots: John Haddow describing tips for identifying bats in the hand and Kirsty Park on bats in man-made habitats.

Another highlight for me was Helen Miller describing BCT's new survey programme for the rare Bechstein's bat. This rare woodland bat is extremely hard to survey for: they fly fast and cover large distances, so the survey method employs an actic technique: using ultrasonic lures to attract Bechsteins into harp traps by broadcasting their social calls. Very clever, and with a strict methodology that minimises disruption to the bats.

Another fascinating talk was by Chris Corben, the innovative Australian who designed the Anabat system, which is revolutionising professional bat-work. The Anabat SD1 is a frequency division detector which saves data direct to a CF memory card. It allows effective long-term monitoring of bats and is increasingly finding a place in transect work too. With the associated Analook software, which is designed to work with frequency division data (unlike Batsound etc, which use audio files) it is astonishingly easy to analyse large numbers of bat passes swiftly and efficiently.

A very clever idea incorporated into the conference was the usual evening bat-walk. Except it wasn't the usual one. Instead, all the delegates were divided into teams and spread out over twelve woodland sites around Ceredigion. The result: a far greater survey effort in one night than most bat groups could manage in a year. And to validate the results, the Sunday morning session comprised analysis workshops for the various software programmes.

Naturally, the Scottish bat hooligan squad had to push things to the limit. Not satisified with six bat species in our patch of woodland (including a possible Nathusius' Pipistrelle - a very rare species), we wanted more. We set out to look for Lesser Horseshoes, which we were told had been recorded at a road widening scheme a few miles from Aberystwyth. Imagine the scene: a car bursting with wild bat enthusiasts and literally bristling with bat detectors, careering down a Welsh country road in the middle of the night. We had three Bat-box Duets poking out of the sun-roof (set to 20, 50 and 120 kHz), an Anabat SD1 poking out of the side window and one intrepid bat-worker (who shall remain nameless) hunched in the passenger seat, monitoring the frequency division output of one of the Duets, just in case a bat escaped all the other detectors.

So, did we get any Horseshoes? Did we heck. But at least we have an excuse to go back to Wales...if they'll have us!

My website: www.plecotus.co.uk

More on the Bechstein's Project: http://www.bats.org.uk/pages/bechsteins_bat_project.html

Chris Corben and Anabat: www.hoarybat.com

A Rant About Planning

Early in 2007 the Scottish Government (or was it still the Scottish Executive then?) wrote to all local authorities in Scotland, clearly setting out their responsibilities in relation to European Protected Species (which include all UK bat species) and the planning process. What they said includes some very simple guidance: "...it is clearly essential that planning permission is not granted without the planning authority having satisfied itself that the proposed development either will not impact adversely on any European protected species on the site or that, in its opinion, all three tests necessary for the eventual grant of a Regulation 44 licence are likely to be satisfied." Surely that isn't hard to understand?

Why then, are some local authorities still granting planning permission for developments without giving the slightest consideration to protected species? Edinburgh are the worst offenders I know of, but I'm sure there are others. I have recently seen a development involving the direct destruction of a known roost. I was called in by the owner to give advice on how to proceed and was appalled to discover that planning permission had already been granted.

On the other hand, some local authorities are diligent: the planners at Scottish Borders Council not only make it clear to applicants what species need to be surveyed for, they provide succinct guidance, written by the county ecologist and clearly focused on the individual development.

This process is the safety net through which pointless destruction of bat roosts can be prevented: ensuring developers and others face their responsibilities towards protected species and helping them understand what they need to do and when. It's basic and essential conservation law.

My other frustration is the local authorities who approach their Habitats Directive responsibilities with a "one size fits all" approach. One west of Scotland local authority responds to planning applications by setting out what programme of surveys must be carried out, without knowledge of the characteristics of the site or it's bat potential. Yet the BCT Bat Survey Guidelines are clear: "It is worth noting that the type of survey to be undertaken and amount of effort expended can often only be fully determined after visiting the site at least once." I recently completed a pointless set of sunset surveys at a modern city centre building with very low bat potential, no nearby or connected habitat and no records of bat activity in the area. The local authority's ecologist insisted on his standard litany of "two to three emergence surveys", with no mention of an initial inspection survey. After I carried one out it was abundantly clear that no further survey was necessary, but was obliged to do so anyway. As a result, the developers have been delayed, have paid over the odds and are disillusioned with the whole process. In other words, conservation has been discredited by thoughtless actions.

For all I know, their next development could be a steading conversion surrounded by prime habitat: a building with high bat potential. After their bad experience at this site, they could be tempted to turn a blind eye to protected species. If the local authority is one of those which does the same, the result could easily be the destruction of an ecologically sensitive roost.

Rant over (climbs down from soapbox).

Pipistrelle Roosts: from Intermediate to Maternity

The roosting cycle of the commoner UK bat species is reasonably well understood: hibernaculum in winter, then move to an intermediate roost in spring. In the breeding season, the females move into maternity roosts and in most species the males use other sites. Once the young are flying in late summer, intermediate roosts become important again, with mating roosts used in some species, then it's back to hibernacula. More often than not, we only see little snippets of this and have to work hard to interpret what we see. I've been lucky enough to see a slightly bigger piece of the picture with two Soprano Pipistrelle (Pipistrellus pygmaeus) roosts I've been working with recently.

The first is the site at which I videoed swarming bats in May ("Dawn Swarming", 15 May). On that occasion I saw around 70 bats swarming, 30 of which entered the roost, the remainder flying off to the north-east. We know of another roost about 500m away in that direction, so clearly there was likey to be a link. Last week I returned at sunset to do a colony count and volunteers from Lothians Bat Group went to the other roost site to the same thing simultaneously. 48 bats had been counted at the other site a week previously, so I was intrigued to see which roost would be used for breeding.

Unexpectedly, only three bats emerged from "my" roost. I hand-netted one of them, which turned out to be a very small non-breeding female. She was in poor condition and was carrying an enormous (by Pipistrelle standards) Cimex bat-bug (a close relative of the human bed bug) on one wing and huge numbers of Macronyssidae (a family of tiny mites).

Incidentally, it's quite unusual to see a bat-bug attached to a bat outside of the roost. They are not really equipped to grip on to a rapidly moving wing for long and normally feed from bats within the roost, dropping off before the bats emerge, so it looks like this one got caught out! It's probably Cimex pipistrelli, but there are records of another, rarer Cimex species on bats and I'll reserve judgment until I have it under the microscope.

Here you can clearly see the Bat-bug (Cimex sp.) on the bat's wing

And the other site? Only thirty bats emerged, suggesting that the maternity roost is probably somewhere else entirely. What we now need is someone mad enough to prowl the streets of Edinburgh at dawn for a few days, looking for a swarm of bats, to tell us where the maternity roost is! It's not that we really need to know, but it would be nice to find the missing jigsaw piece.

The other site is the one I mentioned in February ("Two Roosts for the Price of One", 6 February), with droppings of two species in the attics. As yet the Brown Long-eareds (if my dropping analysis is correct) haven't put in an appearance. At dawn one morning in May, I watched 7-10 Soprano Pipistrelles swarming around the gable end of the "wrong roof", i.e. the attic which did not have Pipistrelle droppings in it in February. Did I have it all wrong? Was the maternity roost actually here?

(Above) The roost entrance identified in May - the bats swarmed in front of this gable end and entered via the gap visible below one of the roof tiles

(Below) Droppings stuck to the timber facing below it, 3 weeks later

When I returned with a team of helpers at sunset last week, there were many droppings stuck to the wall around the access hole the bats had been using on the previous visit, indicating it had seen some use. However, at sunset no bats emerged from there. Instead, 118 bats emerged from two holes in the gable end of the main attic, right where I originally found piles of droppings within the attic. So, not only were we able to confirm the location of the maternity roost, the May visit enabled the identification of an intermediate roost, which wasn't apparent from signs within the attic.

Bats are always enigmatic and rarely give up their secrets easily. It's nice when, once in a while, we can see tiny bit more of their lives than the usual tiny snap-shots...

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

Ten Things Every Duet Owner Should Know

Last night I was surveying for emerging bats that didn't emerge, so I had plenty of time to think about life, the bats and everything. It occurred to me that the detector I was using, a Bat Box Duet is of the most popular detectors on the market, and rightly so. It's sensitive, selective, ergonomic, robust and sensibly priced.

