Bat conservation in action with Jim Mullholland

S3E31 This week Steve is on the Tortworth Estate in south Gloucestershire with Jim Mullholland. They're joined by a voluntary team of arborists who are assisting Jim with his 5 year project to create natural tree features for Bechstein's and barbastelle bats. By using chainsaws to create different crevices and cavities within living trees, the team hope that they will be taken up by colonies of the two bat species which are present in the woodland Steve is visiting today in this episode. The episode starts on a sunny spring day in an ancient woodland with chiffchaff singing in the canopy overhead. As the episode moves down to where the team are working for the day there's more background noise than you're used to on BatChat because the woodland is right next to the M5 motorway.  

• Jim Mullholland is on twitter and Instagram
• Jim has a YouTube channel with a number of videos of bats inside tree roosts.
• The Tortworth Estate opens to the public on certain days of the year. Find out more here.
• Listen to our other episodes on veteranisation with Jim and Vicky Bengtsson
• A guide to veteranisation techniques is at this link.

Join the conversation on social media using #BatChat:

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For more bat news, head to our website https://www.bats.org.uk/

Producer: Steve Roe @SteveRoeBatMan
Cover Art: Rachel Hudson http://rachelhudsonillustration.com/

Transcript

Steve Roe: 0:09

This week we have Bat Conservation in action for you in South Gloucestershire. This is BatChat from the Bat Conservation Trust. Hello, and welcome to BatChat. This is the podcast where we bring you the stories from the world of bat conservation. I'm Steve Roe a BCT Trustee. And if you're a regular listener, it's good to have you back with us. And if this is your first time listening to BatChat, welcome along. Episodes are being released every second Wednesday from now through to the spring. And you can join the conversation online using the hashtag BatChat that's all one word. As we meet each of our guests, you'll hear from people working to make a difference in the world of bat conservation. 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. Now if like me, you're looking forward to the sunny days of spring, you'll like these next few minutes. Back on episode 11 we had Jim Mulholland talking to me about his veteranisation of trees projects. And last March I joined him out in the field on an estate in Gloucestershire, in some woodland, where a team of arborists are volunteering their time to help him with his projects. So we joined Jim at the start of the day in an ancient woodland, where he explains what the plan for the day is, and tells us about the project he's got running on the estate. Later on in this episode, there's slightly more background noise than you'd used to hear on BatChat because of the site's location right next to the M5 motorway. So it's a nice spring day, at the end of March, chiffchaff singing, and Jim Mulholland is back on and we're in South Gloucestershire on an estate called the Tortworth Estate. So Jim, nice to have you on again, what is the Estate and who owns it?

Jim Mullholland: 2:01

The Torworth Estate is perhaps one of the best states in the country for bats, as Steve raises his eyebrows at me

Steve Roe: 2:08

Big claim, big claim

Jim Mullholland: 2:09

It is a big claim. But I can substantiate that. We have 15 of the UK species here. The only ones we're missing a grey long-eared and Alcathoe, and I'm hopeful for Alcathoe like everyone else is I guess in the country.

Steve Roe: 2:21

I mean, that's pretty good, isn't it?

Jim Mullholland: 2:22

It's pretty good. It's not bad at all. And considering it's five minutes from where I live, all the better. It's a privately owned estate. I think it comprises somewhere in the region of 2500 acres. And it's a mix of wonderful habitat. So we are currently sat in Daniels wood. And this is an area of ancient semi natural woodland. And it has other habitats such as organic pasture has two freshwater lakes. It has lots of old buildings. And my original involvement here was to do with lesser horseshoe bats, which were hanging up in the outbuilding of Robert and Sally's house. And they kept seeing all this poo on the mower and thought it was a huge colony of mice that had moved in and then suddenly decided to look up and saw these bats. And it kind of started from there as I was involved with some work with lesser horseshoes, and it snowballed from there. And so we've been involved with Nathusius', the National Nathusius' project led by Daniel Hargreaves down at the lake. And we recorded them down there although we didn't catch any. We've had sightings of Leisler's I had a wonderful evening where I was looking at about thinking, it looks like a noctule, it sounds a bit like a noctule but it's a little bit too high. And then all of a sudden, the noctule appeared next to it. And so had the confirmation and then subsequently we find a young Leisler's in about a box as well. I've been working here since the it's 2013. And my work for the last five years or so has been very much focused on baps and trees here. And so my evidence base for the two talks at the National Bat Conference come from largely from data from these sites. And we're on to the new chapter today.

