BatChat

Going Underground on a Hibernation Survey

January 20, 2021 Bat Conservation Trust Season 2 Episode 20
BatChat
Going Underground on a Hibernation Survey
Show Notes Transcript

S2E20 Steve joins Helen Ball and other members of Staffordshire Bat Group as they undertake a winter hibernation survey for the National Bat Monitoring Programme (NBMP). Recorded in February 2020 in the Staffordshire Peak District, they undertake the latest survey of disused lead mines searching for bats deep in torpor.

Helen reveals what it's like to undertake the survey (it's a VERY steep hillside!) and what sort of things you're likely to find in old mine adits. Apart from the bats - lots of bats - there's other wildlife down there too and the surveys have revealed just how important the site is for the bats of the Peak District.

Find out more about Staffordshire Bat Group:

The NBMP hibernation surveys: https://www.bats.org.uk/our-work/national-bat-monitoring-programme

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Steve Roe:

Hello and welcome to this week's Bat Chat from the Bat Conservation Trust. I'm Steve Roe, and this week we're in the Staffordshire Peak District. When I started doing that work at the age of 12, one of the first longterm surveys I got involved with was a hibernation survey with Staffordshire bat group. Historically, Staffordshire and Derbyshire back groups have had strong ties because we share the Peak District National Park and every winter we still undertake this particular survey together. Now this year, many bat workers are missing going underground as there is an unknown risk of passing the Coronavirus disease to bat populations. And so to prevent that happening, all surveys undertaken for the national bat monitoring programme have been cancelled this winter. So we hope that this episode will remind existing workers that one day we will get back out there and to any of you listeners who are thinking about joining your local bat group, or have yet to undertake hibernation surveys will recognise how fun surveys are and will encourage you to get involved with your local group and to contribute to important long term datasets. So last February before we had any idea of what was about to unfold and that we were headed for a national lockdown, we took the podcast recording kit along on last winter's survey resulting in what may well have been the first podcast to have been recorded inside a mine adit. Helen Ball is the survey leader. And we join her at the start of the day making the two and a half kilometre trek from the cars to the nature reserve where the survey happens in the Manifold Valley. So it's a Saturday in the middle of February. I'm currently walking through a very blowy windy field with members of both Derbyshire and Staffordshire group. Helen, what are we doing today?

Unknown:

Other than getting lost on a very steep hillside. We're carrying out an annual check and Monitoring Survey for bats that use a series of mine adits to overwinter in. And hibernate so we're doing counts of the numbers of bats we see and the species.

Steve Roe:

And where about's in the world are we?

Helen Ball:

We're in the best part of the world. We're in the Staffordshire Peak District in the limestone area in an area of the Peak District known as the white peak, and it's riddled with caves and mines. And lots of them we used by bats.

Steve Roe:

So how long has it been going on here?

Unknown:

The study's been going on for quite a long time since the very early 1970s. And as far as I know, it's one of the longest studied winter hibernation sites for bats probably in the country.

Steve Roe:

Who was doing it although back then then.

Unknown:

Well, initially, the adults were checked by Derek Yaldon. Derek was a local mammologist, very eminent, internationally known zoologist who studied mammals. And he moved to the Peak District on Manchester side and spent most of his weekend studying mammals of the Peak District including mountain hares, the Wallabies that live down at the roaches but also bats. And he used to come up to the mine adits here on a weekend with his dog and check the caves for bats as we're doing today. And who owns the site we're heading to today's nature reserve or there's a series of minor edits 11 In total, two of the biggest edits along the studies are on Staffordshire Wildlife Trust, Nature Reserve known as Castern wood. And it's a very beautiful reserve overlooking the river Manifold, which we're coming up to now. And you can sort of see it and dips away way down into the valley and there's no sunshine down the bottom. No, it were the top of the hills about 500 foot above the river. And what sort of bat species are we hoping to find and then what sort of numbers we're hoping to find five species so for the Myotis Daubenton's, Natterer's whiskered, and Brandt's and brown long-eared they all use the caves and mines here. numbers vary from year to you. And between the different mine adits. We can get anywhere between maybe 20 bats up to 50/60 and sometimes even higher.

Steve Roe:

How far is it to the first cave?

