The harbingers of spring, heralding bat surveys

In spring each year I, like most bat-workers champ at the bit, waiting for the survey season to kick off in May. I can't resist looking at some of my favourite roosts, to see if any bats have arrived yet.  A couple of weeks ago I spent a fruitless evening watching the roof of our cottage, to see if any of our resident Common Pipistrelles had showed up yet - they hadn't. 

Last week Charlotte Meyer-Wilson and I visited one of our favourite Soprano Pipistrelle maternity roosts to see what was happening. In summer around 1,000 bats occupy this roost, but we were happy to see 13, especially as we were playing with an infra-red video camera, which allowed us to see into the roost entrance and watch the bats moving around and interacting, prior to emerging.

It's at this time of year that I watch out for what I think of as the 'harbingers of spring' - three common hedgerow plants that flower early and stand out, each one showing that the bat season is a little closer.

The first to appear is Coltsfoot (Tussilago farfara), its cheerful yellow flowers poking through the flattened mat of last year's dead vegetation. Its chunky, scaley stem is almost a reminder that it's tough and flowers before anything else round here.

After Coltsfoot, the next harbinger of spring is the Lesser Celandine (Ficaria verna), with shining petals and glossy cordate leaves. It's slightly scruffy flowers alwyas make me wonder if they were built on a Friday afternoon.

My third botanical harbinger of spring is Garlic Mustard (Alliaria petiolata). Following on from the other two, the speed at which their tall stems zoom up in every hedgerow is amazing, allowing them to flower and set seed before they’re overwhelmed by the mass of species that follow. 

When garlic mustard shows I know that within 1-2 weeks the hedgerows will, for a brief period, be awash with swaying white Garlic mustard flowers. And that means it's time for the bat survey season to start, which puts an even bigger smile on my face!

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The missed bat

I lean against the rough, damp bark and stare hard, waiting for it to show. Unseen, a pair of beady eyes peers from a crevice and waits for me to break my gaze. I stare on. The bat reverses and puts the kettle on – it can wait.

Duh-duh-duh-duh! I tense. Is it? Just a bat flying past. I lean back into my tree and laser into the building. Will. Not. Miss. It. But what if it’s not there? I sigh, but stare on.

Suddenly, there it is! Big! Too big. Just a starling. I shift my feet, trying to get comfortable. The little eyes peer out from under a slate. Or is it the wall-head? Or flashing? Or a mortar gap? It waits. I wait.

An itch. I wriggle my nose, but no good. A sneeze. The eyes gleam and it hurtles out. “Duh-duh-duh-duh!” The detector speaks and I’ve missed it. The bat circles behind me, sniggering. It’s played the game and won. Again.

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Bat survey characters - Claymores, beach-balls and giggle twins.

There is something amazing about the people who choose to do bat surveys. The hours are antisocial, the work tiring, the locals challenging and the filling station food abominable, but the real hard core bat surveyors keep coming back for more, and I have encountered some genuine characters - from the charming to the terrifying, with throughly peculiar and absolutely astonishing likely to turn up as well. So, I feel it is past time to celebrate some of them (Names have been changed to protect the very guilty).

Beach-ball Barbara used to turn up early for surveys, to allow time for her special pre-survey ritual. Barbara had a problem with the cold. It wasn’t so much that she didn’t like the cold, it was that she had never experienced what she considered to be warmth and so the pursuit of insulation was an all-pervading occupation for her.

Before each survey Barbara would stand at the boot of her car and pull on a couple of pairs of fleece-lined over-trousers, before starting on the main act. She would put on fleece after fleece, starting with some figure-hugging ones, moving onto some regular fleeces and then slowly building up the layers and sizes until, some time later, she finally pulled an XXL size one over the top of enough fleeces to equip a fair-sized flock of sheep.

By this point Barbara’s shape had changed from regular human to something roughly planet-shaped. Finally satisfied that she had done all that could be done she would add several woolly hats and waddle across to give her standard greeting of “Bit nippy tonight, isn’t it?” As I was more than likely wearing a T-shirt it was usually hard to know how to reply to that.