Steve Roe: 4:01

And the rumble that we can just hit the background is the M5 motorway so for listeners who travel south on the five and pass the Michael Wood services, the block of trees over the hill on the left is basically where we are. So what are we doing here in Daniels wood. There's about seven arborists working just down at the bottom of the field from us. And we'll come on to that later. But what are we doing up here in Daniels wood.

Unknown: 4:25

At the moment I'm trying to get my tablet to work, which isn't playing ball. But we are doing some work as part of our five year project funded by people's trust for endangered species. The arboricultural association is supported by Stihl and the title of that is improving the future for to Woodland bat species. We have two main strands of the project. The first one is focusing on the efficacy and efficiency of tree surveys for bats. And it's a topic that I've spoken a lot about and raise the issue that the service that we undertake are really quite limited, I started some work trialling the use of trail cameras to see if we could use them use technology and replace surveyor efforts. So the first strand of the project is really just refining that. So we have a number of Bechstein's and barbastelle tree roots here. And we will be deploying those trail cameras to see if we can improve and refine that approach and and hopefully see that begin to roll out and improve our service for bats in trees. The second strand is then moving the next step, which is the really exciting step, which is can we create that roost in trees by wounding them in deliberate ways. And this is something that various people have tried for a number of years, I believe. And I think the the main limitation with previous work is that it's just not been monitored. And that's because it's very, very difficult to establish whether bats are using a tree. So we have the two elements of the project really coming together that we will create these features. And the design of those is very much guided by the data from the battery habitat key. And then once we have created them, we'll be in a position where we can use the trail cameras to establish whether they're used, and hopefully, they're used by the species that we intended to be used by. So one of the strands of the project is to look at the temperature and humidity regimes, both in natural features, the features that we create, and we are in Daniels wood at the moment, because we are going to put some data loggers in bat boxes to see how they compare.

Steve Roe: 6:25

I think last time you came on, I accused you of trashing trees. And then since then, we've had Vikki Bengtsson on the podcast and she talks about the project she's been doing both here in the UK and across Europe. And the results from that a pretty spectacular really so it's nice to see somebody else's taken on here in the UK, the data loggers you've got so they're their data loggers, the are familiar to people who do that work. And typically they go in caves and roost sites. How are you fixing them into that boxes today?

Unknown: 6:54

Good question. Not really sure. The flat Schweglers have a section of wood at the back. So we will screw a small screw in that and then hang them from a piece of wire. I think for the rain Schweglers I'll have to settle for just resting them at the bottom of the box and hope that that's gives us some data. I admit that that's not where the bats will necessarily be roosting but it will give us some comparison, at least for an empty bat box and an empty cavity. Yeah, great stuff. Vikki was my boss at the ancient tree forum. Yeah, so that's my first box and the ancient tree forum and she's inspirational. Think we so this project actually came from working with Vikki on a European project called vet search where we were developing a certification scheme for veteran tree management. And I've kind of had this realisation that we do fantastic work in ecology, we do fantastic work with bats, and typically we scrimp and save and try to find the money to do the work. And I was delivering a training course with Vikki. And she basically flipped that on his head and said that through the years she worked in conservation, they will find money here, they will scrimp and save and try and get what they, they need to do an okay job. And actually, we do fantastic work, just need to sell it better. So we need to say, this is valuable for this reason. And it's worth this much. And therefore I want this money, we should be going after the big fingers really. And it's about asking for what we need rather than what we think we will get away with. And so that inspired me, Vicki and I then were delivering another training course in Finland, we were sat in a bar discussing various projects and her work. And that's where the embryo of this project was born. And so I came back from Finland and within three weeks, the people's trust for endangered species had their current round of grant closing was finishing, that did not make any sense. Within three weeks, the people's trust for endangered species had a deadline for one of the grant applications. So I submitted and here we are. Now I need to focus on this because otherwise I won't run out of battery why is this tablet not working

Steve Roe: 9:11

So Jim, we finished putting out the data loggers in Daniel's would come down to the bottom of the fields. And we can tell we're a lot closer to the motorway. And we can hear bits and pieces of chainsaw noise in the background. What are the guys and the trees down here doing?