Unknown:

Oh, well, I don't know a few hundred metres. This one is probably the easiest to get to. But they all involve going down quite steep slopes So the tunnels we're walking long, I'm struggling to stand up straight. They're less than six feet tall and metre and a half wide. And as you can hear it's pretty echoey so Helen we've scrabbled down a rather steep hillside and we've come through a gated system why have some of the systems got gates off. As some of the systems have got gates on on the sites are visited more by members of the public. So it's to stop people going into the adits who may be are not really kitted out are aware of what dangers could lurk inside. They're all padlocked and the grilled and the grills are set in a way that bats can still fly in and out, it doesn't affect their use of the mine. I mean, we just found five or six bats before the grille is that unusual or expect to find more inside further inside the system. So in this adit, in particular, we often get a concentration of Natterer's bats, particularly and one or two long-eared near the entrance. I remember one year we found eleven just in cracks in the entrance before the grille. So there's usually a concentration of Natterer's and a few long-eared's near the entrance. And then as we get further in the bats will be spaced along. You get Daubenton's, whiskered, Brandt's, How long are the systems on average what are the rangees. So the adits all very, there's some that are maybe only 5, 10, 30 metres long. This one's 90 metres long, but the far end of it's blocked with stacked deads and collapses. Some of the longer adits here are to 250, nearly 300 metres long. ["there's a WAB here Kelly" is called out by a distant voice from surveyors ahead of Steve and Helen] So the guys in front of us are searching the walls, is there a particular method and what they're doing? Yes, so so we try and have a method in that every other surveyor will take a wall up to the top of the ceiling. So left hand wall, and then right hand wall, searching systematically all the little gaps, nooks and crannies for bats. And then on the way out, we look again, because it's quite easy to miss bats, particularly in some of the deeper crevices that are facing inwards towards the mine. So we'll reverse it and look again on the on the way out. So this bat we've got here Helen is just clinging to the wall close to the ceiling. How are we distinguishing what it is?

Helen Ball:

Okay, well, we know it's a Myotis bat from the shape of the tragus, the very pale belly. In these systems, we get a lot of whiskered and Brandt's very very difficult to tell apart even in the hand. But we look at some we tend to get a jizz if you see them quite often, the whiskered in the Peak District are often a little bit smaller, quite dark. The Tragus is a little bit of a different shape, we look at the shape of the nostril. So often it's gone on jizz in the in the caves but because we can't handle them because we can't test the fur for DNA. We always put them down as a possible whiskered and possible Brandt's. And quite often they're just literally written down as whiskered/Brandt's. Oh we're doing well. That's 10? 10 up to there already! Brilliant. One there.

Steve Roe:

This one is quite different. This one's a lot paler than what we've just seen. He's got a much wider tummy. So what's this?

Unknown:

So this is a Natterer's. This is the most distinctive Myotis we're getting the caves and when you're learning about Myotis bats the first one you would learn is Natterer's. So it's got a really white pale belly. They're also known as the red arm that because they've got quite Pinky arms, very long ears that sort of curl round, little bit at the tips. Pink ears, long tragus, Pinky nose, very, very sweet bats, if you can see the the feet and the tail membranes have quite long bristles on them to be very distinctive that and that's the first one you would recognise this as a natural. Once you've got that one, it's a case of then trying to get your eye in with a Dauby, and splitting off whiskered, Brandt's, Loads of cave spiders as well. And the other interesting thing is the tissue moths we get on the limestone. So these tissue moths that we're looking at here, we've seen quite a few of those and we've seen a few Herald moths as well. Are they a species which are regularly found underground.

Helen Ball:

Yes, yes. So Herald moths are quite a widespread moth and they share similar requirements in the winter for as bats so they tend to roost in cool stable, not too damp. underground systems or outhouses. Buildings that are not heated. The tissue moths are a type of geometric math, and they're quite a notable species on the limestone. So they're quite are restricted in distribution. And whenever we see them in the caves, we always send those records in because they're a notable find. [It's] Getting lower, you having to stoop more. I'm not as tall as you. For listeners at home I'm currently doubled over. I'm not as tall as you Steve, I can just about stand up. So there's one there. That looks like a Natterer's

Unknown:

I I mean that one's tucked really deep inside crevices? Do we know have any idea of why some are out in the open and some so deep in crevices?