As with any piece of equipment, there are hints and tips that help the user, some of which I've picked up from other users and some I've worked out myself. So here are my ten top tips for using a Bat Box Duet:

1. Try plugging your headphones into the tape socket, instead of the headphones socket. You will hear the heterodyne detector in your right ear and the frequency division one in your left. Whatever frequency the detector is set to, you will still be aware of bats on other frequencies. The audio level is fixed, so the volume control has no effect: if you're beside a road or river you may struggle to hear over the background noise.

2. If you want to try this technique somewhere where there is some background noise, try plugging the detector into a minidisc machine and plugging your headphones into the minidisc. You should hear the audio from the bat detector and the minidisc volume control will allow you to hear it louder. This is good practice when recording, as it allows you to be confident that the detector output is being recorded properly. It's very frustrating to get to the end of a survey and find you've recorded nothing because you accidentally knocked the stop button or a plug has come out.

3. When the low battery BAT warning appears on the display, don't panic if you haven't brought a spare battery: the detector will continue to function for a short while. Eventually the frequency indication will go haywire and then the detector will switch off the display to save power, but the detector will still operate for a little while longer.

4. Even in that situation you can by without the frequency display. Although you don't know what frequency you're tuned to, if you rub your fingers together, this sound will be loudest at 40kHz, giving you a very rough frequency indication. Of course, its a lot easier just to carry a spare battery!

5. Have you ever wondered why a seemingly random digit appears when you first switch the detector on? This is the software version.

6. If you have a childish sense of humour (like me) you can convince gullible people you have a very clever detector. Using a worn battery, turn the volume high, without headphones. The loudspeaker is the most power-hungry part of the detector so, when a bat is picked up, the extra current consumption will cause the word BAT to appear. When the call ends, the word disappears again. Fun for all the family!

7. Fed up tuning up and down, to ensure you don't miss any bats? Try tuning to 42kHz. You'll hear Myotis calls as a regular machine-gun type call, Common Pipistrelles as an irregular, thudding and Sopranos as an irregular squeaky sound. Noctules can be hear when close, as this frequency is close to the first harmonic of their call. For heaven's sake don't try this for anything important: you will lose a lot of sensitivity, and you may miss something important (especially Horseshoe bats) but it's handy if you just want a general idea of what's happening. I sometimes do this when I set up a Duet on a tripod to record the frequency division output. In that situation I know everything is being safely recorded, so missing the odd call is less important.

8. Did you know there have been some subtle changes in the design of the Duet since it first came out? Earlier versions had a less sensitive microphone, which looks like a small black plastic grille. the later, more sensitive microphone looks like a tiny metal disc, surrounded by a rubber grommet.

9. Another change is the function of the REF button. In earlier versions this produced a steady reference tone. With more recent Duets, this button shunts the microphone to normal audio. This is handy for taking field notes, as anything you say into the detector will be picked up on the left-hand stereo track and recorded (assuming you are recording the survey). Be sparing in it's use: whilst you are talking the frequency division detector is inactive.

10. I only had nine things, so for number ten I'll mention that the Bat Box III has now been revamped into the same style of case as the Duet. I have yet to get my hands on one, but I suspect it will be a very good heterodyne detector. The original Bat Box III was excellent, but it's only weaknesses were poor ergonomics and difficult frequency indication. The new version (Bat Box IIID) fixes both of those issues and will probably be a really good little brother for the Duet.

The Stag Electronics (Bat-box) website: http://www.batbox.com/

My website: plecotus.co.uk

A Bat in the Hand....

...takes a great deal of work to achieve!

In company with a small group of people from Lothians and Scottish Borders bat groups I attempted to try out my new harp trap last night (see "The Kitchen Table Harp Trap", under February 2008).

The site was a ruined castle, set in a secluded valley in the Scottish Borders. "Ruin" is probably the wrong word, as the seventeenth century noble who set about building it never completed the job but, with massive stone walls up to 50 feet high, it really looks the part. Barrel-vaulted cellars with plenty of deep gaps and cracks in the stonework provide good roosting opportunities for bats. There are woods and a river close at hand, providing foraging opportunities for several bat speices and in the past we have trapped Natterer's Bats (Plecotus nattereri), Daubenton's (Myotis daubentonii) and Brown Long-eareds (Plecotus auritus).

Trapping bats is enjoyable, but there needs to be a valid scientific reason to interrupt the bats in their normal activity. On this occasion bats were to be rung as part of a long-running study of bats using sites of this type in the Scottish Borders. In addition, I was planning to remove parasite specimens as part of my studies into their distribution and host associations.

Two harp traps were put in place: mine and a slightly larger one, each covering the entrance to one of the cellars. There is an art to siting a harp trap: it needs to cover as much of the entrance as possible and gaps need to be filled as far as possible, to prevent bats flying round the trap. A tarpaulin, some leafy twigs and an old coat were pressed into service around my trap:

It was quite cold, dipping as low as 5 degrees centigrade after sunset and bat activity wasn't high, apart from the large numbers of Soprano Pipistrelles (Pipistrellus pygmaeus) dispersing from their roost in a nearby farmhouse. Nonetheless, we caught four male Daubenton's, all of which emerged from one of the cellars. Frustratingly, it wasn't the cellar which had my trap at the entrance!

Two of the bats were recaptures and had been rung on previous visits to the site, but the other two were new and, as well as being weighed and having their forearm length measured, each had a tiny numbered aluminium ring slid onto it's forearm.

None of the bats had many parasites. This is often the case in spring, especially with adult males, which usually carry a lower parasite burden than females and juveniles. They are able to move between roosts to avoid parasite accumulation, whereas the females and juveniles are together in the maternity roost for several weeks each year, often with many other bats. I like to think that juvenile bats may also have similar personal hygiene issues to many human teenagers!

The picture above shows the fouth bat to be caught, who caught my interest as he had a tromiculid mite larva in his ear. The Trombiculidae are a large family of mites, including members of the genus Leptotrombidia, which parasitise bats for part of their life-cycle. Their larvae hatch within a bat roost, climb onto a bat and attach themselves, often in the bat's ear or on the forearm. There they take a meal, before dropping off the bat to become predators of other small arthropods within the roost during their nymph and adult phases.

I was particularly interested, as there are very few records of these parasites on British bats, partly because records of any bat parasites are rare and partially because they can be difficult to remove. Fortunately, this bat was quite placid and, with Carol-Ann (the "bat whisperer") holding him, I was able to paint the mite with a little isopropyl alcohol using a very fine brush, to make it release it's grip, and then remove it with fine soft forceps.

Once home I checked and have been unable to find any records of a trombiculid mite on a Daubenton's bat in the UK (unless anyone reading this knows better?), although that doesn't necessarily make it a rare species: probably just an under-recorded one. It will probably be a while before I am able to positively identify it to species: there are no field guides!

I haven't mounted the mite yet, but here's a rough and ready picture taken at x120. The larvae are usually a distinctive orange colour when seen on a bat. With their mouthparts buried in the bat, they look like tiny orange jelly beans.

As for the harp trap, it is still waiting to be christened with it's first bat. Watch this space...

Please note, trapping and handling bats without proper equipment, training and experience can be very harmful. Furthermore, in the UK it is illegal to do so without appropriate licences from Scottish Natural Heritage, Natural England, the Countryside Council for Wales or the Environment and Hritage Service in Northern Ireland.

If you're interested in getting involved in working with bats, the best starting point is your local bat group: http://www.bats.org.uk/bat_group.php

A checklist of mites found on British bats can be downloaded here: http://www.nhm.ac.uk/hosted_sites/acarology/saas/saasp/2003/saasp14.pdf

My website: plecotus.co.uk

What is it About Bat Surveys...?

Maybe it's the peculiar hours that bat-workers keep, or maybe it's the association with unusual animals, but there's a definite tendency for odd occurances and very odd characters to be encountered whilst doing bat survey work.

The people we meet range from the scarily enthusiastic, through the utterly barking and the dangerously misinformed to the simply peculiar. On one survey for Daubenton's Bats alongside a canal a bewhiskered Wing Commander type approached me and barked an enquiry as to what we were doing. When I told him he replied "That's alright then: I thought you might be looking for otters." I should probably have extricated myself there and then, but my curiosity got the better of me and I asked why he might ask that. In return I was treated to an extensive diatribe on the evils of the poor otter: how it kills lambs, despoils the countryside, wrecks fishing and probably bears off virgin maidens, causes global warming and harbours Osama bin Laden in it's holt. Where he had got all this rubbish from wasn't clear but it was obvious from the gleam in his eye that his opinions weren't open for discussion and I beat a hasty retreat.