Unknown: 9:24

So they are working on the trees that will be used for creating the bat roosts. So the first step is to remove the top of the tree. And that's because we are cutting features into tree and we're worried about potential failure through torsional loading. So twisting motion of the tree. So that's step one. So we have four or five people down there at the moment, just taking the top set of trees. Then the next step we will be looking at actually cutting the features into the trees themselves. So we have two species we're catering for. We're looking creating roots for Becstein's and barbastelle and for each species, we are trying what we're calling instant roosts and future roosts. So the instant roosts, as the name would suggest, suitable once they are cut effectively, it's a bat box in a living tree. And this is similar to a lot of other work that's been going on previously, if cutting slits, etc, they are perhaps slightly more tailored to the individual species roosting requirements, that the idea is that yeah, we'll take a section of tree out kind of a wedge from the front, we take the back off of it, we cut an entrance into it, and then we reinsert that lid, effectively, the future roosts where we are cutting wounds into the tree with the idea of anticipating how the tree will respond and how it will grow after the wounding. So work from Vikki Bengston, who you mentioned earlier, she has a nest box designed to the incident routes is very much like the nest box designed but it's it's tailored for bats. Her work has shown that after maybe five or so years, the lead gets basically spat back out of the tree, as if the tree is rejecting it. Because it's no longer living, it's no longer part of that tree. So in conservation, we're looking at having various tools, and one of them might be an instant provision. But also we're looking at longer term provisions as well. So the future roosts are doing just that. So we cut features into the tree, they're open to begin with. As the trees continue to grow, they will callus over. And they will close over entirely. So effectively, what we should end up with something is very similar to a natural features that's covered in living functional wood. So we have water moving through that word, it means that the temperature humidity regime should be as close as possible to living trees as natural features as possible.

Steve Roe: 11:39

And why are these better than bat boxes?

Jim Mullholland: 11:42

We don't know at the moment is the question. So we are experimenting, I guess we are looking at can we increase the size of our toolbox. And this is something that Vicki talks about as well that they will not be suitable in all situations. We have selected trees here with the foresters that are of low economic value and low ecological value. So they would have heard of or otherwise been removed. And it's all about expanding the size of the toolbox. We know that that boxes have their place. But we also know from studies that the temperature and humidity regimes are not as good or not the same, at least as natural cavities. And the concern there is that the individuals that use them, especially if they're breeding, perhaps will be less healthy if they're less healthy, or they're giving birth to young that are less healthy, and well that have a knock on effect to the populations year on year on year. So it's increasing the size of the toolbox.

Steve Roe: 12:34

Right, we're going to head down the hill and on top some of the top guys were making a lot of noise

Jim Mullholland: 12:39

they are it's getting smoky here as well

Steve Roe: 12:43

sort of comes down the bottom field and we're now in fairly steep woodland, and we can see the traffic on the M5 motorway. There's a guys making a lot of noise up a tree. Taking the top of the tree out like it was

Unknown: 12:59

probably 15/20 metres up the tree. It's raining sawdust.

Steve Roe: 13:04

Once you taken the top out of this tree where abouts on the tree is he making this cut? making

Unknown: 13:07

the call, we will be creating them between five and 10 metres on the main stem. So we're focusing all of the features on main stem we chose five to 10 metres because that's what the data from the bat tree habitat key says that we should do. Basically it talks about the highest proportion of maaternity roosts recorded the trees are in that region. That could be down to bias in data. But obviously we know that there's probably a preference to roost at a certain height so below five metres is probably unsuitable and higher than that potentially gets less suitable as well because the bats experience more movements in the wind, etc.

Steve Roe: 13:43

It's not a very dense woodlands. It's quite windy about the winds. Quite quickly. Do you know that there are barbs and Bechstein's in this bit of woodlands or is this an area you've not surveyed yet.

Unknown: 13:52

So we're in Daniels wood still we're at the other end of Daniels word and the top end of Daniels words is in a U shape so overall the woodlands tend to be in a Y shape. If you mentioned sticking the the south end on bottom. We are basically the furthest north you can go and the furthest west you can go right next to the M5. The Bechstein's pretty much all roosted within Daniel's wood, albeit slightly further south than where we are. There is one tree roost that's, maybe 300 400 metres from here Bechstein's bats. The barbastelles however, they do use the woodland and I catch them on the rides in The Woodlands on the other side where we just were looking at the bat boxes. But to my knowledge, they don't roost in this woodland so they roost further south from here they roost further north from here, but I haven't yet recorded any barbastelle roosting in this woodland. The trees we selected we have three sites on the estates for creating these features. We have Daniel's wood where we are now. Next week, we will be working in a region called Hawkers Grove, which is further south and then we will be finishing off by one of the legs. And so we kind of span north to south maybe about two kilometres between the three areas. And that encompasses more of the areas where the barbastelle roosts are.

