Chirps in the noise - the hunt for a missing bat

“Chirp…chirp…chirp.” I’m sitting on a clump of grass, with the farms and villages of the Dead burn valley laid out in front of me, one or two lights beginning to come on as the light begins to fail. “Chirp…chirp…chirp.” I’m holding a directional yagi antenna, pointed towards some farm buildings below me and on my lap sits a strongly-built radio receiver. The gain is set to maximum and the signal strength meter bounces to the right, in time with each sound. 

This is a pleasantly relaxing moment, watching the world winding down and waiting for my target to show its face. Before long I will leap into action, but for now I can just wait and relax.

A walk-in-talkie clipped to my jacket crackles. “Nothing yet.” says a remote voice. 400 feet below me and about half a kilometer as the crow flies, a couple of young ecologists with similar equipment are standing in the farmyard, waiting for a Common pipistrelle to emerge from her roost. We’ve been following this bat for several nights and are starting to build a picture of her nightly behavior. But a couple of times she has simply disappeared from the area where she spends most of her time and we haven’t yet succeeded in finding her before she returns. But tonight we’re ready for her.

Glued to the fur on her back with a special rubbery glue is a minuscule radio transmitter, half the size of my little fingernail, it’s hair-thin wire antenna trailing over her tail. It’s tiny battery produces a tiny radio signal - a steady series of chirps we can only hear if there is nothing between us and her. Not too hard perhaps in the flatlands of East Anglia, but here in the southern uplands of Scotland it’s an exciting challenge - every fold in the land is capable of blocking the signal, so that we hear nothing.

 

The radio crackles again. “She’s out.” The chase is on. Almost immediately the sound changes and the strength of the chirps vary, as she flies round the farm buildings, the old sandstone walls attenuating the signal. I slowly move the antenna to the left a few degrees and check the signal. It’s louder. To the right again. It’s quieter. Constant adjustments and checks allow me to keep track of her. The team below are doing the same and we constantly share compass bearings. She is roughly where they intersect on the map. They give chase, but my tack is to monitor from my hill-top eyrie and help them fill the gap.

True to form, after forty minutes of foraging around the tree-lined margins of a large pig-field she suddenly makes a move. I’m alerted by the fleet-footed team below and a moment later “we’ve lost her.” But I still have a faint signal for another few seconds before she disappears and I get that all-important bearing. A check of the contours on the Ordnance survey map reveal a fold  in the land in that direction, with a tree-lined pond. I vector the team onto it and off they go. Ten minutes later the walk-in-talkie crackles with a triumphant shout. “Got her!”

 

I sit back onto my comfy clump of grass, satisfied with another piece fitted into the jigsaw of this bat’s behaviour. With a sigh of satisfaction I change the frequency of the detector, to see what’s happening with the bat that team two are following.

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In the bat-caves with a camera

People are often surprised to discover that my first degree was in medieval history, rather than ecology. As it happens I'm also qualified to decode Morse code, carry out psychometric testing and chair legal tribunals, but none of these are relevant either and just show how my career wandered about before I found my forte! But the history of science can be an intriguing cross-over - how did our knowledge of bats and ecology arrive where it is now and who did the ground-work for us?

Back in 2009 I wrote a couple of articles on this subject: The 'diffusion of useful knowldge' and An 1892 bat-worker. I recently came across another article from 1898, written by T.A.Coward in a magazine called "Wide World", describing efforts by he and his friend MR R. Newstead of Chester to photograph bats in various British caves, at a time when photography hadn't progressed far from the formal staged photographs of the Victorian era.

Reading articles of this vintage can be startling at times. Back then natural history was not the conservation movement it now is. Much of the damage we are now desperately trying to repair had yet to be done to the natural world by the technological and chemical advances of the twentieth century and wildlife was seen as an abundant resource, to be drawn from freely in order to study it. Our modern views on the humane treatment of animals were also in their infancy. We have to grit our teeth and set these things aside if we want to listen to the voices of our forebears in the light of the world they lived in at the time.