On another occasion I was carrying out a dawn survey in a small park in Livingston, not a town noted for it's ethnic diversity. Just before dawn an enormous black gentleman jogged purposefully towards me, wearing colourful, flowing West African robes and fez hat and carrying a huge carved staff. He padded past me on bare feet without a sideways glance. Ten minutes later he returned in the opposite direction, still with the same purposeful, steady gait and again he acted as though I wasn't there, leaving me wondering if I was dreaming (at 4.30 in the morning that's entirely possible!).

In a town noted for it's UFO sightings I had to attend to a remote bat detector with odd noises emerging from it's radio receiver. When I reached it, I found two men with the case of the detector open, staring at the electronic gadgetry inside. I introduced myself and asked what they were doing. Their candid reply was that they though it might be a bomb, so they had opened it to see. What degree of utter stupidity led them to decide that it was a good idea to open a suspected bomb? Then again, perhaps they had a point: an Anabat detector belonging to the Highways Agency was recently destroyed by the Bomb Squad in a controlled explosion after it was found attached to a motorway bridge.

It's sometimes hard to understand chiropterophobia (or fear of bats), but for those it affects it is a very real problem. Last year I was checking a heated bat box on Ministry of Defence property. The sergeant on duty was built like the proverbial brick sh**-house: his muscles probably had muscles and I had no doubt that he could probably kill me with his little finger, whilst drinking a mug of NAAFI tea with the other hand. Nonetheless, it seemed a good opportunity to attempt some bat PR, so I explained what we had found and tried to show him a photograph on my camera. In a trice he was on his feet, backing away and shaking. I swear, if I hadn't calmed him down he would have reversed straight though the wall.

I was recently asked to look over some derelict council flats for any signs of roosting bats: a long day of methodically working through attic after attic. I expected them to be empty, as the occupants had long gone, but almost every attic was a treasure trove of the weird. One contained a knitting machine and enough wool to keep a knitware factory supplied for months. Another contained most of the body panels for a Ford Escort. Even odder was the attic in which several hundredweight of soil was lying in heaps, reminiscent of the PoW hut roofs in The Great Escape. Why? How? Your guess is as good as mine.

In case anyone reading this is feeling put off bat work I should stress that the odd situations and people are outweighed many times over by enormous numbers of warm-hearted, helpful and interested members of the public.... but the other sort are far more entertaining!

Please remember that some of the bat work described here requires a licence, issued by one of the four statutory nature conservation organisations. It is an offence to disturb bats or their roosts without one.

My website: plecotus.co.uk

Dawn Swarming

Someone once said that bats are hard to study "...because you can't see them and you can't hear them." It's certainly true that they don't give away their secrets easily, though bat detectors have allowed us to start the long hard job of understanding them.

A behaviour exhibited by most British bats which tips the balance a little on our side is dawn swarming, in whcih bats returning to a roost fly around the roost entrance for a period of time at dawn, often making false landings at the roost entrance. In doing so they give away the roost location. This is in stark contrast to evening emergence, when they dive out of the roost, flying hell for leather to avoid any possible predators, making it hard to spot where they have emerged from!

Of course the downside is that dawn is a horribly antisocial time of day to be about, something I was reminded of when my alarm clock went off at 2.45 am this morning. With dawn in Edinburgh at 5 am I wanted to be alongside a roost site at a suburban house well beforehand, to watch swarming develop. It wasn't just for fun: I had a suite of things I needed to know about these bats. All I knew was where the roost entrance was: at the end of a flat roof bargeboard, giving access to a hollow wall; and that they were Pipistrelles. I needed to find out which species they were, whether they were roosting in any other parts of the building and approximately how may bats roosted there.

For the first half hour there were steady comings and goings, with Soprano Pipistrelles (Pipistrellus pygmaeus) entering and leaving the roost in small groups and occasional bats flying close to the entrance in twos and threes. At 4.25 am swarming started, with numbers gradually building up to a peak five minutes before dawn, with around 60-70 bats zooming round the adjacent garden. You can see a brief snippet of the action here:

Soon after this bats started to enter the roost. Up until this point, everything was as I expected: no other part of the house roof was involved, I knew the species of bat and could see an approximate number. All I had to do was count them as they entered the roost, giving an accurate count and the job was done...or was it?

Only 30 bats actually entered the roost. The remainder gradually gained height until they were around 5-10m higher then the house, then one by one they flew off to the north-east. I have never heard of this behaviour before and was quite astonished to see it. Stuart Smith, of Lothians Bat group was later able to tell me of another roost site about half a kilometre away in that direction, so perhaps that is where they were heading. It is quite common for a colony to move around between several roost sites, but I have never before heard of them swarming at one site and then splitting up, to roost in mor than one location.

Whatever the cause, it was worth being up early to see the spectacle: the video doesn't really do it justice!

My website: plecotus.co.uk

The Hunting of the Noctule

For some time I have been rather fascinated by Noctule bats (Nyctalus noctula). One of Britian's largest bats, they emerge from their roosts earlier than other species and fly high abve pastures and river valleys, dipping down to catch larger insects. With a very loud call (reputedly louder than the legal safe limit for audible sound), their distinctive "CHIP CHOP" can often be heard from several hundred metres away.

You can hear a Noctule here: http://www.plecotus.net/noctule.mp3
(It was recorded in the Scottish Borders, using a hetereodyne bat detector set to 22kHz).

Traditionally they have been assumed to be largely absent from Scotland, apart from Dumfries and Galloway. It has been known for a while that the occasional Noctule turns up in the Scottish Borders and that there is a small population in the Tweed valley. More recently, there have a handful of records from reputable sources of Noctules in the Lothians, which led some bat-workers to query whether they are more widely spread than previously thought.

I set out to try to clarify this, by gathering together records from many sources across the Lothians and Borders area. I eventually gathered 41 records, from across the region, ranging from audio recordings validated by reputable ecologists to visual records of "large bats". That sounds like a lot of records, but they range over a period of eight years and twenty of these records relate to just 4 sites.


You can see a map of these sites here: http://www.plecotus.net/noctuleatlas.jpg


Hoping to locate more of these bats, I decided to use a variation on the car survey method, used for the Bat Conservation Trust Bats and Roadside Mammals Survey. This very successful technique involves driving at twenty miles an hour along country roads, with a bat detector poking out of the window, allowing many records to made in areas where bat-workers are thin on the ground (See below for the detailed method).


My theory was that, by doubling the speed to 40mph, a lot of ground could be covered in one session: typically 80miles in a session. The Noctule is a loud, high-flying bat, so mounting the detector on the roof and travelling faster should be feasible. The detector could be linked to the car stero with a wireless link, so that it's output would be clearly heard and we could stop and investigate when we heard anything suspiciously Noctule-ish. Thus, two nights ago, with Nigel acting as navigator, we set off in a vehicle decorated with rotating amber beacon and reflective warning sign to drive down the Tweed Valley and test the theory.


It was a perfect evening for bats: warm, dry and with plenty of flying insects around. We encountered an initial problem with air moving over the detector's microphone, causing unacceptable levels of background noise. This necessitated a speed reduction down to 30mph, after which the system seemed to work well and we soon started to hear Pipistrelles.

As a slight cheat we paused by the Dryburgh Suspension Bridge at Newtown St Boswells, a spot where there is usually a Noctule or two. Sure enough, a Noctule flew past and we could clearly hear it. Further on we crossed the Tweed at Coldstream and, after negotiating an unexpected diversion we found another bat near Wark. This was certainly a Nyctalus bat, but it is just possible it could have been a Leisler's Bat (Nyctalus leislerii). We heard only a couple of brief passes and the Leisler's has a similar call. Typically, we had two hand-held detectors linked to minidisk recorders and both failed at the same time! Without a recording to analyse and verify the bat's call we have to simply call it Nyctalus sp. Nonetheless, it proved that this variation on the BCT method is effective and worth persevering with.

You may ask, why not use the standard method? Firstly, 20mph is simply too slow to cover the vast amount of ground we need to survey and 30mph appears to work with these louder, high-flying bats. Secondly, the standard method requires some very expensive equipment and teams of four people, both factors which could be limiting. That in no way negates the amazing work that has been achieved by people in the UK, Ireland and elswehere using the BCT method.


The plan is now to carry out more surveys this year, focussing particularly on habitat that seems likely to be suitable for Noctules. To avoid making the same mistake twice, the audio from the roof-mounted detector will be fed via a lap-top, so that a permanent record can be made.


Anyone fancy a drive in the country?....


The standard method: http://www.ibats.org.uk/page.aspx?tabid=256


My web-site: plecotus.co.uk

Spring Has Sprung....