“Mad” Angus had an amazing ability to confound perspective. Though I’m sure he was a sensible height he seemed to be around 8 feet tall. His uncontrollable shock of ginger hair, sun-reddened complexion and burly figure, when allied to a good Scots brogue, created an overall impression of someone who might at any moment choose to come hurtling down a hillside towards you, clad in just a plaid, brandishing a claymore and howling gaelic war-cries.

In fact Angus was the most polite and gentle person you could hope to meet, but “crazy eight-foot highlander” was how he looked and so it was always my intention to push him towards any trouble on a survey, in the expectation that the bad guys would take one look at Angus and choose to slink rapidly back under their flat stones of choice, allowing us to complete our bat survey in peace.

The giggle twins were not in fact twins, but I always found it convenient to think of them as such. At some point in the dim and distant past Suzie and Alison had met on a training course and bonded, forming the sort of close, almost symbiotic friendship that women seem to be so much better at than us men.

I could never understand why they didn’t appear to socialise together, but it seemed like bat surveys did the trick for them. So, the preparation for every survey would commence with Suzie and Alison, both screeching with delight to see their long-lost friend (despite having done a survey together yesterday) and dancing around each other, both talking nineteen to the dozen as each attempted to update the other about every tiny detail of their lives since they last met. How either heard a word of what the other was saying is beyond me, but the whole ritual seemed to make them both happy and it was certainly entertaining to watch.

Jim the Grinch was about as emotionally distanced from Suzie and Alison as it was possible to be. I could never understand why he did bat surveys, since he gave every impression of hating bats, bat surveys, bat detectors and in fact absolutely everything connected with the whole process.

I’m fairly certain Jim had long since forgotten the technique for smiling, and his pebble-like eyes glowered out from under a permanent frown and Compo hat. He kept a soggy cigarette permanently stuck to his bottom lip and would occasionally make perfunctory attempts to re-light it, whilst complaining bitterly about anything and everything. The bat detector was deaf, the batteries were no good; the site was too muddy; the weather looked poor, the younger surveyors knew nothing, and on and on he would go. At least I think he did. I had long ago perfected the technique of allowing him five gripes and then switching off.

Graham, the fabulous baking boy was pretty average as a bat surveyor, but sometimes other things matter more and his home-baking was simply superlative. You could guarantee that he would turn up to each survey, dripping in tupperware, and would start handing out his delicious largesse to anyone who came within range. In fact, he was very useful when a client turned up on a survey, as I could count on him to keep them entertained with sticky buns or triple-choc-chip muffins (yes, they are a thing, and utterly delicious), whilst the rest of us got on with the survey.

Some years ago I instituted a rule known as the "donut survey rule". This dictates that any bat survey which takes place in an urban location, with low bat activity, is officially designated a "donut survey" and the company provides donuts at the end. Graham took offence at Tesco's offering and took on this task, creating the most incredible sticky, gooey donuts you can imagine, so urban surveys suddenly became surprisingly popular. But in my view Graham's pièce de résistance was definitely the dawn survey pain au chocolat. I can think of no better way to end a dawn survey in a concrete jungle than to bite into one of those meltingly delicious confections.

Keep checking back - I'll share some more of my favourite bat survey characters soon.

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The ups and downs of leading bat walks - Guest Blog by Graeme Wilson

I asked my old friend, 'The King of Bat Walks', Graeme Wilson, to pen a guest blog. Graeme is the most prolific leader of public bat walks I have ever come across, doing dozens of them most years and having a major positive impact on public perceptions of bats across the Lothians and Borders.

Hi! This isn’t David. My name is Graeme Wilson and I am a freelance ecologist and wildlife educator. David asked me if I would be a guest blogger and of course I said yes! On the subject of what he wanted me to write about he said, “Bat-related would be good, but… could be something else - whatever you like.” That leaves me with quite a lot of options!