Despite that, it's possible to see that many of the problems we face today were just as problematic to the Victorian natural historian:

"...the naturalist thinks little of experiences like these, and if his clothes are dirty and his hair is full of mud as he walks home, looking like a bricklayer's labourer, what does it matter...?"

That sounds like many a hibernaculum survey I have done. He goes one to remind us that he is talking from one and a quarter centuries ago when he continues...

"...if in his pocket he has his treasures, and when he arrives he will be able to examine or photograph his little friend the bat."

Oops. He also mentions a Daubenton's Bat he "had wounded", swimming itself to shore, which makes uncomfortable reading for us today, as does hearing that Coward:

"...once received a large number of these bats from the North of Scotland."

A powerful comparison with today can be seen, when he talks about gaining access to bats, to study them:

"We have found the best way to obtain them alive is to search for them in their native caves... We have scrambled about in the semi-darkness lit only by the guttering, greasy candles, our boots sticking in the wet clay..."

Hand-held bat detectors were almost a century away, let alone infra-red cameras. Even the electric torch was about twenty years away. Whatever we may think about taking bats home to photograph (whether dead or alive), there's no doubt that this was hard-core work! 

Newstead also took pictures of bats in situ in caves, though arguably the magnesium flares he had to use for illumination must have impacted on the poor subject bats. Nonetheless, it's exciting to see his photographs, which must surely be some of the earliest pictures of bats in their roosts. However, some of his portrait pictures are very definitely of dead and possibly taxidermied specimens!

I've written before about how weird occurances and bat-work seem to go hand-in-hand (Bat surveys - where odd stuff is normal, There's nowt so queer as folk and What is it about bat surveys?) It seems things was no different in 1898:

"...we entered an old lead working in Derbyshire, and just as we were striking a light (presumably to light a candle!) we were suddenly backed into by a cow that had been sheltering from the hot sun in the cool recesses of the cave."

Coward's love of bats might not always be apparent in his approach to studying them, but it certainly in in his prose:

"The Whiskered bat, a neat little fellow..."

"The Pipistrelle, or Flittermouse, is a pocket edition of the Noctule."

"Perhaps the quaintest of our commoner species is the Long-eared bat...as it turns its beady little eyes towards us, twitching its great ears, it seems to be asking who it is that is so rudely disturbing it."

Early naturalists like Coward and Newstead helped to build the early foundation towards an understanding of bats that we are still building and though their methods are alien to us today, we still owe them a debt. Coward wasn't shy of using his magazine article to address some anti-bat prejudices that seem very familar today:

"...wherever we go we are told stories of the "nasty things" flying in through windows, atttacted to sheets hanging up to dry, or getting entangled in ladies' hair. We only know they will never fly through windows, they never come when we hang up sheets and they take great care to keep away, not only from our heads, but well out of arms reach."

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Super-speedy-cheap bat surveys!

Roll up, roll up people, get them while they’re hot,

Super-speedy-cheap surveys, with a detector that I’ve got.

It’s just a cheap detector, neither broad-band nor much use,

But the guidelines are too complex, so I play fast and loose.

My customers know no better, of standards they know not,

As long as I’m cheap and cheerful and the council accept the lot.

The council had an ecologist, laid off due to cuts,

So now I hardly need to lie, in my reports from ‘Comic Cuts’. 

This building needs six people, but we are only three:

My granny, Fred from down the pub and little ‘bat expert’ me.

The client will not notice, so in my report I’ll lie,

And say that there were eight of us, well-equipped and spry.

Granny keeps on wandering and often needs a pee,

And Fred knows nowt about bats, but bull-sh*ts as good as me.

I’ve two more surveys on tonight, so they I must invent,

For we are Super-speedy-cheap, for clients heaven-sent.