Three weeks ago I asked whether spring was springing yet, at least in terms of bat behaviour. We can safely say that Spring has now sprung. The chart below shows the night-time temperatures at Gogarbank meteorological station, near Edinburgh, since 1 April. It clearly shows that, after a brief blip at the start o last month, followed by a colder period, the warmer weather is now settling in.

(Met Office Data)

Last night Lothians Bat Group members returned to Blackford Pond and we found a big difference to the events of three weeks ago. For a start, we didn't have to tiptoe through hordes of amorous toads! Of more interest to us was the big increase in bat activity. At least 4 or 5 Daubenton's Bats (Myotis daubetonii) were foraging over the pond and finding plenty of invertebrates to eat. Above the footpaths were many Soprano Pipistrelles (Pipistrellus pygmaeus) and one or two Common Pipistrelles (Pipistrellus pipistrellus).

Whilst we were there, I was able to hook a frequency division bat detector up to a lap-top running Batsound software alongside the pond. Newer members of the group were able to see sonograms of the common species and compare them with the sounds, to help get a handle on the basics of bat call identification.

To give a flavour of the evening, here's a brief video clip showing two of the Daubenton's Bats over the pond last night. You can hear a heterodyne bat detector in the background.

We mustn't leave out the Pipistrelles: the most charming and delightful to watch of our native bat species. Here's a very short clip of a Soprano Pipistrelle feeding just before dawn this week, at another site in Edinburgh.

My website: plecotus.co.uk

Connecting Bat Detectors to Audio Equipment

This is the time of year when bat survey equipment starts to get dusted off and checked over, ready for the new survey season. Top of the list of course is the bat detector ( I can't even begin to understand what it must have been like to survey for bats before portable detectors was available).

Many bat-workers make recordings of bat calls they hear in the field, either so they can have a second attempt at identifying a bat at home, with a glass of something warming or, in the case of frequency division or time expansion detectors, to look at calls using Batsound or other call analysis software. I thought this would be an opportune moment to look at the connections between the detector, the recording equipment and the computer. It seems simple enough, but there are a few easy errors, which are less obvious than might be expected.

To understand how to connect things properly we first need to understand a couple of techy things about jack plugs and sockets:

Jack Plugs
There are several types of audio jack plugs, but virtually everything we are interested in uses 3.5mm jacks. There are two types: mono and stereo. The stereo plug is connected to three wires: one common and one for each of two audio channels (normally used to create that "close your eyes and visualise the orchestra" effect by producing slightly different versions of a music track in each ear). The mono plug has only two wires and, you've guessed it, only one audio channel.

Where it gets slightly tricky is that the mono and stereo jacks are the same size and fit into sockets intended for one another.

Sockets
There are four types of audio socket found on bat detectors and recording equipment:

1. Audio out (also labelled as headphone or speakers) is the socket on the detector or recorder which squirts out sound. The level is controlled by the volume control.
2. Line out (often labelled record) is the same as audio out, but with a steady volume, unaffected by the volume control.
3. Line in (also called audio in or sound input) is the socket on the recorder or PC through which the equipment receives audio.
4. Microphone in is similar to audio input, but is easily overloaded, as microphones produce very low level audio.

That's the geek stuff over. So, why does it matter? Most bat detectors are mono. As the two types of jack plug are interchangeable it doesn't really matter which we use. In fact it's helpful that they're interchangeable as it means stereo headphones can be used. A bog-standard stereo jack to stereo jack lead can be bought at Comet to connect the detector to a digital audio recorder, minidisc recorder or cassette recorder. Incidentally, avoid cassette recorders: the tape speed falls as the battery runs down, turning Common Pipistrelle calls into Nathusius' ones.

It's always advisable to connect the line out soocket on the detector to the line in socket on the recording equipment. That way, the machines take care of the audio levels and we can get on with looking at bats. Life being the way it is, some machines don't have these sockets, so we have to get a bit sneaky.

If there's no line out (or record) socket on the detector, it's necessary to use the headphone socket (and plug the headphones into the recorder's headphone socket, so we can hear what's happening), but it's necessary to make a few experimental recordings to work out what level the detector volume needs to be set to, to produce the clearest recordings.

If there's no line in on the recorder then it's necessary to use the microphone in socket, taking care not to overload it by having the detector volume set too high. The recorder's automatic level control will cause the background white noise to increase when there;s no sound, but it should drop the moment a bat is picked up.

The Bat-Box Duet
Things get more complex when using a Duet. These are excellent detectors, allowing the user to listen to a heterodyne detector, whilst recording what the user hears and the sound from a frequency division detector, one on each stereo channel. This permits later computer analysis. Admittedly, the sonograms produced are not quite as perfect as those made with recordings from a time expansion detector, but they're usually good enough for most purposes and it's much easier to use (anyway, how many hobby bat-workers can afford to pay a grand for a time expansion detector?)


The Duet achieves it's cleverness by using the two stereo channels: left for the frequency division audio and right for the heterodyne audio. As long as the recording equipment is also stereo then a standard stereo jack to stereo jack lead can be used. However, some digital audio recorders only have a mono microphone input. If you put a stereo jack in here the machine will record a weird amalgam of the output of both detectors. A cable which splits the stereo into the two mono outputs is required - see below. You need to go to a specialist shop like Tandy or Maplin, or if you're handy with a soldering iron, make one yourself.

The other difficulty comes when you replay the bat calls into a computer. If you don't have a line in socket on your computer the microphone socket may work, but it will be mono, rather than stereo, so the same cable is required.

Incidentally, if you're buying a minidisk recorder for use with a bat detector, check the line in socket carefully. Most have some sort of audio input, even if there's no line in socket, but a generation of minidisk players exists where the line in socket is a weird digital thing which looks like a 3.5mm jack socket, but simply doesn't work, except to record from other digital equipment.

Of course, all this should soon be academic, as we move towards bat detectors with built-in memory cards. Hopefully that will make redundant the geeky knowledge I acquired from my youth, spent making dodgy cassette recordings of LPs......

The BCT have published a useful guide to recording with digital equipment: http://www.bats.org.uk/helpline/documents/Digitalrecordingwithbatdetectors_005.pdf

More about the Bat-Box Duet: http://www.batbox.com/duet.html

My website: plecotus.co.uk

Finally, if you follow any advice here, you do so at your own risk.

Is spring springing yet?

When does Spring start? According to the Met Office, spring starts on 1 March, although the traditional start is the vernal equinox, on the night of 21/22 March. Here we are in mid April, so surely spring has started?

From a wildlife point of view, spring activity starts when the prevailing weather conditions permit, so in truth it's quite a variable thing, not just in terms of date, but geographically. The south of England is likely to experience signs of spring one or two weeks before they appear here in Scotland.

With some members of Lothians Bat Group, I went to Edinburgh's Blackford Pond after sunset, one evening last week. If you live in Edinburgh this is a great place to see large numbers of Daubenton's Bats (Myotis daubentonii) and Soprano Pipistrelles (Pipistrellus pygmaeus) in the summer, and the group usually run a bat walk there every year. On this occasion we wanted to see if there were the first signs of bats emerging from hibernation yet.

With an ambient temperature after sunset of just 2.5 degrees celsius, it was questionable whether we'd see any bats at all, but what was probably a lone Soprano Pipistrelle passed by a couple of times and we watched one, and later two Daubenton's Bats feeding on the pond. There was very little food for them, so they were having to range over the whole of this large pond, to find enough flying insects to eat (they looked to be small Sedge Flies). With such a low temperature, it's possible that these few bats were some of last year's juveniles, desperate for food after the long months of hibernation.

So is it spring? Well, not really from a bat point of view, as it seems like the main population are still in hibernation. The graph below shows the night-time temperatures at the Gogarmor meteorological station, to the west of Edinburgh, since the start of April. As you can see, there was a brief peak of warmer temperatures at the start of the month, but it has been quite cold at night since then.

Having said that, there are other signs of spring. As we walked around Blackford Pond, we had to tread carefully to avoid a large number of toads, commuting towards the pond, in order to mate?

Since then I have also seen some discarded eggshell from what must be a very optimistic bird and last weekend, I watched a group of Brown Hares (Lepus europaeus), boxing and chasing each other: the so-called "mad march hare" behaviour, associated with the onset of the breeding season. This behaviour actually continues through to September, but is far more noticeable just now, whilst the grass is short.

Hopefully we'll get a spell of warmer weather soon, and we'll start to see more bat activity, as the adults move out of their hibernation sites and the move towards maternity roosts commences, ready for the breeding season around June. My bat detectors are charged up and ready...

