BatChat

Barbastelles at Paston Great Barn

November 17, 2021 Bat Conservation Trust Season 3 Episode 25
BatChat
Barbastelles at Paston Great Barn
Show Notes Transcript

S3E25 This week Steve is on the Norfolk coastline in the East of England visiting Jane Harris from the Norfolk barbastelle study group. Paston Great Barn dates back to 1581. It’s a huge thatched barn made of flint, brick and stone measuring 50 meters in length and about 10 meters wide. Despite it’s size, driving south along the coast road it’s very easy to miss as you pass its end flint wall and not until you glance in your rear view mirror do you get a feel for the expanse of the structure. Hidden away inside this SSSI and SAC is an important roost of rare barbastelle bats which emerge from the barn at night and either head off down the country lanes or to the cliffs along the beach to forage. Jane and Steve discuss the work done by the research group to discover more about barbastelles in Norfolk as well as this important roost where it all started back in 1996.

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Barbastelle bats at Paston Great Barn with Steve Roe & Jane Harris. BatChat Interview May 2021.

[00:00:00] Steve: Well as promised your next episode in series three of BatChat is here and today we're heading to the East of England. I'm Steve Roe, a BCT trustee. If you're a returning listener , it's great to have you back once again. And if this is your first time, welcome along Episodes are released every second Wednesday from now until the spring.

And you can join the conversation online. Use the hashtag #BatChat. That's all one word. As we meet each of the guests in this series, you'll hear stories from people working to make a difference in the world of bat conservation. You'll hear from people who care about individual species, people who concentrate on one particular part of bat ecology and people who are working with bats at a landscape scale, as well as keeping up with the latest news and hearing from people in the world of bats.

We hope that you'll be inspired to get involved because bats need our help. Today, we meet one of those people who is interested in one [00:01:00] particular species. The barbastelle, Jane Harris is part of the barbastelle study group in Norfolk on the east coast of England. Back in May, whilst I was on holiday in the area, I drove down to Paston Great Barn, which is right on the coastline.

Dating back to 1581. It's a huge thatched barn made of Flint brick and stone measuring 50 meters in length, and about 10 meters wide, despite its size driving south along the coast road. It's very easy to miss as you pass it's end Flint wall. And not until you glance in your rearview mirror do you gets a feel for the expanse the structure.

I first got to visit Paston as a teenager when I was getting interested in bats. And whilst on a family holiday met with a surveyor who was undertaking regular counts of the colony and I can still remember being taken inside this huge structure and being shown the colony of barbastelles tucked away above one of the doors and staying to count them as they flew out over the sides and down the dark country lanes, listening to their distinctive castanet echolocation calls 20 years later, and then back and you join me inside the barn with Jane Harris, who was [00:02:00] describing the space we're stood in.

[00:02:03] Jane: Well, we're in the medieval thatched barn, which is, I think one of the biggest in the country, it was used by the, the famous Paston and family in the past. And it's a huge barn with joining cart sheds. That was, I think, really came to prominence when sheep and wool farming important in Norfolk. Andit's a brick and flint and thatch with something like 20 trusses that go up different levels to the roof.

So it's, it's full of timbers, which have mortice joints and gaps in them right up to the roof. So it's, it's in many ways a bat heaven because for crevice living bats, there are lots of opportunities here. 

[00:02:50] Steve: So Jane, we're here to talk about the unusualness of the site because it's used by barbastelles.

Why is it so unusual for that species?

[00:02:58] Jane: Well, barbastelles are primarily regarded as a Woodland species and at the time the roost was discovered here. It was the first one known in a building. I think there may be more now, but it's certainly the most significant one at the time. And the reason it seems to be used by barbastelles is the.

It functions like a surrogate Woodland with all these timbers, with crevices. So within it, they can undertake their normal behaviour of roost switching without going elsewhere. And that's what they do. Although we do find they're a little bit more faithful to some of the lintels and staying in them for a long time, which probably isn't quite the same as you would get in, in the woodland where they switch more often.