Of course I have a license - a really nice one too,

Signed off thirty years ago, by a mate, works down the zoo.

They tell me conservation law has changed in all that time,

It matters not - I always turn, a blind eye to wildlife crime.

We very rarely find a roost, in fact I prefer not to,

It makes my clients happier and keeps us speedy too.

When Licensing’s required, you won’t see me for dust,

For fear of being found out and maybe going bust.

So I’ll keep on doing what I do, and getting away with it,

Doing surveys cheap and quick, but honestly quite sh*t.

I’m hoping council funding continues to be pathetic,

‘Cos neither them, nor SNCOs have time to see I’m at it.

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The forthcoming Anabat Chorus - first impressions

Fifteen years ago, if you wanted to do passive monitoring of bats you had three options - the proven and dependable sandwich-box-shrouded Anabat SD1, with it's ZC recording system (seems clunky now, but was heaven-sent in those days of memory-deprivation and snail-like computers) or the Songmeter SM2 from the then new kids on the block, Wildlife Acoustics. Option three was to cobble up some kind of half-baked system with a basic detector plugged into a dictaphone and plenty of us dabbled with that sort of thing! Today  however, the marketplace is full of options and new models keep trickling onto the market.

Wildlife Acoustics recently launched the Songmeter Mini and I'll say more about that in another post, but there is a clear move towards lower-cost passive monitoring machines, possibly in response to the development of the incredibly low-cost Audiomoth. When you can buy a passive detector for thirty quid (extra for the polythene bag to hang it in!) then £1300 or more seems excessive. However, for professional work the Audiomoth seems an uncertain option, with too much geekery involved. Though that will probably change in time, it creates an opening for the manufacturers to slide in new mid-range passive detectors, drawing on their experience and reliability. 

The new Anabat Chorus

Andrew Dobson of Titley Scientific was kind enough to lend me a beta model of their forthcoming new machine, the Anabat Chorus. I've long been quite keen on Anabat equipment - it's not perfect (what is?), but Titley tend to listen carefully to customers and build on what they learn from each model. The Chorus is a good example. At first sight the case looks similar to the Swift and Express models, both of which are a pig to open, as the latches are incredibly tight - a necessity, to seal the case against moisture ingress. The solution is rather elegant - a large lever-type arrangement applies one of those first physics lessons we learned at school and makes opening and sealing the case much easier. There are also pierced flanges top and bottom, increasing the options for attaching the case to a substrate, especially useful for longer-term installations.

Inside the case, at first sight it seems similar to the Swift and has most of the functionality, but instead of the sexy (and costly) touch-screen, the screen is more basic, with up/down/left/right buttons. The battery case takes four AA batteries, but with Eneloops (the rechargeables of the gods), that should give many weeks of recording, in fact Titley claim 40 nights is possible. And they've retained the easily accessible back-up battery, so you can change it yourself when needed. As with most equipment nowadays, GPS is built-in, ensuring that that accurate sunset and sunset times can be depended on. There's also a temperature sensor, though personally, I rarely trust the data from in-built sensors. The detector is not always in the best location to get sensible data, so I tend to use a separate temperature datalogger in a shady spot nearby.

The interior of the machine and the controls - essentially a budget version of the Swift controls, but without losing anything vital that I could find

Rear view, showing the pierced mounting flanges and the lever arrangement, for opening the case with breaking a finger

In use, I found it to function exactly as expected, with similar funtionality to the Swift, using the control panel to select simpler timing options or a new software package to allow custom settings. As with the Swift, you can record ultrasound as .zc or.wav. There was a little distortion in the recordings, though this was probably due to reflections off the case. You can't use an extension lead with the microphone, as with the Swift, but Dean Thompson from Titley advises that there'll be an optional goose-neck extension to move it away from the case and reduce this effect. 