I could write about my year long project, called 'My Wildlife Year', where I am editing together a video every week covering what I’ve been up to but I won’t. (Don’t let that stop you looking for 'My Wildlife Year' on Facebook, Twitter, Instagram and YouTube though!)

I could write about the community wildlife project I am starting up that is hopefully going to get those that live in my local patch in and around Denholm in the Scottish Borders learning about and caring for wildlife, but I won’t.

I thought instead I’d write about the ups and downs of leading bat walks. A bat walk, if you have never been on one, involves someone talking about bats for a wee while and then you having the opportunity to listen to bats on bat detectors, as well as seeing them flying around.

I attended my first bat walk over 20 years ago and unfortunately the person that had been brought in to lead it was not very good, though I was really impressed by hearing bats for the first time. The bat walk leader’s knowledge was passable, but he lacked passion and the kids that attended it were not left enthused. I am trying not to be overcritical as it is not easy to stand in front of an audience and talk on a subject that is not your speciality. The person that had organised the bat walk told me I was leading the next one!. A year later he got me to lead my first bat walk. That was my first of many.

Over the years I have refined my bat walks and learnt to aim at the right level for my audience and try to inject a bit of humour where I can as well as teaching people to love and respect bats. I now lead between 20-30 bat walks a year, or I was up to Covid coming along, Though I still managed 5 socially distanced bat walks in late summer/early autumn 2020, when restrictions had eased.

Each time I lead a bat walk, I still get nervous. I know my subject and I am confident that I can answer most questions, though occasionally someone will ask a question that is unexpected and I don’t know the answer to. There is nothing wrong in that situation with taking their details and going to research the answer to send to them. What makes me nervous is questions like how many people are going to turn up? And are the bats going to show?

The numbers turning up can vary so much. I prefer to run bat walks that are pre-booked so that you know the size of your audience, but one organisation I lead walks for advertises them as events to just come along to with no booking. I don’t blame them for advertising like that, as it is all down to their funding. They get grants based on head counts at events rather than the number of events or the quality of the events. I think the smallest number I have had turn up at one of these bat walks for this organisation is 2 but that was a bit of a wet and windy night, though we still had a Soprano Pipistrelle or two turn up!

Technically, I did once turn up to lead a bat walk for the same organisation and no one turned up. It was actually for a group of adults with a learning disability that were supposed to be picked up by a minibus and brought to site but the minibus driver never appeared so walk was cancelled. Even though I got paid whatever happened, I felt disappointed for all those that had been sitting waiting to be picked up and looking forward to a bat walk only for no one to collect them.

At the other end of the scale, I was booked to lead a bat walk for the same organisation in Edinburgh. We were meeting on a grassy area next to a walkway/cycle path. I got there with a couple of minutes to spare, but there was no one there! I was about to call the person who was organising it when she called me. I explained I had just arrived and she replied, “Graeme, can you see the crowd of people walking away from you in the tunnel?” I replied I could. “Well, I am at the front of it leading them to a park!” So many had turned up there was not room for them all so we had to move to a local park that was big enough to accommodate a crowd over 200!

How do you lead a bat walk with 200 people, you may wonder? Well, the answer is with difficulty! It usually (yes, usually, as I have led several bat walks of between 100-200+) involves me standing on a bench and projecting my voice, which is just a polite way of saying I shout! If I suspect it is going to be a bat walk with high double figures or even triple figures, I never book another bat walk for the following night to give my voice time to recover.

Bat walks with high numbers like that involve very little walking. It just isn’t possible to keep everyone together, so we usually just stay in one locality. The bat walk I referred to earlier was supposed to involve walking away from the park, along the walkway/cycle path. However, as there were so many we just stayed in the park and after I had done my talky bit people could explore the park with bat detectors. Fortunately, we had quite a few, but it was still one between several people. Being in one location like that has some benefits, such as it is easy for people to find me to ask individual questions.

