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

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!

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

Contact me: http://www.blogger.com/blog@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.



My website: plecotus.co.uk
Contact me: mailto:blog@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

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

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

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