S1E11 Despite a number of our bats using trees as roost sites, we know surprisingly little about how bats use trees. In this episode Steve sits down with veteran tree expert Jim Mullholland from the Arboricultural Association and discusses what we still don't know about the ecology of bats and trees. Jim also touches on a project he's been working on recently using trail cameras as a surveillance technique to help understand this subject.
Jim has a YouTube channel with a number of videos of bats inside tree roosts. You can view that channel here: https://www.youtube.com/channel/UCcxgmE0Z3NAW3n1yzTPohpA
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Hello, and welcome to BatChat the podcast from the Bat Conservation Trust. I'm Steve Roe. And as we head towards the end of the first series of BatChat this week, we're hearing from Jim Mulholland on the subject of bats and trees. This interview was conducted at the National Bat Conference back in September 2019.Jim Mullholland:
Are you going to let me know when I make a mistake?Steve Roe:
No! So we've just come out the first session at the National Bat Conference 2019. And Jim Mulholland has just given a talk about bats in trees. So I've just grabbed him, Jim, for people at home who don't know about you, can you just give us a bit of background to yourself how long you've been doing that work? Which bat group are you from, and do you work with bats for a living?Jim Mullholland:
I've been working with bats for the last 14 years. I started my career in ecology and I got a little bit fed up of the late nights and the early mornings. And I remember vividly waking up at two o'clock in the morning, dragging myself out of bed to do a dorm reentry survey and thoughts is this it is this is what my life is going to be in a. And so I decided to leave ecology I decided to retrain in arboriculture. And then I went to work as a tree officer for a while. And more recently, I worked for two charities one the Ancient Tree Forum, which combines my knowledge of ecology and trees, as well as the Arboricultural Association where again, it's mainly trees, but we do a bit of ecology, including bats as well. So no, I used to work with bats, but not really anymore. Apart from the occasional training course I belong I think I've gone to bat group so I belong to the Avon bat group and the Wiltshire bat group. However, I'm not unfortunately for my sins not very active with eitherUnknown:
We'll keep that bit quiet! So why trees, what's the fascination?Jim Mullholland:
Well trees trees are incredible. We taught we're here to talk earlier about how bats are incredible. And I completely agree with that. And I've always had a fascination with living things. And it started with mammals. They're the kind of more iconic species in thinking about the lines. And really kind of fantastic species are that and it then focus down on bats, largely due to my wonderful wife, Laura, who got me into bats when we were studying at university. And it led on to trees really just because they're the bottom of the ecosystem. They're the kind of the fundamental driving factors, we wouldn't be here without trees. My passion now is old trees, ancient and other veteran trees. And they provide the habitat for such a wide range of species. You know, in particularly, we're talking about wood decay, funghi, mycorrhizal fungi, and a range of SAP resilinc invertebrates that live on decaying wood. But of course, they provide homes for bats, other mammals as well. And so if you're interested in bats, you have to be interested in trees as well, because we wouldn't have the bats without the trees.Steve Roe:
So for people listening at home who don't know much about bats roosting trees at all, can you just give them a quick crash course it's so the ecology of bats centuries, if there's such a thing as a quick crash course in that,Jim Mullholland:
How long have you got Blimey? Okay, well, we have 17 species in the UK as most of the listeners will hopefully know. As far as I'm aware, we have 14 that are confirmed to roost in trees. And as you can imagine, the species ecology for those varies hugely. So we'll have some species that roost in trees as well as buildings and other structures. And we have some other species that roost only in trees. One of the things I find really fascinating if you take an example of to what we would probably consider woodland fish species or tree species that are very reliant on trees, we look at nocturnal bats and Bechstein's bat, and we look at locks your bat, we're pretty much looking at a species there that requires roosting in trees all year round, occasionally turns up in buildings, but on the whole, it's trees, and it's trees all year round. And then we flip across the back sides, which has been the kind of focus of my study recently. And whilst they're heavily reliant on trees for roosting in the summer months, in the winter, they appear to leave the woodlands appear to leave the trees and they go underground. So you can begin to see they're even in two species that appear to be relatively similar to begin with. The ecology is very different. And you can multiply that then by the rest of the species, that recent tree. So that's about as much of an introduction. It's not easy. It's really complex. And that's one of the reasons why it's really exciting. And if it wasn't exciting, I wouldn't be interested in going out climbing trees and looking for that. So it'd be boring otherwise, wouldn't it?Steve Roe:
So why is it that some species are so dependent on trees like things like pipistrelles? We know we'll use both trees and buildings. Why is it that some species like Beck Stein's and nachos have sort of refused to use buildings? Do we Do we have any idea why that is? Why they'reJim Mullholland:
just stubborn, aren't they? Clearly. When it comes down? Surely it comes down to the species ecology and how those species evolved and the niche that they feel within the environment. The these creatures have evolved into separate species. Because of the driving factors of that ecosystem. They find an opportunity to say, Okay, well let's move out of the trees and into buildings and a big kind of very plastic like pipistrelles, and As a result, they're our most common species of bats. And the ones that we look at so that Rizzoli in trees. Now, interestingly, we've had Nacho which is reasonably common, and we have backsides, which is quite rare. So even in those that are kind of stubborn and stick to trees, we have some that are still, you know, they do fairly well others that do perhaps less well, and there's there's going to be bigger issues there that it's not just about where they race, it's about what they feed on, when they come out at night, and all of those things.Steve Roe:
And you've just given a talk, like I said, At this year's conference in the last session, about a year long project that you've been doing, looking specifically at Epstein's paths, can you just tell us a bit more about that project and what you found from it?Jim Mullholland:
Yeah, absolutely. So, I've been looking at trees and trying to learn a bit more about how bats use trees for quite some time now. And we've been going out and basically I spoke last year, the National Bank conference, hashtag, bat calm and soaked about how difficult it is to find bats in trees. And the very first message I put up on the screen was that bat roofs are more likely to be empty than they are occupied. And if we're thinking about people who then survey trees for bats, and especially professional serving trees for bats, that's a real challenge. And that's a real issue. If we, you know, people are paying good money to send ecologists out there to survey trees for bats. So I kind of building on that work, which was initially we went out fine trees, we thought were suitable and just kept chatting, checking them until we find bats. And at the end of 12 months, we go once a month, we kind of say, Okay, well, we had bats, and we didn't and we can kind of show a bit of different uses throughout the year, maybe different species. But one of the criticisms of the data was that had lots of individual bats roosting and perhaps one of the reasons why the batteries were more frequently empty was because they're individuals, they're more transient and nomadic in nature. So what I wanted to do was focus on a maternity roost, and then study those. So we did some radio tracking of backsides back. So we found for maternity reach that we were then able to go on the following year monitor once a month again. And interestingly, through the similar trends that despite going out 12 times in the year, looking at these four different roofs, we found bats on one occasion, and that's really quite scary, really. So yeah, it's the kind of set we're working on at the moment. The next step is then trying to improve it and kind of spoke last year, the title of my talk was surveying for bats and trees, can we do better? And I posed the question hopefully raise a lot of concern among all the bat workers in the room, but mainly left it on a bit of a cliff edge and not really providing much of a solution. This year, we've been looking at using trail cameras to improve our likelihood of finding bats. I've been slightly plagued with technical difficulties. But still, despite even cameras only working for one evening, they've proved bats roosting in these three features. And there's so much more effective than sending out a surveyor for the 12 visits we did in the previous year. So really exciting times, it means we can kind of refine this slightly, one of the reasons why I wanted to come to the National Bank conference hashtag bat calm, was that I wanted to kind of share this idea with people and hopefully get them enthused and excited to go away and try this on roofs that they know of, and kind of, if we all start working on these things, we can kind of say, Okay, well, I've got this camera, or I've tried this setup, and really helped refine these things. And once we start generating that interest, the people who gently who produced the technology, that people who produced check trail cameras already must they realise there's a market for it. Hopefully they will be able to provide us a bespoke camera for surveying batteries.Steve Roe:
I was gonna say these cameras are trail cameras you use and I presume they are.Jim Mullholland:
Yeah, so they're just off the shelf. Ones that are designed largely for tracking large mammals. I think they were originally designed for hunting purposes and people could see where deer was they could then go out and shoot them later. And so there's some challenges with them. They're not designed for very quick moving small mammals. They're designed for slower moving large mammals. Yeah, so we need industry to catch up we need industry to produce us a bat trail camera, ideally will about to attach a built into it that comes on at certain time of night, etc, etc. So any camera developers out there, listen up, this will be coming in the next few years. And howSteve Roe:
easy to identify back to species levels on the footage. It's available at the moment.Jim Mullholland:
The cameras that I've had set up they've been on beckstein briefs and some of the footage depending on how the camera is focused on the roost feature itself. Some of them you can see the back and you can clearly tell it's a back signs back. But of course we have a species that's quite easy to identify visually. We have large years with a clear gap through the middle of them. I think it will work for some species so backsides it clearly works for long years, perhaps nuptials, things like that. Everything else will probably get slightly more difficult. But if we combine it with a bat detector, you can separate off species like pipistrelle, for example. Maybe even just then we'll be able to group it's a Myotis even if you can work out which species it is, but it's a step in the right direction.Unknown:
And how hard is it to find roots in trees? You know, we can get the public to find new roots in houses as part of the NBMP survey that's relatively easy. How hard is it to do it for trees?Jim Mullholland:
I think I gave a talk and have a stepped step by step process of finding bats in trees. And the first one is to buy a torch if you don't already have one, and then go and look in some trees because it can be as simple as that. And to give an example, I've been looking for bats and trees for quite a while and I realised I kept looking in cavities and I'm blessed that I've you know, can afford an endoscope and go out and I can use that to serve a cavities. And I was walking past a tree and I thought, You know what, I don't look in flaking bark enough. And I saw a piece of flaking bark on this oak tree. And I thought I'm gonna get my torch out. And I'm gonna walk up to that tree and have a look in it. And as soon as I did the fan to BBs tells roosting behind it. I've not been able to replicate that luck since then. But it is as easy as that if we don't go out looking for these things, we won't find them. And it can be done from the ground. A lot of the woodlands that I survey and a lot of the data that the my original talk was based on was from woodlands with features about maybe a metre high. And you can serve a many more of those in a day than you can ones that you have to climb. And so anyone can do it, you need a torch. And that's all you know, the kind of the basic equipment if you really get into the Combine endoscope, and you can get fairly cheap ones even from the Aldi and Lidl from those kinds of supermarkets for maybe 5060 quid. And if you get really into it, you know, the top spec one is only maybe 350 400 quid. And once you find that first bat roost, that's it, you'll be hooked for life.Steve Roe:
And what's left to find out what's the one thing you would like to know that we don't at the moment.Jim Mullholland:
I don't think I could pin it down to one thing that we'd like to know, the main thing that drives me is that I want to increase the efficiency of our surveys and the efficacy of our surveys that people are willing to pay for surveys either because they're forced to for development purposes or professionals working in the arboricultural. Industry, they are interested in this what the challenge, the challenge we face is that if it's not cost effective, they won't do it. And so my main drive is really not about what we want to find out, we want to improve our surveys. And if we can improve our surveys, it means we can conserve bats. Because once we know they're there, we can deal with them. The issue at the moment is that we're losing roofs, it must be on a daily basis during fairly standard arboricultural forestry operation. And it's not kind of a slur on that industry at all. It's just the fact that we haven't given them tools to be able to serve those those trees effectively. And that's because we don't know enough. So once we get our house in order, and once we can say this is how you survey trees for bats, we can pass that on make it nice and simple for other professionals. And then we can conserve bounce.Steve Roe:
More often than not trees will be unoccupied. unoccupied. Trees naturally for down rots and features are lost all the time. And that combined with the fact that the bat species reliant on trees are so transient does it actually matter that the tree disappears,Unknown:
there's so there's a couple of things there that, of course, these are dynamic structures, they evolve and they change constantly. They're not like buildings or underground structures that remain fairly static and don't change much over time. The decay features the rot etc. in trees, or one point won't be suitable they're intact would at some point, then we get some action that's started static a process off and it's a continuum it's succession and eventually that will be suitable for bats. And then as that continues, it won't be suitable anymore or become suitable for a different species about and it might be that it becomes unsuitable because it fell over it might just be that the decays advanced so much that it's too large and airy now or just completely, you know, too cold, too hot, too wet to drive about. So they are dynamic. One of the one of the big challenges it faces that is knowing which ones are important as well. So last year, I kind of shared an analogy, which was kind of the idea was given to me by a friend of mine, Keith Cohen about that rooster like chairs, and I talked about how I've got 19 chairs at home. And some I use every day. And some are really important, like the chair in my lounge or my office chair, and others, like my garden chairs are as useful and I only use them for a set period of time. Over the summer. If I lost one of my garden chairs wouldn't really bother me that much. If I lost the chair that's in front of my TV that would have a significant impact on my life. How would I watch Netflix otherwise? And so how do we know when we're losing that chair in front of the TV compared to a tree in the garden? Or how do we know when you've lost so many that they can't just hop to the next room? So it is a question I get asked I spoke at a the OB national conference a few years ago and I got asked that exact question. And it's we just don't know where that tipping point is at the moment. So the other thing is that we need to improve the way that we can mitigate for the loss of these tree roots either as they naturally degrade or when we're losing them to development or kind of other pressures. And at the moment, the tools we have available a lot. They're kind of suitable for the built environment so we can build things into new buildings. We can put back boxes up And the bat boxes kind of work on trees for some bat species, but they don't work for all bat species. So we need to start researching and investigating ways that we can begin to create these reefs features, not only immediately, but perhaps in you know, start this process off so that in 1020 years time feature start developing. And that then becomes sustainable. Because without that kind of planning, and that kind of action you might have, that's for the moment, but you will lose them over time one of the woodlands that we study, the one in Wiltshire and Trowbridge is as fantastic as a number of roofs, which are about maybe a metre off the ground, like 45/50 roosts