My website: plecotus.co.uk

"Untold riches" of swarming bats...

I am officially conferenced out, having spent the last three days in York for the
Mammal Society Conference. It was definitely worth going: I'm buzzing with thoughts about Irish hares, Beaver management in Bavaria, small mammal survey trials and much else besides. It's a little disappointing that there were no papers on bats, but that was more than made up for by Professor John Altringham's Cranbrook lecture.

John's team from Leeds University have carried out a large and complex study of bat swarming behaviour at caves in the Yorkshire Dales and the North Yorkshire Moors. Autumn swarming is a behaviour which is increasingly seen as an important part of the annual cycle of bats, especially Myotis and Long-eared species. Bats gather at hibernation sites, usually caves and mines, to check out the site, to help young bats find it and for courtship and mating. Swarming is typified by chasing behaviour late into the night, often peaking three or four hours after sunset and takes place during August to October.

They looked at Natterer's Bats (Myotis nattereri) and, by ringing bats at known summer maternity roosts and then harp trapping at swarming sites, were able to demonstrate that bats wer flying up to 60km to a swarming site. They were also able to demonstrate that huge numbers of bats were using these sites: up to 400 per night, with considerable turnover between nights. Furthermore, by comparing data year on year they were able to demonstrate high fidelity: bats tend to return to the same site each year. The conservation implications are huge: these sites can provide a key part of the lifecycle of very large numbers of bats, from a wide geographical area.

What struck a chord with me was the fact than John described the importance of these sites and went on to mention that it was then usual to find only a handful of hibernating bats within the caves, as many were not visible. In other words, some of the hibernation sites we survey in the Scotland could be swarming sites for similarly large numbers of bats. Not for nothing was one of John's conclusions the possibility of "untold riches" for bat-workers.

This tiny hole, high in the hills in South-west Scotland, gives access to a tunnel over half a kilometre long, which contained 9 Natterer's Bats and 1 Daubenton's. Could this be a swarming site on a similar scale to the ones in the Yorkshire Dales?

Another intriguing part of the lecture related to a study in which John's team compared the numbers of hibernating bats to the physical features of a cave or mine. They found that the size of entrance was irrelevant ("if you can get in, they will"), as was the altitude, the orientation of the entrance and the habitat nearby. What makes a good hibernaculum is large spaces inside, a reasonable depth, some cover near the entrance and not too wet. This struck a chord with me, as we've done several surveys in the past winter of a limestone mine, which seemed to have all the right features of a hibernaculum, but we never found any bats. John's conclusion was "the more water, the fewer bats", which seems to fit.

I must finish by plugging the Mammal Society's new edition of "The Mammals of the British Isles". It's not cheap (and you may need to reinforce your bookshelf to take the weight), but it is worth every penny. If you buy a copy via the Mammal Society website, all ofthe profit will go to the society.

John Altringham's Leeds University web-page: http://www.fbs.leeds.ac.uk/staff/profile.php?

The Mammal Society: http://www.abdn.ac.uk/mammal/

My website: plecotus.co.uk

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

Bats, bombers and acoustic mirrors

One reason why I first started working with bats was that bat work combines my love of wildlife with my longstanding interest in electronics. Fortunately people who do surveys with me tend to tolerate my tendency to come up with strange new ideas or pieces of equipment!

Several years ago I found myself wondering whether parabolic dishes might have a place in bat work. These are used in the recording of bird calls and other wildlife sounds and look similar to TV satellite dishes. In essence, the dish reflects sounds into a focal point, where a microphone is placed. This has two effects:

1. Sounds are concentrated by the dish, making them louder.

2. Sounds are picked up from a narrow direction, filtering out background sounds from either side.

Incidentally, not just any dish will work: a parabola is a specific curve, calculated using a mathematical formula.

I experimented with an old Sky TV dish and found that when I put a bat detector at the focal point of the dish, bat calls became louder and so could be heard from further away. However, it was clear that this would have limited practical uses, as it only worked when the dish was pointed directly at a distant bat. People recording bird calls can see a bird and point a dish at it. Bats don't allow that luxury!

More recently I became aware of something called a parabolic plane. This is sometimes used in microwave radio applications. It is like a dish, but only curved in one plane, a bit like Rolf Harris's wobble board. Between the wars gigantic parabolic planes up to 200 feet long by 26 feet high were built at strategic sites around Britain's coast. These "acoustic mirrors" were used to listen for approaching bombers: operators could hear an aircraft from 20 miles away. Unfortunately they were never used for their intended purpose: by the time World War II broke out, radar had taken over.

Image (c) English Heritage

The beauty of a parabolic plane is that it only concentrates sound from the horizontal plane, so that a bat flying in front of one at any height should be heard. It could be possible to create a kind of listening curtain: in theory any bat passing through it would be detected. To test this I made up a prototype reflector, using foam board, card and sticky-backed plastic (eat your heart out, Blue Peter) and tried it, using a low-level ultrasound source as an artificial bat.



The prototype is only 60cm by 20cm, so I wasn't expecting miracles, but tests at varying ultrasound levels showed that, using the reflector a Duet bat detector could pick up the artificial bat between 30% and 70% further away than it could on it's own. Positioning of the detector microphone is critical, as it needs to be at the precise focal point of the reflector for best results. The half-brick will need to be replaced by something with a bit more finesse!

There is some interesting potential for parabolic planes, but there are some potential draw-backs too. In theory, the bigger the reflector, the further away you can hear bats. But a bigger reflector also means the bat would be audible for a shorter time, passing through a narrower curtain. (The acoustic mirrors could hear aircraft from 20 miles away and place them to within 1.5 degrees.) Ideally a bat needs to be audible for 1-2 seconds, to be sure enough of it's call is
recorded, to allow for identification, so this may limit possible size..

Another problem is the practicality of lugging a big reflector around. Even using it in a fixed position, more than 2-3 metres in width would probably be impractical, unless as a permanent fixture. Any fixed-location survey involves predicting where the bats will fly, and they don't alway read the same books as us!

More about acoustic mirrors: http://www.ajg41.clara.co.uk/mirrors/

My website: Plecotus.co.uk

Right-diddly-wotsit squirelly

If John Donne had been an ecologist, rather than a form of suffering for High School English students, he might have said "No bat is an island". That's an appalling piece of paraphrasing and as I write it I find myself glancing over my shoulder, in fear of an avenging teacher. However, my point is this: as bat ecologists it is very easy to become entirely focussed on "our" species and lose sight of their place within the ecosystem.

With that in mind (and because the bats are far from active at present) I present a small diversion from the world of bats, into the world of bryology: the study of mosses and liverworts. Where's the relevance? Woodland is probably the most important habitat for bats and a key part of woodland structure are the mosses and liverworts. In some British woodlands they outweigh vascular plants in terms of biomass and they form an important habitat for many invertebrates which may ultimately become bat-food. Also, I like them and it's my blog.

With over 1,100 species of bryophyte in Britain, some hard to identify, there are limits to what a casual naturalist can achieve, but to show that this is no excuse, here's my guide to five common woodland mosses everyone should be able to identify, even without a hand-lens. Just to prove my point, they were all photographed in my local (rather poor) woodland this afternoon, whilst walking the dogs.

Rhytidiadelphus squarrosus (Right-id-aye-ah-dell-fuss squaw-row-suss)

If you're a keen gardener you probably know this moss already. It's common name is Lawn Moss, for good reasons. In woods and lawns it often forms dense carpets and is very easy to identify: pull up a bit and you'll see it has a bright red stem and green leaves, which are squarrose: they emerge from the stem and bend downwards.




Thuidium tamariscinum (thoo-id-ee-um tam-ah-riss-eye-num)
My personal favourite, this plant is very easy to identify. It is regularly tripinnate, meaning that the stem is symmetrical, with each branch off the stem divided into sub-branches, which are themselves further branched. In other words, it looks like a miniature fern. The stems are always green or black (if red, you've got Hylocomium splendens) and quite springy, so the little fern-like stems often arch over, like a bramble. It's common name is Tamarisk Moss.



Dicranum scoparium (die-crane-um scop-ah-re-um)
This is an upright moss, often forming dense tufts. The giveaways are the long, thin, pointed leaves, often densely packed together and turning to one side. It's common name is Fork Moss.





Sclerapodium purum (scleh-rah-podium poo-rum)
The leaves of this moss lay along the stems and branches, tightly overlapping, giving them a bloated, fat look, with blunt tips. This feature gives it it's common name: Neat Moss. It's regularly pinnate, so the branches are roughly the same on each side of the stem and they aren't sub-branched. It should have a green stem, if it's red you may be looking at Pleurozium schreberi.