I have to admit, I prefer a much smaller group. Not just because it is easier on my vocal chords, but because I feel those attending a bat walk that has limited numbers get a much better experience. That isn’t to say that I haven’t had really positive feedback from people that have attended one of the massive bat walks I have led but it is all relative. A smaller group get more access to me and it can be a bat detector each or one between two or three depending on the size of group and the number of detectors available.

Giving out bat detectors to those attending is always a risk, but only once has one disappeared, never to be seen again! One went home with someone by accident but its return was arranged and another time one disappeared but a quiet word with the right people and they soon returned it.

One question I often get asked on bat walks is what is the best bat detector to get? I always recommend the Magenta Bat 4 which retails at around £60-65. It is cheap, robust, and is a great detector. There is the Magenta Bat 5 which is about £30 dearer and is exactly the same as the Bat 4, except it has a big digital display rather than a dial with frequencies written on it. The extra expense is only worth it if you have problems reading small print.

The other thing I regularly recommend purchasing is the Field Studies Council’s foldout Guide to British Bats. It costs £3.30 so doesn’t break the bank and has a lot of useful info including flight patterns, description of echolocation calls and peak frequencies, as well as frequency ranges.

As I mentioned earlier, Covid affected the number of bat walks I led last year and who knows what it will mean this year! However, I have decided not to wait and see if I will lead bat walks later in the year but have led them now. How can I do that, I hear you ask! Or I imagine I hear you asking! Well, I have run virtual bat walks on Zoom.

This has involved me recording various bits over a few weeks and editing it all together into some sort of coherent order. One thing I have been able to include is some footage and photos of some bats I have rescued over the years, which is obviously not possible at an in person bat walk. I’ve only done one so far and have made a couple of tweaks for the next couple I have in the pipeline. Maybe I’ll see you at one of my future bat walks, either in person or online.

I post info about bat walks I am leading, as well as other public events and training workshops I lead on my social media: Facebook, Twitter & Instagram @graemebwilson

Graeme and I have collaborated on many wildlife projects and organisations over the years. He can turn his hand to identification of almost any species group and is a brilliant wildlife educator, but I think the highlight has to be Rona and my wedding, when Graeme made a hilariously witty speech in his role as 'Spokesman for the Best Dog'! 

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Goliath II - harp trapping bats, taken to extremes

Over the years, one subject in this blog that has gained a lot of interest is the building and use of harp traps. Back in 2008 I described building a trap with permanently stretched strings, slightly smaller than the commercially available traps (see The kitchen table harp trap). Since then I've had more queries about that than about all the other posts I've written combined.

The ever-reliable 'Kitchen Table Harp Trap'

I've also written about several occasions when we put the kitchen table harp trap into use after building it. I'm happy to say that it has been a very successful trap and has caught many hundreds of bats for us. Well over a decade later, it is still in regular use and I have only ever had to replace a handful of strings. 

I've written three posts about how it fared in practice:

•  A bat in the hand  (May 2008)
•  Happy harp trapping  (August 2008)
•  Swarming bats and shivering bat-workers (March 2011)

In 2014 I started experimenting with larger harp traps, inspired by Merlin Tuttle's original harp trap and I described a massive one I built, using a similar technique to the kitchen table harp trap, but on a grand scale (Goliath - the Daddy of harp traps, March 2014).

Although Goliath was successful in catching bats, it had a couple of major draw-backs. When assembled, a post obstructed the centre of the trap. This wasn't part of the original design, but was necessary to resist the intense power of hundreds of strings hauling the top and bottom bars together. But a bigger issue was transport. As I built it with a light yet strong aluminium alloy frame, it was light enough to move about, but because of its size it had to be transported on a car roof rack, making the strings vulnerable to tree branches catching and ripping them in transit. Storage of the trap was a bit of a challenge too! 

After a couple of seasons, I reluctantly decided that permanently stretched strings weren't really viable for such a gigantic trap. I went back to the drawing board and the eventual result was Goliath II.