that are that high. And what we think created those was that during the war, there was a fairly high stocking density of horses, and they would damage the trees. And then you know, 50 60 70 years later, those features have developed significantly that they can support roosting bats. And that's great for now. But we're not, we don't have that pressure on those trees anymore. That pressure on the young trees. So what happens in 50 years time or in 100 years time. And so we need to start thinking that kind of that longer timescales, I work for part time for the ancient tree form. And one of the big things we talked about when we talk about old trees is that, you know, we have to plan in the long term, my colleague who works at a site, near slough and burn and beaches, he has a 500 year management plan, because that's how long it takes to grow the next generation of veteran beech trees. And that's the kind of thing that's the timescales we need to be thinking on. My former boss at the ancient tree forum is working on a your wide virtualization project, which is largely focused on funghi, and invertebrates, but they're damaging trees to see whether they can start generating that habitat with tools rather than than with time. And interestingly, they, as they, despite the beam focus on funghi, and invertebrates, some of the wounds in the trees and some of the cuts in the trees, maybe about 30% of one particular type, they found bat droppings at the bottom of it completely inadvertently. And so I'm having conversations with her at the moment about whether we can say okay, well, we know the kinds of features that bats use, largely thanks to the work of the battery habitat key, and the parameters of those and how big they need to be and maybe how high off the ground they need to be. can we replicate those by damaging the tree mechanically with tools? And so yeah, that's kind of one of my next projects I'll be working on.Jim Mullholland:
Trashing trees, trash!? is called Veteranisation. Thank you very much! It's scientific.Steve Roe:
And if you had to choose just three words to describe the bat conservation movement, what would they be,Unknown:
Exciting is the first one, I wouldn't be working with bats if it wasn't exciting. My colleague talks about ecology in the using analogy of when you're walking in a woodland and you kind of find a thread hanging from a tree and you pull that thread, and then suddenly, a bell rings somewhere else in the woodland, you think is completely unconnected, they're actually connected. And we'd need to work out kind of why that is. And that's just fascinating US size. And that's, that's what it's all about. And we've kind of is really exciting and means that there's always something new to learn. And yeah, and just keeps me interested in it really. Second one is inclusive, I would say at the moments when I started 14 years ago, that was a little bit clicky, I had to travel an hour to go and train in Wiltshire, with a fantastic group there that were welcoming to new people at the time. And it kind of gave us that kind of foothold. And once we got the licence, we can then kind of spread that elsewhere. And I think it's improved significantly with the advent of social media, because people are much more willing to share things rather than keep it private. But it's also for me, there's kind of two key people that have really pushed that forward. And that's a good friend, Daniel Hargreaves, who's just one of the best people I know who's wonderful, very knowledgeable about bats, but he will share it as well you go around and share that information. And once you kind of start that process of one person sharing it, everyone else kind of follows on and the other one is Henry Andrews, of course, the kind of the great mind between their bachelor habitat key because he's suddenly just gone for this is what we know about bats and trees. And it's it's freely available and all that information is there and put it out into the public domain. And he's encouraged other people to go on and start studying bats. It was him that really gave me the kick to start studying bats injuries. And then final one, I guess, would be uncertain. Where in uncertain times, kind of politically, is the Big B word, which I won't mention at the moment. We're potentially a month or so away from crashing out of, of Europe. We don't know whether that's going to happen on that day, or it's going to change then we had heard from Kitt earlier that, you know, our hopes are that the legislation will be maintained as it is at the moment, but we don't really know what that will be. But uncertain, it can be positive as well. With the ancient tree form. We're kind of cautiously optimistic that if we leave the EU and we kind of then part ways from the Common Agricultural Policy that we there, maybe we're heading towards a system that at the moment is termed public money for public goods or public services or something along that line. And hopefully that will have recognition of the value of trees in a farm landscape. Because at the moment, farmers are kind of dissuaded from having trees because it's subtracted from the area calculations, which means that they clear foreigners, the trees, and that has a kind of a massive impact on a wide range of ecology. So if we can get it enshrined in that guidance that you know, we need more trees, that's good for bats as well as all the other species.Steve Roe:
Jim Mullholland, thank you very much.Jim Mullholland:
Hashtag NatBatConf.Steve Roe:
And my thanks to Jim for taking time out of his day to sit down with me for that interview. Jim also has a YouTube channel of various clips of Batson trees. The link is in the show notes below. Next time is the last in this current series of Bat Chat. And we'll be hearing from the team on the national debt helpline, as well as some back carers discussing the challenges of backcare. And the role that rescuing injured bats plays in conservation. We'd love it if you shared this podcast with your friends on social media. Our hashtag is that chat and where you can please do leave ratings and reviews in your podcast app.