But I think now they'd been faithful to this barn since about 1996. They come back every year. The barn is obviously undisturbed because Natural England now have it on lease and it's an NNR [00:04:00] and it's managed very carefully and the colony is monitored annually. So they're in safe hands here and there are anecdotal reports of them being around way before the barn was taken over by Natural England. And 

[00:04:15] Steve: it's quite unusual to have a building designated as a National Nature Reserve in its own right? That's right. 

[00:04:21] Jane: Yes, I think so. It was it was under threat because it was it's owned, I think by Norfolk buildings, preservation trust, and they were hoping to convert it to a visitor center as they had done Wroxham barn that isn't very far away from here.

Norfolk bat group. John Goldsmith you may remember him did some surveys discovered the colony. And from there on it was quite a long procedure to work out what would happen. And in the end it was designated as a NNR and SAC and SSSI, obviously, and the lease was going to natural England for 50 years, I think.

[00:04:57] Steve: And it, like you say, it's unusual, to have barbastelles in a [00:05:00] building cause they are normally considered a Woodland species aren't they?. I mean, what's the Woodland situation in Norfolk because looking at the map, it's quite arable areas 

[00:05:07] Jane: That's right. Well, it was always considered that this roost was unusual.

Not because just because it's a building because it's a building in an arable area. And after the roost was discovered here interests in barbastelles grew in Norfolk. The Norfolk barbastelle study group was formed. That was 2007. And that really was partly spawned by. Ash Murray who was site manager here for Natural England and Keith Zealand who was manager of some of the big Woodlands at national trust Woodlands at Felbrigg and Sheringham Park.

And Keith knew from the LBCT monitoring Woodland monitoring protocol, that they were barbastelles at Sheringham. So he and Ash formed the group, and we started looking at those Woodlands, initially the ones mainly north Norfolk. But also some privately owned in west Norfolk and we've gone on to [00:06:00] look in south Norfolk where there, the interesting thing there is the Woodlands are much smaller and more isolated, but where they have suitable roost trees, we're almost certain to find barbastelles.

So we're now getting a picture throughout Norfolk of what barbastelles need and where they will actually use the Woodlands for maternity [roosts]. 

[00:06:22] Steve: How have you found all that out? Have you actually tracked these bats?

[00:06:25] Jane: Right. When, when the group started, we were mainly looking at distribution, using transects and building up methodology for that.

But we very soon realized that if we wanted to find out more about where the breeding colonies were, we had to radio track. So initially we had Chris Vine from Cambs group helping us until they got trained up to trap and radio track. And we've been doing that ourself since 2012, I think. So we've been targeting all this Woodlands.

We started the national Trust's ones Sheringham Park. Blickling, Felbrigg. And then at the [00:07:00] Ken Hill Estate over in the west, which is an interesting one because they're now rewilding. So we hope to go back there and see how the barbastelles are doing. And then various of the Woodlands close to Paston because we wondered whether it was an isolated colony, whether any other, barbastelle maternity roosts within sort of an interactive area. And we found one about six kilometers away to the south and the foraging ranges overlap. So that started to tell us something about potential interactions between colonies, perhaps passing. Isn't quite so isolated. And another one, about 10 kilometers to the west. We've also started looking in different habitats different Woodland types down the south Norfolk. The Woodlands are slightly different, more Hornbeam and Ash, but there is Oak amongst them. Some of them are heavily coppiced, but most of them have some non-intervention areas. And we were finding barbastelles in those.

So we find them [00:08:00] in south Norfolk as well. The gaps at the moment are the Broads. We don't know very much there. You've got the wet Woodland, but there is some Oak in some of them Calthorpe broad, which is another NNR we've looked at another maternity colony there that's down south-east of here. More towards the coast, not so far away.

We don't know much about west Norfolk 

[00:08:19] Steve: I mean, it sounds like you found quite a lot of colonies across Norfolk. Do you know roughly how many? 

[00:08:25] Jane: The group's found 15 maternity colonies by radio tracking and another three where we've caught post-lactating females and the roost potential of the Woodlands is high.

So we're pretty sure they're there as well. If you add the ones that have been found. For example, the north distributor road ecological surveys, the Northwest link and one or two other sources we're up to Norfolk at least 24 barbastelle maternity colonies scattered from north to south. But as I say with a bit of a gap to the west, apart from Ken Hill on the edge of the Wash [00:09:00] and the Broads don't know much about the Broads. 