Helen Ball:

No I don't think we do. Now, I guess. They're all looking for their individual requirements. Some might have less fat reserves and others so someone to go deeper into hibernation. The ones around the entrance may have only just moved into here. So a few years ago. It was filmed for springwatch. And I came down at the end of February just to check where the bats were. And during the intervening days, there was snow and ice, it was absolutely freezing and we came back to film. And the majority of the bats had moved positions within that time. So even in very, very cold conditions, they're still moving about within the caves system and potentially between caves and mines. So some will be hung quite out in the open and a little bit twitchy because they're not that deeply in torpor, whereas other ones like this one's really deeply tucked away a long way from the entrance very stable conditions. And looks like it's going to be fast asleep for a couple more weeks at least.

Steve Roe:

I know we've got a bat because I hear your camera's going!

Surveyor:

Well I photograph spiders and moths as well. So that was a moth that was down about this height a bit further along did I hear you say it was

Unknown:

Was it was the grey one? Tissue tissue moth. They're quite notable species. Yeah. Yeah.

Helen Ball:

So it's nice to see them. Are many moths overwinter as adults. Gorgeous. Really pinky ears hasn't it. Very pinky ears pink arms. That one's fast asleep as well.

Unknown:

So what's this thing that we've come to it looks like a dry stone wall inside the mine It does. Yes, it looks nice. But looks can be deceiving. So this is called a stack dead. So the miners when they used to blast away and chip away the rock, any of the rock that was not needed so it had no lead or it would be stacked up along the sides of the adults or even sometimes at the side of the shafts completely unstable. No mortar holding it together. Very very dangerous if you coming into mines and you don't know what to look for. Definitely something you wouldn't touch or climb up.

Steve Roe:

Despite the fact they look great for places for bats to hide

Helen Ball:

great places for bats to hide. Yeah. But the name gives it away, they're a

Unknown:

stack dead they're erm dangerous and a bit useless as well in terms of the rock [call of Daubenton's further ahead] Oh Dauby. There's usually Dauby deeper in. Usually on the left just before that turn low down.

Steve Roe:

So Helen what makes this one a Daubenton's bat?

Helen Ball:

Genetics!

Unknown:

So we've got a Dauby bat here. Really good view of it. And lots of people say the look a bit teddy bear like so very short. squatty is little pinky face, pale tummy, but not as pale as a Natterer's and very, very big feet. So they use those feet for gaffing insects off the surface of the water, which is an adaptation of this species in particular, and this one, too is very deeply in torpor. So we're well into the afternoon. Now we've just done the fourth adit. And Helen what we found so far? Numbers have been good. So far, we've got had a total of 41 bats, five species, we think assuming that we've had both whiskered and Brandt's, the majority of bats of things so far have been Natterer's. So what's the history of these minmns? What the What were the guys mining here? So these are lead mines, lead adits to be specific. The Peak District is notable for lead mining. So in the sort of 17/1800s It was the most important thing for the whole of the national economy besides farming and wool production. So for a couple of 100 years led was vital to the country's economy and particularly important for this region. So they will money for lead lead was really important for things like windows useful water carrying devices. Ammunition and initially, a lot of the lead was mined at the surface at rakes. But once all the surface deposits had been exploited, they started to dig shafts down. But on hillsides as steep as this, the quick way to get along to the lead ore was to mine horizontally into hillside, hence the name adits. And they used to mine and follow the lead or along the fissures until they'd exhausted that seam. Initially, it was done all through handtools. But into the 1800s, they start to use explosives. And in these adits in particular, you can see some of the the boring where the rock was bored, and then gunpowder was put in and the rock was blasted away.

Steve Roe:

So what's the link with Chatsworth house in these mines?

Unknown:

So as I say, mining, and in this area, copper as well was, were really important to the economy, it was strictly speaking, to all part of royalty, it was owned by royalty. But the titles were that were farmed out to major landholders, and important people in the area. So Duke of Devonshire being one. And in the Peak District, there was a thing called free mining. So anyone who came across a decent seam of Lead or was entitled to mine that they had the title of the mine and it even surpassed landowner rights, but a proportion of the profit from the lead had to be paid in duties to the head honcho with the area. And in this area, it was quite often the Duke of Devonshire. And it helped to pay for a lot of the things like Chatsworth and Hardwick Hall.

Steve Roe:

Nice, how many more, we got to do?