The optional microphone gooseneck

(photo copyright Titley Scientific)

I'm happy to say that they have retained that wonderfully simple crowd-pleaser, the little magnet on a string. This allows you to check the machine is functioning properly once it's in position - rarely essential, but massively reassuring before you walk away, trusting that when you return in three weeks time the detector will have recorded as expected.

Considering that the Chorus will retail at £595 +VAT I was a bit bemused as to where the savings had been made, by comparison to the rather pricey Swift (currently £1194 + VAT from NHBS).  According to Dean, the main differences are:

• You can't use an extension mic lead (the gooseneck will cost extra)
• The machine can only use 4 AA batteries, unlike the choice of 4 or 8 with the Swift.
• It only has one memory card slot, instead of two (but with the massive capacity cards now available, that's hardly a problem).
• You can only record from one microphone at a time.

What's this I hear you ask? "One of two microphones"? The Chorus has an acoustic microphone as well as an ultrasonic one, giving you the chance to record birds, frogs, crickets or whatever else takes your fancy (for £200 less you;ll be able to get one with just the acoustic mic). It has the same ultrasonic microphone element as the Swift (though they're not interchangeable). 

One concern I have is that the microphones seem quite vulnerable, as they are attached to mouldings on the case. The Swift and Express come with excellent protective carry-cases, but apparently that won't be the case for the Swift, so I think a protective case to store and transport it will be an essential extra.

In this view you can see the two microphones, ultrasonic on the left, acoustic on the right.

Overall I was quite impressed with what we'll get for the price-point. I was also impressed that most of what has been removed to get the price down is unlikely to be missed much and that Titley have taken the opportunity to add some simple enhancements that improve the package. It's disappointing that the gooseneck microphone mount will be an additional cost over the basic price, but they are going to have Wildlife Acoustic's Songmeter Mini to compete with and I reckon that will be a fair fight. 

The machine I was trying out was a beta model, so the final product may be slightly different. And if you want a seriously techie appraisal you'll need to look elsewhere - my musings here are for those of us who want to actually use the machine, rather than devour the specifications! But if that floats your boat you can find the full specification on Titley's website: Anabat Chorus

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PS - the photos above show a foam sock on the ultrasonic mic, but it belongs on the acoustic mic (when I tested it, it was on the correct mic!)

The dawn survey dirge

I promised I wouldn't do this again.

I lied.

A particularly dismal dawn survey inspired me (is there such a thing as negative inspiration?) to write a Dawn survey dirge. Can you tell it's almost the end of the survey season and I'm flagging a bit?!

It's to be sung to the tune of 'When a felon's not engaged in his employment' from 'The Pirates of Penzance'. If you're not familiar with it, here's the original - YouTube

When the sun is not engaged in it's employment,
And the caffeine isn’t doing what it ought,
The pre-dawn chilliness, it feels hell-sent,
And you regret the Esso sandwich that you bought.

Our reluctance we with difficulty smother,
When dawn surveying duty’s to be done,
We must drag ourselves from one bed or another,
A bat-worker’s lot’s a really crappy one.

When dawn surveying duty’s to be done, to be done,
A bat-worker’s lot’s a really  crappy one, crappy one.
 
When the trip-hazard is in utter darkness hidden,
And a moth flies in your ear, causing stress,
Whilst mosquitos gnaw upon you most unbidden,
And your sweeties have become a soggy mess.

When your folding camp-chair under you has broken,
And rain-water, it is seeping in your boot,
Whilst your bat detector firmware won’t awaken,
And you fear your head-torch battery’s up the chute.

When dawn surveying duty’s to be done, to be done,
A bat-worker’s lot’s a really  crappy one, crappy one.

When I inflicted 'The bat identification song' upon the world several mischievous people suggested I should post a video of myself singing it, or even perform it at their bat group or a conference. There are several problems with this, chiefly that my singing voice resembles a part-strangled cat having its genitals mangled whilst gargling. But feel free to step in - YouTube, fame and fortune awaits the brave!

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