Plageothecium undulatum (play-gee-oh-thee-see-um un-dew-lah-tum)
This is a very easy moss to identify. It forms loose mats of pale green, flattened stems, usually unbranched. If you look very closely at the leaves they are undulate: in other words, wavy from end to end. Hence the common name: Wavy Flat-moss.

Having got that out of my system I can go back to talking about bats...

There is unfortunately no good field guide to mosses and liverworts currently available. However, the British Bryological Society are working to rectify that. You can view the whole of their new field guide on-line (but be aware it's a work in progress): http://hosting.sleath.co.uk/bbs/

In the meantime, Carol Crawford has published a very nice guide to common woodland mosses, and it's not expensive (£6.50): Carol L. Crawford (2002) "Bryophytes of Native Woods" (3rd ed.) Natural Resource Consultancy ISBN: 0-9543795-0-0

Many thanks to Nick Hodgetts, David Chamberlain, Alex Lockton and Sarah Whild, without whom I'd still be asking "what's that little green squishy plant?" Incidentally "Right diddly-wotsit squirrelly" was my daughter's exasperated response when I tried to teach her some bryophytes...

My website: plecotus.co.uk

The name of the bat

I can't help thinking that the English language has failed to play fair by the bat. I mean what sort of word is "bat" to describe such a graceful, enigmatic and fascinating animal? The one distinction the word has is that it was given to a Royal Navy destroyer, HMS Bat, built in 1896. HMS Bat served in the Mediterranean and in home waters during the First World War, before being sold for scrap in 1919. The name was revived during World War II for a naval tug.

So where does this odd little word come from? It is thought to be derived from the middle english word for the bat: bakke, possibly as a result of confusion with the latin word for a night-flying insect: blatta. Bakke itself is likely to be a shortened version of the old Danish word for a bat: natbakka, or "night flapper". Sticking with our Scandinavian forebears, the old Norse had a wonderful name for them: leorblaka, which means "leather flapper". That name must come from someone who had seen a bat's wing close up. It's such an evocative name it's almost worth reviving it!

Other forebears of ours (an awful lot of old races contributed to Britain over the years) also had some interesting names for the bat. The old english word for bat is hreremus (pronounced rear-mouse), meaning "shaky mouse". Whoever came up with that name had certainly watched a foraging pipistrelle!

When the Romans came to Britain they brought the latin word for bat: vespertilio, derived from vesper, their word for "evening". From this comes the family name for all our British bats, apart from the two horseshoe bat species: vespertilionidae. It's also the original root for another bat word. In old Italian vespertilio became vipistrello and thence the modern Italian word for bat: Pipistrello, which of course led to Pipistrelle.

Other modern European languages have interesting names for bats. The Germans say fledermaus, literally "flying mouse". For an ecologist, trying to convince people to live in harmony with bats, it's a little disappointing that so many names for bats refer to mice, at risk of tainting bats with their image as vermin. I suppose it's inevitable.

The French use the word chauve-souris, which translates literally as "bald mouse" This seems odd, until we discover that it's derived from the ancient Greek calva sorix, meaning "owl mouse", which makes more sense.

For me the prize must go to the Spanish. Their name for the bat is derived from the latin mures caeculus or "blind mouse". That's bad on two fronts, as the bat is neither blind nor a mouse, but all is forgiven, because in modern Spanish the word becomes murcielago, the name given by Lamborghini to one of the fastest and most lavish supercars in the world.

That's more like it!


My website: plecotus.co.uk

The Versatile Bat Detector

The most basic tool of the trade for a bat worker must be the heterodyne bat detector: the pocket-caculator look-alike that allows us to listen in to the sounds made by bats. Not only does it help us find bats, it often allows us to identify them to genus or species, to tell when they are feeding and to hear their social calls. It would be easy to be satisfied with that little lot, but the humble detector has other uses too.

Being pedantic, "bat detector" is the wrong name for the machine, as it implies that all you will hear on it are bats. This may stem from our tendency to talk about ultrasound as though it were something special and magical. In reality, ultrasound is simply sound above about 20kHz in frequency. The only thing that sets it apart from sounds below that frequency is the fact that one rather arrogant species with an abysmally poor hearing range can't hear it!

Many everyday things produce ultrasound: pouring water creates a loud noise around 40kHz. The standard test of whether a detector is switched on is to rub your fingers together in front of the microphone, a sound which is much louder around 45kHz than it is at frequencies within our hearing range. "Dry", rustling sounds tend to be much louder at higher frequencies: when our alsatian jumped into a huge pile of dead leaves behind me whilst I was using a detector with headphones, I though I was going to be deaf for life...

Bats aren't the only species which produce ultrasound. A common summer hedgerow sound is the high-pitched, furious squeaking of squabbling shrews. The lowest frequency of that call fall just withing our hearing range (older people may struggle to hear it at all), but on a bat detector tuned to about 20-40kHz they are very clear. In 2005 I and some colleagues from the BATML project were conducting a series of surveys along the towpath of the Union Canal. We kept hearing shrew sounds from one particular place by the water's edge. It was noticeable because these calls were extremely loud and unexpected. When you've had cause to swear loudly at something, it sticks in your mind! The Mammal Society were running their nationwide Water Shrew (Neomys fodiens) survey at the time, so I placed some tubes, baited with casters (blowfly pupae) and sure enough, the scats left in them were confirmed as having been left by a Water Shrew. This was particularly nice as it was the first record of this species from the Lothians for almost 20 years.

Another branch of natural history in which bat detectors are increasingly finding a place is in the study of Orthoptera: grasshoppers and crickets. It is possible to accurately identify them to species by listening to their sounds. Although many can be heard with the naked ear, they are clearer and louder when heard on a bat detector. Unlike bat (or shrew) calls, these sounds have no frequency variation, as they are stridulations, rather than calls, i.e. the sounds are made by rubbing legs together. Identification is made by listening to the rhythm of the sounds. As the insects tend to stay in one place whilst stridulating you can use the detector as a direction-finder to home in on them.

There's a good introduction to Orthoptera id using a bat detector on the web-site of the Environmental Records Centre for Cornwall and the Isles of Scilly (ERCCIS), along with a lot of other useful resources: http://www.erccis.co.uk/species/orthopteraaudio.htm

The Mammal Society's water shrew survey page: http://www.abdn.ac.uk/mammal/water_shrew_survey.shtml

The Bat Conservation Trust (BCT) website has a guide to choosing a bat detector. The models mentioned are mostly out of date now, but the technical advice is very sound: http://www.bats.org.uk/helpline/documents/Whichbatdetector.pdf

For what it's worth, I rate Bat-Box detectors as the best. They have the ideal balance of cost, effectiveness and sturdiness in the field. They're slightly cheaper if you buy direct: http://www.batbox.com/

My website: plecotus.co.uk

Time Team vs Bat Team

My favourite TV programme is Channel 4's "Time Team", in which a team of archaeologists dig a historic site and attempt to make sense of it in just 3 days. Although the practical archaeology is interesting, for me the best part is when Stuart Ainsworth and Mick Aston take to the air and attempt to tie their site into the surrounding area. A Roman villa or iron age settlement is all very well, but when you can identify how people travelled to and from it, where they fished or went to market and why they might have chosen that particular place, it all makes so much more sense.

Surprisingly, there are strong parallels with bat work. We tend to concentrate on roosts and hibernation sites. And why not? They are the focus of the bats' activity: where you can conduct a roost census or watch bats swarming. If you have a reason (and licence) to trap and examine them, this is the best place to do it. Roosts are so much more exciting. Roost sites can be hard to find and of course they are where a population of bats may be at its' most vulnerable and in need of protection. Anyone can go for a walk with a bat detector and find a bat in flight, can't they?

Possibly they can, but with a bit of planning and focus, finding bats in flight can help to build up an understanding of how bats use the landscape, in the same way that "Time Team" try to work out how Romans or celts did.

Here's a simple example. Last year I was conducting a series of sunset surveys in some farmland, where a water pipeline was due to pass through. In two places I noted large groups of Soprano Pipistrelles (Pipistrellus pygmaeus) feeding soon after sunset. This can be an indication that a roost may not be far away. An even better indicator is a commuting bat. Bats commuting to and from their roost at dawn and sunset tend fly fast in a straight line: they're on their way somewhere, so why waste energy flitting about, as they might when foraging? A bat flying fast, and straight at dusk, is therefore a good indication that the roost lies in the direction it's coming from. When it's followed by other bats doing the same there is a good chance it isn't far away.