Unknown:

A couple more adits just further up the hillside. So we'll wind our way up the hillside and then we'll get to the top and team up with the other team and find out what they've got. [Helen discussing results with other team at the end of the day "12 Natterer's, 11 Daubys 5 WABs no BLE's" "Oh we've had a few BLE actually, one singles per adit"]. So how 72 in comparison to previous years Helen. So the total count for upper and lower adits is 72 bats, which is one of the highest counts we've had of all the years of monitoring, we need to check whether to see whether it's the highest or how close to the top it is. But that's a good count. All five species, as far as we can tell, in terms of telling apart whiskered/Brandt's, probably the most numerous being Natterer's I would have thought. But again, we need to check the records when we get back. So we should say all of this has been done under a Natural England licence. Why is that important for for this sort of work? Yeah, so this is all done under our sort of level two scientific licences, which allows us to disturb that's for the purposes of collecting scientific information, and data. Obviously, in order to make sure we don't disturb the bats because they're deep in torpor hibernation, we limit the number of surveys that go into the caves into the adults, and we make sure that we don't look at the bats for too long with the torches, and use torches that don't give up a lot of heat. And any bats that look like they're waking all this starting to twitch, well, we'll leave and continue on the survey.

Steve Roe:

So where did these results go,

Unknown:

So as well as the results going into the local bat group databases. The results also feed into the national bat monitoring programme, which is a national programme that looks at monitoring bat populations over a number of years to see whether the populations are faring well or badly.

Steve Roe:

So presumably having this longer term dataset is more valuable for for that study,

Helen Ball:

very much so and particularly winter hibernation check data as well, because the numbers tend to be more stable and more representative of what bats populations are doing in the area, rather than more active routes in the summer that may be roosting in Split numbers or in different places to where they often route.

Steve Roe:

And last autumn we did for the first time ever autumn swarming surveys, we did find evidence of autumn swarming, what impact will that have on the management of the reserve for Staffordshire Wildlife Trust?

Unknown:

Well, the first thing is we need to feed the results to the Wildlife Trust. They know them in a preliminary basis, but we're due to prepare a report that details all the hibernation monitoring since the early 70s. And then coupled with that the results of the swarming surveys. We'd always suspected for a number of years that the adits would have been used for autumn swarming for mating in the autumn, given the large number of bats using for hibernation, but also all the droppings that are in the adits, suggesting that bats are flying into and out of the adits. Summer surveys of the adults have revealed very little roosting. So obviously the droppings had gone into the adits by bats being active. We came down in August and September, and did some harp trapping and mist netting at the entrances of two or three of the larger adits. And we found large numbers of bats swarming around the entrances. So that has not only shown the site is very important as long term hibernation routes for a number of species. But it's also significantly increased the conservation importance of it, the swarming mainly because swarming sites are visited by very, very large numbers of bats, and they will be pulled in from quite a significant radius of the surrounding area, potentially 10s of kilometres. So given the Peak district has several 100, if not 1000, caves and mines mapped by various caving communities in both Staffordshire and Derbyshire bat groups have had evidence of bats in almost all of the ones that we've surveyed so far, which is a very small percentage of those. Presumably that means that the Peak district is really important for both hibernating and autumn swarming bat populations, if there's a small number cost that many sites? yes, very much. So I think it's made it of regional importance, if not more, because, as you say, the number of caves and adits it's in really good habitat because a lot of the habitat were in SSSIs, next to river systems, woodlands and grasslands, to really diverse, so good insect populations. The habitat overall is really good for bats. And obviously, that's coupled with really good hibernation and swarming sites. So there'll be 1000s, if not 10s of 1000s of bats that are visiting these over the course of the seasons. And that makes these have regional importance. And there's no annex species makes a change, it's usually only horseshoes and Bechstein's and barbastelle that make anything important these days, but yet lots of Brandt's and whiskered. thanks to Helen and the rest of the team for sharing the day with us. And when we got home, we checked out that survey compared with previous years, and the 72 bats found by both team was actually a joint record with the survey undertaken in 2005. If that's inspired you to get involved in bat conservation and would like to improve your skills to help your local bat group, then you'll be glad to hear that the big bat skills event online is returning on the 12th of February. The event brings that workers together online for a range of workshops to develop their skills and knowledge without having to gather in person, you can book your place on the Bat Conservation Trust website, check out the show notes to find the link. Thank you to you guys, for your continued support for BatChat. And for streaming this podcast. We're really pleased that you enjoy it so much in these uncertain times. We all need things to keep us connected. So if you know someone who's never listened to a podcast before, we'd love it, if you could show them how to listen and introduce them to BatChat. We will have another episode for you in two weeks time when we're going to be joining some of the team at Chester Zoo to discover how they're helping conserve bats over 6000 miles away. So join us then.