[00:09:03] Steve: Thinking back to sort of 30 years ago, when we didn't know much about barbastelles at all, you know, actually it seems like the population density here in Norfolk seems pretty healthy compared to what we used to know about them at least.

[00:09:16] Jane: It does and there are historic records of barbastelles in hibernation sites in the past. We rarely see them in hibernation sites now. I think probably because the winters aren't cold enough, but it was always thought. For example, Frank Greenaway's work and so on, that barbastelles would be in heavily wooded river Rhine landscapes.

So what were they doing in Norfolk? So that's really what the group was setting out to look at. And we find that if they've got a suitable roost Woodland, Which there are quite a few. They are able to feed in the associated what I call arable, mosaic, particularly rather a lot of good hedgerows, hedgerows I think are really important.

And [00:10:00] sometimes you get a little tributaries or ditches with a lot of Woody vegetation along them. They'll use those a bit of rough pasture mainly but also if their colonies are within about five kilometers of the coast, particularly where they're cliffs, cliffs are important. They will visit them.

For example, from here past, and very often the first place they'll go to forage is the cliffs that monthly. And if the weather is right and there are insects, and I think it's the shelter, that's the important thing. They will stay there all night, but if they get that and maybe it's an unsure wind and there are no insects, they'll come straight back, go back down south to Bacton woods. So the coast is important where the colonies are near the coast. The Fellbrigg colony forages at Cromer on the cliffs. They're further west, it's more sand dune and salt marsh. We get some visiting and barbastelles on the coast, but not, not so much as where we have cliffs. I think it's the shelter tht’s really important.

[00:11:01] Steve: I was going to say, because if the, in a natural or more normal Woodland environment, you expect them to be on the shelf side of the Woodland. So you think it has to do with the weather? 

[00:11:09] Jane: I do? Yeah. Weather influences where they're foraging. 

[00:11:12] Steve: Yeah. And for listeners who have never seen a bat being tagged before, can you just describe what a radio tag looks like and how it sits on the bats?

[00:11:21] Jane: It's basically the top of the tag. It has the battery in it. Electronics, the workings, and then the antenna is a very, very fine antenna that's usually 15 to 20 centimeters long, depending on what you want. There are different weights of tag. But the ones we use are usually about point three, six or 0.45, because the guidelines are that the weight of the tag and the adhesive, which is a medical glue, mustn't be more than 5% the weight of the bat.

So the barbastelles we really want them to be over eight grams to take tags like that with comfortably. So once [00:12:00] we've caught them and we clipped a little bit of far off from between the shoulder blades. Put a little glue on, on where we've clipped on some on the bottom of the tag. When that goes tacky, you put the tag on and just gently.

firm the hair round it and leave it, put the, that bat in the bag and leave it until the glue has gone firm. And then we'll make sure that's warm and release it again. And then it's long nights after that. 

[00:12:31] Steve: We'd say glue and it's, it's a special glue, isn't it? That it's not like a normal, it's not like using sort of super glue or anything like that is it? 

[00:12:37] Jane: No it's the medical, the various ones medical adhesives often use for colostomy bags, you know, that type of thing.

So the tags fall off eventually. Sometimes they come off quite soon and I think that can often be if a bat's been making its way into a crevice, or sometimes they stay on longer than that, then how 

[00:12:55] Steve: long, how long does the battery last usually on these things? 

[00:12:58] Jane: That depends on [00:13:00] how the tag is set up.

The number of beats per second, the length of the pulse. We go for about two weeks. You can get longer, but then the pulse rate will be slow. So it depends what you want. If you want to track a moving bat you don't want the pulse gap too wide, particularly barbastelles, they move so fast. 

[00:13:19] Steve: You say they move fast...what sort of foraging area, how, how many kilometers from the roost will they forage? 

[00:13:25] Jane: Well, the core sustenance zone is six kilometers radius from the roost and we found that that's about right, but bearing in mind where on each tracking a, that pregnant and early pregnancy females or post lactating ones.