The Goliath II harp trap before I adjusted the height of the bag. The immense pull of hundreds of taut nylon lines causes the slight bow in the top and bottom beams.

For Goliath II I used many of the parts from Goliath, converting it to a roll-up harp-trap, similar to the commercially built ones, but noticeably bigger at nearly five metres high. The bag is fairly shallow and, after shredding my fingers whilst sewing the canvas and sheet plastic for the "Kitchen Table Harp Trap" bag, for Goliath II I wimped out and made a temporary bag out of lighter material, with seams closed with heavy duty tape. This has been so successful that I've never seen the need to update it.

You get a sense of the size of Goliath II, when you see it indoors. I set it up inside so that I could stretch and tie the hundreds of nylon lines with fiddly double-grinner knots whilst they're under tension. Trust me - this job is best avoided.

A later addition was two arms to support the trap bag, lifting it so that the edges were above the bottom of the trap, after we'd lost a few bats through that gap. The bag sits just above the ground, different to most traps. This has the double benefit of making it less of a visible obstruction to bats in free flight than traps on longer legs and removes the need to block the space between the legs to prevent bats from flying under it. Occasionally we have also attached vertical arms to create a rubble net obstruction above the trap, to funnel higher-flying bats through it.

Goliath II, during erection, showing a mesh extension at the top.

There's a knack to rolling and unrolling a regular harp trap without catching or tangling any of the strings or getting them wrapped around the ends. Doing it with Goliath II is an even bigger challenge, but with practice it became easier. Trap strings have to be unrolled and kept under tension at the same time - letting them become loose is a recipe for chaos and damage. Once they're fully unrolled they are stretched to full height by adjusting telescoping poles at each side, aiming to get the strings to where they make that reassuring "plink" noise when you pluck them, showing that they're just right!

Putting the trap together in open space prior to tensioning. The triangular bipod on the left is one of two which rotate as we erect the trap, allowing it to rise, whilst keeping its feet on the ground.

Because of its height, the trap has to be held in place vertically by two angled guy-ropes, from the top corners to stout pegs in the ground. Raising it has a definite hint of Amish barn-raising about it (if you don't know what I mean, you really must watch the 1985 film "Witness"). It's relatively easily done by a team of four or five, but two people who know exactly what they're doing can manage, with the help of a couple of pulleys attached to the pegs. The four short legs stay on the ground, rotating around the base of the trap as it is pulled vertical with the guy-ropes.

Doing the reverse procedure in the dark has its challenges. Here the tension is being released, prior to rolling up each side.

A side view of the trap fully extended and erected, though this picture doesn't show the arms, which were later added to lift the bag.

One of the leg bipods, showing the bearing which allows the trap to rotate into position and the arms, which were later added to support the bag.

The trap has been very successful over the years since I built it and has many captured bats to its credit. One of its first outings was to a Northumberland castle, where it was used to capture Daubenton's bats emerging from an open-ended cellar. The space was so large that we had to use rubble-netting to surround the trap, but it caught a substantial proportion of the merging bats, as well as several foraging Pipistrelles. Since then it's had many outings to catch bats in free flight, which is what it was really designed for.

Goliath II, seeing service as an emergence trap at a Northumberland castle, surrounded by rubble-netting, to funnel bats into the trap.

Here Goliath II is in use for its intended purpose - catching free-flying bats.

Like all bat-workers, I'm looking forward to returning (hopefully soon) to catching and handling bats within some of our research projects. I just hope that, after a year's absence, we can recall how to put Goliath II together. I'm sure we'll figure it out!

Keep coming back and soon I'll tell you about another addition to our stable of harp traps.

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Further news from the gods of bat-work

I recently wrote about the gods of bat-work - small, mischievous god-lets, who entertain themselves by making our lives complicated (Ignore the gods of bat-work at your peril). So many people seemed to enjoy discovering the truth behind those niggles and problems in their professional lives that I thought I'd tell you a little more about them.