Steve Roe: 15:07

And what are the what are the tree species? When you're targeting? Are you targeting particular species for the two different species of bats? Are you just trying to connect with them,

Unknown: 15:15

I'm less worried about individual tree species, especially for the instant roosts. Because we're not waiting on any decay processes. We're not waiting on the trees to respond. We're essentially creating bat boxes and living trees, it would have been nice to use just one tree species for consistency. However, I had to go with what the forester provided me with essentially. So we have a mixture. And it's a mixture of oak mixture of ash, sweet chestnut, and some sycamore as well, it depends. The makeup of individual tree species varies through the three different woodlands that we're working within Ash is going to be an interesting tree species. The forest, as you can imagine, was very happy to give me all the ash trees that I wanted. But I limited in the number that we're using just through concerns over the longevity and future stability. I'm still happy to create them in them, I think it will be a useful experiment. There's lots of talk about at the moment about what we are going to do with ash trees. First of all, the hope is that we won't lose all the of the ash trees. Second of all, there will be some that will contract ash dieback but survive so they kind of get it and come out the other end. Okay. We know that trees that are in the more natural setting, more diverse ecosystems are more likely to be resilience to as diverse and so we're in at least in Daniels wood, we're in an area of ancient semi natural woodland, some fantastic ground flora around us at the moment. So the soil ecosystem here should be fairly healthy. This section we're in now is a non intervention area, with the exception of what we're doing clearly. So yeah, I'm cautiously optimistic about our ash dieback here, however, it is inevitably going to have an impact.

Steve Roe: 17:03

Yeah, I mean, you say the grand falls nice. I mean, you can't actually see much soil at all you've got bluebells starting to poke through the carpet of dogs mercury, there's some wild garlic starting. So the smell of thats drifting down the hill. Yes, nice wood anemonie as well.

Unknown: 17:20

Okay looks liek the final guy has come down. It's teatime!

Steve Roe: 17:25

So after a tea break from taking the weight out of the top of the canopy, we join Mark back at the tree where he's now going to create the actual feature for Bechstein's on the trunk. So the feature that's Mark here is that to make say, an instant feature, so it's like creating a what essentially a bat box would do within a natural tree feature. So they're cutting a long rectangular block of wood out of the main stem of the tree, the tree trunk, and then they're cutting in from behind to release the back of it. And that's been released and lowered down to the ground and a chunk of that shaved off so that when it's placed back in the mainstem and put in place with nails or screws, there's a natural cavity then then created and that's what Mark is about to create. So Mark was just telling me that he's been an arborist for about the last 20 years. Is this the first time you've done this sort of work on this? For this reason?

Mark: 18:21

Yes, bat roost creation like this. I've done coronet cups. I've done all boring holes for the birds and stuff like this. But yeah, specifically this precise A bat roost habitat creation and that sort of stuff. I've done various surveying for bats looking for them in holes in trees, but actually creating scratches. First time I've been

Steve Roe: 18:39

Watching Sean there do it on the ground look fairly straightforward. How complicated is it being stuck in a harness on a rope?

Mark: 18:45

it's a little bit trickier because you're using the tip of the bar and you've got to balance it and it's not. It's not the sort of cutting you make on a daily basis. It's not the sort of thing you do when you're pruning branches are cutting chunks off. So it's slightly different. On the day to day as an arborist have a it's the same techniques, it's using the sword same way but it's just slightly different to how you do it.

Steve Roe: 19:06

I'll let you get on with it. You don't see Claire Balding doing this on her podcast I'll tell you that much! So this is a BatChat first I'm 10 metres off the ground in a harness and I'm next to Mark who's got a chainsaw in his hands so Mark just describe what you're about to do.