So they, they have an affinity to the maternity roost. They're probably not going as far as the males would go for instance. So we find, they go on average about five kilometers, certainly from Paston. We haven't had any go any further than that, but, you know, we only check a certain small percentage, but I know in the past males have [00:14:00] been recorded by the people going 15, 20 kilometers.

[00:14:04] Steve: And is it just barbastelles you've got hair in the, and all of our, that or the bats? 

[00:14:07] Jane: No, that there is a significant Natterer's roost as well. Mainly in all the Mortice joints, there's many Mortice joints and they, they arrive earlier than the barbastelles. So they should come anytime now because they give birth a bit earlier.

And all the lining papers down under each of the trusses helped me to know where they are. And then I can use the cameras to try and get a count of how many about.

[00:14:35] Steve: Jane's just said lining papers. So. what looks like more white wallpaper rolled out underneath each of these, these trusses and weighted down.

And the one that we're stood next to has got a scattering of Natterer’s [droppings]

[00:14:47] Jane: It looks like the first visit of the year. Yes. And that's in truss T5. So all the trusses are numbered. So we know which ones. They should, the numbers should start to build up soon, no sign of the barbastelles yet, [00:15:00] but I would expect they were about end of May, beginning of June. 

[00:15:04] Steve: And scattered around as well there's a number of what looked like security cameras. 

[00:15:08] Jane: They are, the roost here is monitored by different cameras in the past, but things have improved. What we're using now are basically infrared security cameras, which don't give that good quality video, but that really flexible in that you can set them up to record cause they're linked to a recorder whenever you like.

You don't have to come in. And keep disturbing the roost and they are linked to a recorder with a monitor in the barn next door. So the cables feed through and you can see what's happening from that. So I can, I get a count every night and, and I can see what's happening to the colony right through the maternity period.

[00:15:49] Steve: Nice. and they're on little tripods as well so you can move them around and follow them. 

[00:15:53] Jane: Two fixed ones under the two big door lintels where the barbastelles are and spend most of their time and four roving ones [00:16:00] that I can use on the Natterer's if I can work out where they are! 

[00:16:04] Steve: And in terms of the Woodland roost you've found elsewhere in Norfolk.

What I mean, the trees that you find them roosting in what sorts of features are those roosts in are they in woodpecker holes or bits of…? 

[00:16:13] Jane: No, loose bark, loose bark. They will use splits and cracks, but loose bark seems to be the most predominant type. And we get that a lot on Oaks and sweet Chestnut, probably in that order.

Those, those two are really important, but you get you can't get loose bark on other species and they will use them. I think the maternity colonies seem to go more for the Oak and sweet Chestnut when the colony's dispersed and you get a bit more variety, but those, that type of roost, the Oak and sweet Chestnut with lots of loose bark is what we have in the colonies north of Norwich, where the Northwest link is supposed to go the road that joins the NDR with the A47.

And [00:17:00] there are so many wonderful roost trees there. And the work that's going on has shown that there is a barbastelle colony which is going to be definitely impacted by the road. So the work is going on studying that at the moment. 

[00:17:13] Steve: And you say a large roost, you know, what's, what's the average size for a barbastelle maternity colony in these woods?

[00:17:17] Jane: Right. I think it varies a lot. What we found in the sort of trees we've been looking at sort of Woodlands is probably up to about. 25. Sometimes you get them in a bark collar, round, an aerial bough and then we might get 20, 25. If it's more of a bark slab, which might make it bigger, you might get up to 35, something like that.

I think the big colony in the in these Woodlands north of Norwich It's something like a hundred over a hundred, but it's a very large tree with many potential roosting places. So it's hard to answer that. I think it depends. What space the feature allows probably [00:18:00] [depends].

[00:18:00] Steve: Nice and diplomatic! And you touched on earlier, we talked about, you know, a bit of interaction between the risks.

What, what have you found out about the interaction between the different colonies? Is there, is there definite interaction or are we still not sure? 

[00:18:12] Jane: That's interesting. I mean, we found this some overlap between Foraging areas of different colonies. We found that for passing with one about six kilometers to the south, we've found that with on a Blickling with another one nearby. In terms of whether the bats move between them.