Have you ever wondered what happens to a bat ecologist who shrugs off their mortal coil? As with all things, the gods of bat-work have a part to play in this, and it may surprise you to hear that there are close parallels with the Norse world. When a viking warrior died in battle, a beautiful, shining winged valkyrie would bear him off to Valhalla, the feasting-hall of the Norse gods. In our case, it's more likely to be a couple of tatty Pipistrelles who owe you a favour, but it's the thought that counts.

On arriving at the chiropteran feasting-hall, one or two differences between it and Valhalla may become apparent. Like the vikings, we will spend the rest of our days feasting with the gods, but we'll do it in a more appropriate manner. The vikings would sit at their feasting-benches, imbibing great foaming tankards of ale and goblets of mead, whereas for us of course it will be luke-warm cups of Costa coffee and out-of-date cans of Red Bull. You see, the gods of bat-work would like us to feel at home after we switch off our detector for the last time.

Not for us the roasted sucking-pig or great sides of beef, whilst talking of battles and wars - that would be simply wrong. Until the end of days we shall feast on service-station sandwiches, tupperware boxes of left-overs and many strange Ginsters products, whilst arguing yet again about whether that bat three years ago really was a Barbastelle...

There will also be some strange burgers made of compressed midges and there'll be meal-worms, served squeezed-out or not, according to taste. After all, this is the feasting-hall of the bat-gods, and their delicacies can't possibly taste worse than our filling-station menu, can they?

But who will serve this largesse to us? For the vikings, that was easy. If they didn't have enough serving-wenches, they could simply capture some more on the next raid. Clearly, for us, in the 2020s that is not appropriate, especially as professional ecology has more women than men, most of whom are a better fit for the role of feasting shield-maiden than serving-slave. So the gods of bat-work, recognising this problem, have found a solution. Unscrupulous developers who have destroyed bat roosts without a license will serve the feasts. After all, until recently the fines for this were so small that they must surely be due further punishment in the afterlife? To add to their punishment they might be shaved, oiled and forced to wear the sort of leather gear that Holywood thinks Roman slaves wore, but that decision is probably best left to the shield-maidens.

So, once we've partaken of the food and drink that the bat-gods know we love (after all, we eat and drink so much of it?) what entertainment will await us in this chiropteran feasting-hall? Viking warriors would spend their days at Valhalla re-fighting their favourite battles. For us it will clearly be re-runs of our favourite surveys - you know, the ones where it definitely was a Barbastelle, and you got a clear view of it foraging. Or will it? The gods of bat-work cannot resist a little mischief and think perhaps we would prefer to spend long hours analysing thousands upon thousands of bat calls, whilst desperately short of sleep. After all, this is how we spend our lives, isn't it?

At least spending the rest of our days in this batty Valhalla will give us the chance to meet and feast with some of the lesser-known bat-gods.

• You may encounter the bat-god of creaking timber, who amuses himself by making old beams creak and groan, just as you put your weight on them. You know they're sound, but that little bat-god voice in the back of your head suggests otherwise.
• You'll meet the bat-god of thermos-hammering, who can take the stoutest of coffee flasks and shatter them. He's also branched out into making unbreakable flasks utterly useless for keeping your coffee warm.
• The bat-god of bugs might introduce himself and, with great amusement, tell you that all those caddisflies you swallowed during a survey last year were his pets, as was the Elephant Hawk-moth that head-butted you.
• A sudden squeaky-squawky kind of undescribable sound behind you will herald the bat-god of unidentifiable ultrasound (also known as "Middleton's Nemesis").
• Meanwhile, the bat-god of SD cards will amuse himself in the background, playing air-hockey with a pile of SD cards. But at least, from the Valhalla of the bat-gods, you'll be able to see them being snuck back into your former colleagues' equipment. And, as you watch the cards fail on a survey and see the anguish that causes, maybe you'll experience just a little of how much fun it is to be a bat-god.

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