Unknown: 19:25

I'm about to cut a big slot, either side of this oak tree 1.3 metres long down the tree about 10 centimetres wide. We're going to remove that slot lower it from the ground, cut the back off it to create habitat for neck stones habitat. So yes, I'm going to make two parallel longitudinal cuts down the stem of the tree bout 15 centimetres deep to measure my chainsaw to work out with 15 centimetres a lot easier.

Steve Roe: 20:29

So you can hear Mark is now making the final cut around the side of the tree just to the left of where he's made the front cuts and that will release a metre long piece of wood along the length of the trunk which will be lowered down to the ground we worked on the trusses nice and clean himself a nice little comfy position now set on the branch halfway up the tree. And as I'm still to watch him now there's a whole range of orange florescent jackets through the woodlands some of them halfway up trees some of them on the ground as the team works on four trees around us. The thumping noise is Mark hid in the piece that he's cut with the back of his hook, which he's going to use Mark's having to go around the right hand side of the piece because the branch that he was sat on earlier, is now in the way of where he needs to make the cut. And the cut that's been made is facing south and it's an oak tree. There's probably about 20 metres high and the cut's being made it around eight to 10 metres up and there's no lower lens on there. So true. Please get it in the bottom now it's looking quite carefully and he's got to the now. Now it's time for the final test with the axe and there's one resistant bit in the middle which is just not going to be released easily

Unknown: 22:06

At the top have you gone up above the opening?

Steve Roe: 22:24

So Jim just described the feature on the tree behind the one that Mark's working on this is for barbastelles.

Unknown: 22:31

So Will's creating one of the future roofs, it's essentially just a long slit in the face of the tree. And the idea there is that we create a split or crack type feature we created a slightly wider opening and it's tree continues to grow and callus around the wound itself. It covers over the majority of it and just leaves the small opening

Steve Roe: 22:58

Mark now it's just lowering this metre long block of wood that is cut out from from the tree he's been working on. The piece is now on the ground with Jim and Mark is just coming down.

Jim Mullholland: 23:11

I have aweird hobby!

Steve Roe: 23:20

So as the features are being brought down, they're being piled in the middle of the wood for everyone to work on. So the team have just been making cuts on the two metre long sections one for barbastelle and one for Bechstein's and Mark is heading up the tree now to the cavities currently got there to place the data logger and the top which is where hopefully the bats will be roosting and then the metre long session will be censored so it can be screwed in place so Jim is now attaching the metre long session to Mark's rope which is now getting hauled up. So in the front of Mark's, block of wood which is going back in place there are two vertical slips which have been cut to 40 centimetres from the top and bottom and on the adjacent tree. The block has had a artificial woodpecker hole drilled in using the battery powered electric drill. Woodpecker holes been designed for Bechstein's and the two slits on mastery here designed for barbastelle

Jim Mullholland: 24:46

It's one tree per day per person.

Steve Roe: 24:48

So this is first time the team have done this and we met at 10 o'clock this morning and it's now getting on for four o'clock but Jim hopes that as people return to the site and repeat the same process for other trees that the process will become faster. So Mark is now attaching the datalogger to the top of the feature. And that's it, the piece is back in place there's four screws then holding it in place. and thanks to Jim for having me along for the day. And thank you to you for listening to this episode. I hope you've enjoyed it. If you take a look at the show notes, you'll find links to Jim's social media and our other episodes on this subject. Now this series we are running back chats first ever competition. children's authors Emma Reynolds and Angela Mills have kindly donated prizes. Angela has donated a copy of Bobby the brown long-eared bat signed by both Angela and Chris Packham, and Emma has donated a copy of her newly released book Amara and the bats. To enter the competition to win one of these brilliant books. All you have to do is write as a review about this podcast BatChat. And the two winners will be picked at random at the end of the series. So there's only a few weeks left to do this. Not all podcast apps allow you to leave reviews so you can find instructions in the show notes of this episode. And please note that we're only able to post prizes to addresses in the United Kingdom. The series continues in two weeks time with the author of Bobby Brown on good bat, Angela mills. So until then, I'll leave you with a clip of that next episode. I'll see you then.

Angela Mills: 26:27

You know, Chris Packham did the foreword, which is always lovely. And Kate does some lovely illustrations. So as my first attempt, I think it's been a pretty good attempt when I go into schools and read the book. You know, the kids are so enthusiastic, and I even had one little boy say to me once, this is the best day of my life, and I thought, Wow, that's amazing.