The next survey was in a path running through a strip of woodland. Over twenty Sopranos passed through at sunset, all going in the same direction, the direction of one of the foraging sites I had previously noticed. Soprano Pipistrelles usually roost in buildings and the large-scale map showed a Victorian lodge half a kilometre away, right in line with where they were coming from. I dragooned some help and the next morning we were lying in wait for them near the lodge. But no bats arrived. Spreading the net a little wider, we came across about twenty bats, swarming in the corner of a field. Just to confuse us, there were no buildings close to where they were swarming )they would normally swarm in front of the roost). It turned out they were roosting in a tree, which is quite unusual for Pipistrelles in Scotland. It took another couple of visits to work out which tree the bats they were using: a mature oak.

It's always nice to find a new roost, but the icing on the cake was to also have an understanding of how they were using their habitat. I hope to find time this year to look at some of the other hedgerows and woodland edges which radiate out from the site, and try to work out what other commuting routes are used, adding to the picture of how these bats are using their landscape.

Of course, it'll take more than the three days that "Time Team" get....

The field where we found the Soprano Pipistrelles swarming at dawn. No, the oak tree in the middle isn't the roost: that would be too easy, it's to the left, out of sight.

My website: 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"). 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

My website: http://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/

The kitchen table harp trap

For some time I'e been thinking about building a harp trap for my own use and I'm delighted to say that this winter I have finally found the time to do so. What is a harp trap? Also called a Tuttle trap (after Merlin Tuttle, whose invention it is), it's an ingenious trap which catches bats in flight, without harming them.

It works like this: a bat flies towards the trap and recognises a harp-like collection of vertical nylon lines about 2.5cm apart. With great agility it successfully flies between the lines, but what it doesn't expect is a second set of lines offset from the first, so that it can't avoid hitting them. It then slides unharmed down the lines, into a canvas bag below. The bat will try to climb the side of the bag, so it can take off again, but the sides of the bag are lined with thick, slippery polythene. The bat can climb the canvas, but soon reaches the seam where it is joined to the polythene and can go no further until it's removed.

Harp traps can be marvellously effective, when used properly. They are particularly good at trapping bats leaving roosts, as the bats have less time to see and avoid the trap than they would if they were free flying. More importantly, the bats are entirely unharmed and in my view suffer less stress than if caught in a mist-net. The problem is the cost: a single harp trap costs upwards of £800. See http://www.faunatech.com.au/products/harptrap.html for pictures of a commercial trap made by Austbat.

I reckoned that I could reduce that cost to under£200 by building my own trap, and add a few ideas of my own. Firstly, I wanted a smaller trap. With a catching area 1.8m wide and 2.4m high, the Austbat trap is unwieldy in some circumstances. It is also difficult to erect, as it is necessary to unroll and stretch the lines every time the trap is used. This process is fraught with difficulty at the best of times, let alone in darkness and pouring rain, when you're tired and fed up at 2am! My thinking was that a smaller catching area could allow for the harp section to be permanently erected within a frame. When not in use, the frame could be bagged , with the legs and catching bag removable for transport. A smaller trap would also be lighter and could be lifted on a couple of poles to cover the entrance to a high tree roost or the eaves of a roof. You can do that with an Austbat trap, but you need ropes and a team of stout people singing sea shanties, to haul it up!

And here it is...

The catching section is slightly over 1m square, with the frame, legs etc, made from lightweight square-section aluminium, which also has the advantage of being an easy material to work. The legs are easy to remove, without affecting the rest of the structure, so that the frame can be slung between two poles and lifted up to a roost entrance.

I took the opportunity to address two weaknesses I've noticed with the Austbat and similar traps. They have the nylon monofilament tied around the frame top and bottom. This has the effect of making the nylon vulnerable to scraping against rough surfaces and fraying or breaking. I tried to address this by tying the nylon lines to tiny hooks screwed into the frame, so that the frame itself protects the nyon.

The Austbat traps are also vulnerable to escapes at each end of the bag, as the plastic material is only attached to the two long sides. I have made a point of attaching plastic to the two short sides, in the hope of preventing that. The base of the harp frame sits slightly inside the bag, to allow this to be possible.

The hardest part of building the trap was sewing the canvas and plastic. Dressmaking isn't a skill of mine anyway, and it takes a lot of effort to push a sailmakers needle through several layers of the thick canvas. My fingers may never be the same again!

Where does the kitchen table come in? That's where I built it (it's too damn cold in the garage at this time of year!) The table still bears the scars.

Of course, I'm rather proud of the trap, but success isn't realy measured by appearance, or sound engineering or even my pride - it's measured by whether it actually works: will it catch bats?

Watch this space...

Please note that the use of a harp trap to catch bats in the UK is heavily restricted. I am able to use one because I have a roost visitor's licence, endorsed for the use of a harp trap, I am also licenced to catch a number of bats for a specific scientific study. Trapping bats without he necessary skills and licence is illegal and likely to be harmful to the bats. If you're interested in getting involved in this kind of work, the best starting point is to join your local bat group.

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

Armchair roost-searching

The holy grail of bat-work is finding roosts. Finding and watching feeding or commuting bats is great but the roost sites are the centre of the network of bat activity. More importantly, if we know where roosts are, we can ensure they are safe from disturbance or destruction.

So how do we find new roost sites? Basically, it involves one of three methods, though all three require a great deal of luck!

Method 1 is to seek out commuting bats and attempt to let them lead you to the roost. Great fun, and sometimes very successful, although hard work.

Method 2 is to simply stumble across one. Bat calls from worried householders can bring new roosts to light. Many bat-workers have had someone say casually "Bats? Oh there are hundreds of them in our attic - you should come and see them." A remarkable number of people have bats in their homes, are perfectly happy and don't make any fuss about it.

Method 3 is to carry out a dawn survey: bats tend to swarm around the entrance to their roost for 20-30 minutes just before dawn, so looking for them can be quite effective.

Whichever approach (or approaches) is used, some homework helps provide the best return for time and effort, and this is the ideal time of year to do it. We're lucky to live in an internet age and the web is stuffed with handy resources.


The NBN (National Biodiversity Network) Gateway houses a lot of records of roosting bats in Scotland, though it seems patchier south of the border. Go to http://www.searchnbn.net/, type a species name into the search box and then select the interactive distribution map. This is a handy (though slow) gadget which allows you to navigate your way around the records held. Unless you make special arrangements with data providers, you can only view the records at an accuracy of 100m, but that's a starting point for a roost search. Don't assume a record means that a site is known about. I recently found six local records of Brown Long-eared Bat roosts, which weren't know about in our local bat group. Remember also that an absence of records may mean a shortage of bat-workers, rather than a shortage of bats!

Maps are, of course essential for this sort of work. The Ordnance Survey have made their mapping available on-line, as an interactive tool. In my view nothing can ever replace a dog-eared 1:25 000 scale map, complete with coffee-stains and ten years-worth of pencil marks and scribbles, but I have to admit that the Get-a-map service is extremely convenient! http://www.ordnancesurvey.co.uk/oswebsite/getamap/

Some bat roosts are found in historical man-made structures: old buildings, bridges, mines, lime kilns etc. The Royal Commission on Ancient and Historical Monuments Scotland (quite a mouthful!) have an on-line database of archaeological site records called CANMORE, which can be searched either manually or via an interactive map. This is similar to the NBN Gateway, but faster. It's a terrific resource, which I've been using recently to search for potential hibernaculum sites, such as world war 2 pill-boxes, disused mineworkings etc. Go to http://www.rcahms.gov.uk/search.html and try a CANMORE search. Even if you don't find a potential roost, you'll be amazed what archeologists have found near where you live!


Once we have a site which may be of interest, what can be done next? Taking a close-up look from the air may help. Windows Live Search offers an interactive satellite photograph service, similar to the well-known Google Earth, but with significantly better coverage. Go to http://maps.live.com/ and try zooming in to the site of interest. If your site is in a high definition area, not only can you zoom in close and see what it looks like, you can also get a sense of the surroundings habitats, flyways, foraging potential and so on. It's also a damn good toy just to play with! (I know the photographs of York were taken on a Tuesday because my Mum has her washing on the line!)








Knowing my luck, summer will come along and I'll be too busy to follow up these sites, but at least I will have had a winter bat "fix" and being familiar with these resources often comes in handy with all sorts of fieldwork planning.


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

I want to live in Poland!

I had the privilege today of hearing a fascinating presentation by John Haddow of Central Scotland Bat Group about the Nietoperek Bat Reserve in Poland.