We don't know, but another strand of our work was came out of this question of whether Paston was isolated because it's in an arable environment and by chance, really Built up collaboration with Dr. Anne Edwards [of the] John Innes Institute in Norwich. And we thought it was feasible to start trying to look, see if we could get enough good quality DNA from faecal samples to look at the cytochrome B on the gene on the mitochondria and see what the haplotypes were because there was already work on those [00:19:00] published.

So that's what we've been doing. Collecting faecal samples from colonies all over Norfolk, including Paston that work is just about coming to fruition. I think it may have some interesting results which may give an indication of the status of barbastelle colonies in Norfolk, whether they are in good condition in terms of genetic variability or maybe not.

But that's all I can say. We are now teamed up with somebody at UEA because the analysis is quite complicated. I think. So watch this space for that, but that was a standard of work that came out. Partly because of the Lawton review and thinking about it colonies and landscapes being interconnected and were they vulnerable or was that good gene flow, which would help them be more resilient in the future?

So that, that was one strand of what we do. And hopefully we'll get something useful out of that. And 

[00:19:59] Steve: [00:20:00] what do you see the next steps for the project being into the future? 

[00:20:03] Jane: I think we need to look at the areas we haven't looked at before, are the Broads important and also the west of Norfolk. One of the things that Ash Murray particularly at tried to do is where you have so many, multiple roosts within a Woodland to try and do synchronous counts, to get an idea of colony size and use that for monitoring in the future. So that's something we want to try to improve on. And although also in the, the Woodlands north of Norwich we are looking at ringing there as well, more long-term monitoring. So monitoring is important aspect. The genetic work we might follow up, if that looks to be interesting and then filling in filling in the gaps, I'd also of course, trying to influence the new land management scheme.

To try to improve habitat, particularly hedgerows, and linking up for barbastelles. So there's lots of things we would like to do. 

[00:20:59] Steve: So I mean, a [00:21:00] lot of work has gone on gone on in the last few years and the picture of barbastelles has changed quite a lot from what we used to know. What sort of sense do you get for the conservation of barbastelle bats here in Norfolk and the rest of England?

[00:21:13] Jane: I find that hard to answer because I don't know if there's any work that looks on a, on the sort of geographical scale that we've looked at. I mean, we're looking not at one colony in perhaps one Woodland or two Woodlands, but we're trying to get an idea of the, of the status right through the county.

So I don't know how to answer that. All I will say is I think. I think they're extremely vulnerable still because of land management because of infrastructure schemes, particularly the Northwest and link. I think that would be a disaster. If that colony is, is Lost or it declines as we know already from the Northern distributor, the first bit that the colonies have gone from there.

So I think that is really something that's very important to [00:22:00] try to influence. 

[00:22:02] Steve: And in terms of the future of this place, you know, this, I mean, it looks very solid and over here, I mean, what ongoing restoration or maintenance is there? 

[00:22:11] Jane: Right that's natural England's responsibility. It was thatched some years ago.

And various bits of maintenance work had done. Obviously when the barbastelles aren't here, it's also a hibernation site as well. So I did mention there were Natterer's, but we also have pipistrelles, soprano and common pipistrelles and brown long-eared's, not breeding, but they're hidden away often. So it's, it's quite an important hibernation site.

So the work is always done very sensitively. Any work outside you see, there's quite a lot of vegetation keep clear that's done with an electric strimmer now to keep the noise down and all that sort of thing. And the structure of the barn is, they have to keep the walls clear so they can monitor whether any cracks or subsidence or anything like that.

So that's ongoing all the time at the moment. I think the thatch is in good, good condition. So I don't [00:23:00] think anything is planned. 

[00:23:01] Steve: And if people want to find out more about the group and the work you're doing, have you got a website? 

[00:23:06] Jane: We have got a website? Yes, Norfolk barbastelle study group. And of course we will wrote up all our work, which we were very pleased to be able to do and get it in British Island Bats because it pulled together everything from 2007, up to 2019.

So Maybe the next 10 years will produce something more. . 

[00:23:26] Steve: Jane Harris. Thank you very much. 

Jane: Thank you.