An attic search

Creaking joists. Dusty cobwebs sweep my face. Trying to be silent whilst hunched and balanced. Progress is slow as I sweep my torch carefully.

Amongst the dust clogging my nostrils comes the hint of a different odour: organic, with a tang of urine. The ‘nose’ of bats. I cast around like a bloodhound, searching for the source.

Mouse droppings scattered about, like tiny bricks. Searching for the crumbling ones. Dodging the protruding nails.

The hint of a scratch? Maybe a scuffle? Edge closer, dimming the torch. Peer round a rafter. Scritch-scratch. There! A dozen faces stare back, ears erecting. Expressions like offended spinsters.

I slowly reverse. Stiff, dusty and delighted.

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"I know there aren't any bats..."

In my work I meet many bat roost owners, varying in attitude towards "their" bats from delighted to appalled and all points in between. I also encounter many people who are commissioning a bat survey because they have been obliged to do so. Often in the UK this occurs when someone applies to their local authority for planning consent to carry out work on a building. The law requires the local authority to consider protected species, so if there is any possibility for a bat roost to be present a bat survey must be carried out. "I know there aren't any bats there, but we have to have a survey" is often the client's opening gambit. It's not an unreasonable attitude: what little most people know about bats leads them to expect them to be highly visible, extremely rare and likely to roost in caves or gothic castles. Against that background it seems insane for a local authority to request a bat survey of a three bedroom suburban house, a 1970's primary school or a city centre council flat. Yet I and my colleagues frequently come across bat roosts in buildings like these.

This modern primary school is home to 280 Soprano Pipistrelles. They roost alongside the main entrance and most people think the noise is made by nesting birds.

Part of the problem is one of perception - bats are rare, that's why they're protected. Yet some bat species are very common. Here in central Scotland Soprano and Common Pipistrelles and Daubenton's Bats are all common, but have the same level of protection as rarities such as Whiskered Bats or Nathusius' Pipistrelles. Rarity isn't the sole reason for protection - vulnerability is a key issue. Our commonest species (in central Scotland), the Soprano Pipistrelle gather in their hundreds and even thousands to breed. The destruction of one of these roosts could harm the species over a large area. Bats reproduce very slowly - a single female will often only have one offspring in a good year and the need to gain weight swiftly in order to survive hibernation means that many do not survive. Thus bats are usually slow to recover from set-backs. Reducing prey availability caused by pesticides, illegal roost destruction through prejudice and stupidity and a host of other factors all combine to make legal protection essential.

Another factor in the misconception is the expectation that bats are visible in their roosts. We have Hollywood to thank for that. People expect to glance inside an attic and see a host of bats hanging from the ceiling, with their wings wrapped around their bodies. In the case of Horseshoe Bats that genuinely is the case, though bats tend to be a great deal smaller than they appear to be when in flight. Most other bat species in the UK roost in holes or crevices of one type or another, meaning that when they roost in buildings they are less likely to be visible to the uninitiated. Not long ago I surveyed a farm, the owner of which insisted there were no bats around his farm. Not only were there three species of bats roosting in his farm, there was a colony of about 80 Common Pipistrelles roosting alongside his bedroom window.

This colony of Brown Long-eared Bats are tucked into a crevice between two roof beams. If disturbed they tend to move deeper into the crevice, out of sight.

I'm not sure where the popular conception that bats only roost in old buildings comes from. It's certainly true that large country mansions and castles usually do contain bat roosts, but this often has as much to do with the presence of undisturbed spaces and the maturity of surrounding habitat as anything else. Modern house builders are surprisingly good at including loose-fitting fascia boards, poorly attached flashing and many other features which bats find to their liking and it is usually in modern buildings that people are particularly surprised to find bats.

Not a building which fits with the popular vision of a building used by roosting bats, but 800 Soprano Pipistrelles roost under the slates of this house every summer.

I have no doubt that there are many buildings around the country containing bat roosts that the owners are unaware of. Either they don't notice the signs or don't recognise them for what they are. Two years ago I spent a couple of weeks flying (when I'm not working with bats I fly gliders) from an airfield in Leicestershire. The club house there is a single-storey, L-shaped building about five years old. In the shelter of the L-shape are comfy tables and chairs, accessible from the bar. It's a nice place to sit on a summer evening and is well-used by club members. I had only been there a couple of days when I realised that a colony of Common Pipistrelles were roosting  at the wall-head alongside these tables. Each evening as the sun started to go down around ten bats would emerge and fly through the group of people who were sitting drinking and chatting. Nobody ever noticed them! I suspect people occasionally glimpsed a bat and assumed it was a songbird. The club management were entirely unaware of the presence of a bat roost in their recently-build clubhouse. If they applied for planning permission to change it and were asked for a bat survey I expect they would be astonished and annoyed at being asked to commission a bat survey...

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Memories of Summer Bats

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

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

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

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

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

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

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

My website: www.plecotus.co.uk

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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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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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/