Nietoperek is something of a legend in the bat world: a massive underground system of world war 2 fortifications: with 32 kilometres of tunnels, an amazing thing in itself. But what really adds the thrill is the fact that they are used as a hibernation site by mind-boggling numbers of bats.

For several years John has been taking part in the annual census of hibernating bats, when a large group of skilled bat-workers from across Europe come together to count the bats in the tunnel system. The numbers are incredible: over 30,000 bats were present this year. The predominant species are Greater Mouse-eared Bats (Myotis myotis), with many other species represented, including Daubenton's Bat (Myotis daubentonii), Natterer's Bat (Myotis nattereri), Brown Long-eared Bats (Plecotus auritus) and Barbastelles (Barbastella barbastellus).

Why do they gather in such huge numbers and (more importantly for us!) why don't they do so over here? The numbers of bats we see in Scottish hibernacula are tiny by comparison! According to Frank Greenaway, it's all a matter of our Atlantic climate versus the continental climate of Poland. Put simply, it gets a lot colder in winter in Poland and stays that way for longer, so bats have a greater imperative to find an underground site with a stable temperature.

I also came across a wonderful new word: Chiropterology: The visitor centre near Nietoperek is called The Chiropterological Information Centre. I now know what to say when people who know nothing of ecology ask what I do for a living: I'm a chiropterologist!

The Chiropterological Information Centre: http://www.mos.gov.pl/strona/pl/cicinfouk.htm

Frank Greenaway's video on bat torpor: http://www.nhm.ac.uk/nature-online/life/mammals/webcast-torporinbatsvid/no-mamm-torporinbatsvid.html

This site describes a visit to Nietoperek: http://www.iol.ie/~corkbatgroup/Nietoperek.htm


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

Life in a hostile habitat: the wing of a bat

For several years I have been taking a close interest in bat parasites. Indeed, as I write this, to the side of my laptop are a stack of specimen storage vials containing over 400 parasite specimens, taken from over 80 individual bats.

Many of my bat-worker colleagues find this interest hard to understand. Admittedly, they do not fall into the charismatic megafauna "cute and cuddly" bracket, but many are impressive animals in their own right.

Spinturnicidae are the largest and most obvious of the mite families, which use bats as their hosts. Superficially like miniature claw-less crabs, they live out their entire lives on the wing and tail membranes of their host, never leaving the bat, except to pass to a new host. Unlike many ectoparasites, they do not take refuge in the bat’s fur.

The wing membrane is a mind-bogglingly hostile habitat: in flight the wings flap 10-15 times per second, requiring immense grip and an aerodynamic profile to stay attached. Like all mammals, bats regularly groom themselves, and unable to hide in the bat's fur, these mites need to make it difficult for the bat to dislodge them from the wing. Vulnerable eggs or larvae would not survive long.

To survive in this difficult habitat Spinturnix mites have several adaptations:

• Their short, stout legs are extremely strong.


• Feet are equipped with large claws and sticky-hooked pads, to cling on.


• The body is flattened and armoured with chitinous plates.


• Egg & larval stages are completed within the female's body.


• The female gives birth to a single protonymph,

Removing Spinturnix specimens from the bats is an uphill struggle. As soon as the mite realises it is threatened it either runs across the wing membrane (and they're fast), or it hunkers down and grips the membrane tightly. Either way, the best way to remove them without risk of harming the bat is to dab it with a drop of ethyl acetate or 70% alchohol, which usually dampens it's ardour.

Having gone through the difficult processes of catching a bat, then removing the mite, the fun is only beginning! Attempting to identify of bat mites has led me to seek documents published by the Zoological Society of London in 1923, by the University of California in 1960, and most recently a Russian-language parasitology journal! But it's all good, clean fun....

Pictures:

Top - Daubenton's Bat Myotis daubentonii, showing the wing membrane.

Middle - Close up of the wing membrane, with a Spinturnix myoti mite.

Bottom - Adult female Spinturnix myoti.

Anyone wanting to study bat parasites in the UK is lucky to be able to draw on the work of Anne Baker of the Natural History Museum. With Jenny Craven of Leeds University she produced a checklist of species in 2003, which is available on the web: http://www.nhm.ac.uk/hosted_sites/acarology/saas/saasp/2003/saasp14.pdf

Please note, trapping, handling or otherwise disturbing bats in the UK is illegal without a licence from one of the statutory nature conservation organisations (SNH, CCW, Natural England).

My website: plecotus.co.uk

Two roosts for the price of one

Many commercial building surveys for bats result in a big fat nothing (often they are requested simply to confirm the absence of bat roosts prior to demolition or renovation), so it was nice recently to find one building with two separate roosts.

Obviously, I can't say on here where the site is, but with great riparain and woodland habitats at hand, plus several large attic spaces, it was a promising site. The first attic space I entered revealed many accumulations of bat droppings, mostly running in a line below the ridge. This was because the bats had been roosting in the space between the fibreboard lining and the roof tiles. Droppings had fallen into the attic through gaps in the fibreboard and these gaps were particularly prevalent at the ridge. Given the small size of the droppings, the large quantitiesof them and the fact that the bats clearly have an affinity for crevices, makes it likely that they are one of the Pipistrelle species, but I can't be certain of that until they return to the roost later in the year. (An advantage of being in Scotland, with a limited range of bat species: I would be far less willing to make even tentative suggestions as to species if I were in the south-east, where there are more than twice as many species!)

Incidentally, you can tell bat droppings from mouse droppings because, although they are a similar tiny size and cylindrical shape, bat droppings tend to be much darker and have a "knobbly" texture because they are largely made up of pieces of hard chitin from insect ectoskeletons. If you rub a bat dropping between your fingers it will usually turn into a gritty dust, whereas the mouse dropping will probably squash between your fingers (yum!). In the pictures you can see how some of the older droppings are turning grey.

The second roost was in a separate attic space. The droppings there, instead of being concentrated in piles, were scattered everywhere. They were also a little larger than the others and had a slightly shiny appearance. It's possible these were left by Brown Long-eared Bats (Plecotus auritus), which tend to roost in the apex of an open attic space and fly around to warm up before emerging from the roost. Later I analysed some of these droppings under the microscope and the shiny appearance was caused by large quantities of moth scales. (Excuse the picture quality below - photomicroscopy isn't my strong point!) Moths form a significant part of BLE food, especially in Scotland, but again, I won't know what species they are for certain until they return later in the year.

If you fancy trying bat dropping analysis (it really isn't as horrid as it sounds) try to get hold of a copy of "Identification of Arthropod Fragments in Bat Droppings" by Caroline Shiel et al, published in 1997 by the Mammal Society. (Try Pennine Books http://www.penninebooks.co.uk/)

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

What's in a bat box?

Well, hopefully...bats.

When the first bat-box schemes were launched, in the 1970s, using sponsorship from viewers of BBC TV's "Nationwide" programme, there was one design: the standard wooden bat-box. They're not unlike a blue-tit nest-box, but instead of a hole on the front, the bats access by climbing a roughened board and entering through a narrow slit at the base. Easy and cheap to make from a single plank of rough timber, there must be many thousands of them around the country and they're as effective as ever.

Bat boxes do a great job of supporting bat conservation by raising awareness, providing an easy way of monitoring local bat populations, and by providing bats with roosting opportunities in places where alternatives are limited. Annual bat box occupancy checks carried out by local Bat Groups also give a great opportunity for novice bat-workers to see bats close up (strictly supervised by someone with an appropriate licence).

Today, many designs are available, to the extent that choosing bat-boxes is almost as hard as choosing a new car! Do we want it to emulate narrow crevices, to suit Pipistrelles, or bigger tree-holes, to suit Noctules? Do we want cheap and cheerful wooden construction, or shall we push out the boat and use deluxe woodcrete bat-boxes? How about a wedge shape? Should the door be on the top or at the front? Should it be painted black? And so on...

Here in the Lothians, a bat box containing anything other than Pipistrelles is sadly a rarity, though a box full of Pips is still a welcome sight. Whilst the traditional boxes are well-used, they seem to prefer slimmer, more crevice-like designs. However, the most popular design seems to be the dome-shaped woodcrete (a cement and sawdust mix) boxes, made by Schwegler. They're not cheap, but the occupancy rates are definitely higher.

Anyone thinking of putting up bat boxes would be well-advised to take advice from their local Bat Group. A little experience and foresight in choosing the right boxes and positioning them correctly will make a big difference to their success...or otherwise.

Advice from the Bat Conservation Trust: http://www.bats.org.uk/helpline/documents/Batboxes-yourquestionsanswered.pdf

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