Blood-sucking marvels: Scotland's mission to save the misunderstood medicinal leech

Join Dr Helen Taylor, Conservation Programme Manager from the Royal Zoological Society of Scotland, and Sally Morris, Conservation Officer from Buglife Scotland, as they reveal the fascinating world of medicinal leech conservation. Learn about their groundbreaking success in breeding these remarkable and often misunderstood creatures, and why protecting Scotland's invertebrates is crucial for our ecosystem.

This episode explores 'Species on the Edge', an innovative partnership programme of NatureScot and seven nature conservation charities, all dedicated to safeguarding 37 threatened species along Scotland's coast and islands.

As we navigate the historical roles of leeches, from medicine to their modern ecological contributions, this episode reinforces the importance of public involvement in protecting Scotland's unique wildlife and how everyone can help through tools like the iRecord app.

More information:
 

Species on the Edge
NatureScot - Species on the Edge
Royal Zoological Society of Scotland
Buglife Scotland
How to Make Space For Nature - Autumn Tips and Winter Tips
iRecord

Transcript:

Kirstin: 

Hi and welcome to Make Space for Nature from NatureScot, the podcast that celebrates Scotland's nature, landscapes and species. I'm Kirstin Guthrie and in each episode we'll be joined by inspiring guests who share their expertise and passion for the natural world. In this episode Tim Hancox and I chat to Dr Helen Taylor, Conservation Programme Manager for the Royal Zoological Society of Scotland, and Sally Morris, a Conservation Officer in Scotland for Buglife, about medicinal leeches and their importance in restoring and preserving healthy ecosystems. One of the rarest invertebrates in Scotland, the medicinal leech is one of 37 priority species being protected as part of the Species on the Edge multi-partner conservation programme led by NatureScot. We hear more about this important work and the efforts being made to save the species from extinction. 

So hi Helen and Sally, welcome to the podcast, thanks for joining us today. So it'd be great to hear more about your roles and how you got into this type of work. So let's start with Helen. Can you tell us a bit about yourself and the work you do, please?

Helen: 

I can. So I'm currently the Conservation Programme Manager at the Royal Zoological Society of Scotland and I look after all of our field programmes and that ranges from our work with native invertebrate species to the work we did do with beaver reintroductions in Scotland right across to international work with partners in Brazil, working with giant anteaters and giant armadillos. So it's quite a varied role and my path into the job has perhaps been slightly unusual because I did a zoology undergraduate degree and then ended up working in public relations for six years selling anything from My Little Pony to Hilton Hotels to all kinds of different products and then realised that actually I wasn't finding that particularly fulfilling and wanted to get back into conservation so I did what anybody would do and spent four months working in the Peruvian Amazon on a volunteer project with macaws and parrots and then went back to university and did a master's in conservation and zoo studies and followed that by going to New Zealand. I'd never been there before, but I moved there to do a PhD working with little spotted Kiwi, spent eight years in New Zealand, having only intended to be there for three to do my PhD, but then ended up working with lots of other bird species there and then came back to the UK for this job in Scotland. And I've been working for RZSS now for just over five years. 

Kirstin: 

Brilliant, what a fascinating path, career path and different roles there. And even the role you're in just now is extremely varied and sounds really exciting as well, actually, and Sally, can you tell us a bit more about your job and the work you do, please?

Sally: 

Yeah, of course. I'm afraid it's a bit less exciting than Helen's, but I currently work for Buglife as a Conservation Officer in Scotland. I work for the conservation programme Species on the Edge which is funded by the National Lottery Heritage Fund. So we're about halfway through this four year programme now, so I'm just two years into this job and I work on a number of different species for the programme as it's a species recovery program for 37 threatened species around Scotland's coasts and islands, and so I'm focusing on survey monitoring work to find out more about the distribution, abundance and ecology of some of these species, one of which is the medicinal leech. And as well as raising awareness about these species, I'm looking to train up communities on identification and survey techniques and provide management advice to landowners as well. And so my work here focuses on the sort of Argyll and Inner and Outer Hebrides project areas for this program. I've only been working in conservation for four years. I haven't been bouncing around quite as much as Helen, but I have worked in England, Wales and Scotland now which is all quite nice. I did a geology degree, so I've fallen into conservation. It's a bit of a surprise, but it's definitely for me. And I used to work in more practical land management, but now I'm working in a more ecological role. 

Helen: 

To be fair, Sally, you haven't had as much time to bounce around because I'm a lot older than you. 

Sally: 

No, plenty of time to rectify this. 

Kirstin: 

Sounds equally fascinating. And again, another really varied role. It's great. And you spoke about the Species on the Edge programme. And, that involves a lot of partners and communities across Scotland, and the aim of the project is to secure a future for these 37 threatened species. Extremely vital work. We're in a nature and climate crisis. So we're focusing on one of these species that you mentioned - the medicinal leech. So Helen, can you tell us a bit more about this leech and what it looks like, please? 

Helen: 

Absolutely. So medicinal leech is one of 17 species of freshwater leech that we have in the UK. I didn't know there were so many until I started working on this project. It is the largest species of leech, and it's the only one that's going to feed on mammals. So it's, people always ask how big is it? It's really difficult to describe that because it can change its shape. It can stretch itself out real long. It can be short and fat. It's a worm, right? So it can change its shape and its structure. It doesn't have a hard skeleton like we do. It's extremely flexible. It's got a sucker at either end. One end is the sucker. That's what I call the bitey end, that’s the technical term. That's the bit that they will use to latch on and feed, which, notoriously they feed by sucking blood from mammals, such as deer or cattle. And then the other end also has a sucker, but that they use just to hang on to stuff and move around. And they can also use it as a paddle when they're swimming. And one of the things that was very unexpected for me, was how pretty this animal is because you think of it as oh, it's a worm. It's a leech. There's a lot of preconceptions around the animal. But when you see them swimming through the water, they only live in really clear water so you can see them very well in that lovely clean water. They've got all these colors and patterns on them that are really obvious and you can see them using their back sucker as a paddle as they're swimming through. And so they really are quite beautiful and we also suspect that the speckled patterning that they have on the underside is like a fingerprint. It's unique to each individual and we're currently working on ways to see if we can use that patterning to tell the different leeches apart because otherwise they do all look a little bit similar to us. 

Kirstin: 

Wow, and is it right that they can live up to 20 years? Is that correct? 

Helen: 

I don’t know if anybody has concrete data on that. We would usually quote eight years as a maximum that we're aware of. I don't know, Sally, do you have additional information on that? 

Sally: 

No, I know it's been quoted, but I don't know whether anyone has specifically had a single leech that they've watched for 20 years.

Kirstin: 

I was going to say, it'd be quite hard to establish that.

Tim: 

That's a long PhD program. How long does a leech live, sitting for 20 years, waiting to finish, write up your thesis? The history of the leeches is a very interesting animal, although like you said, Helen, the preconceptions, some people might pull a face if you mentioned leeches initially but Sally, could you tell us a bit more about why the species is now under threat?

Sally: 

Yeah, of course. The history of leeches is very long and very old. So they actually, there's evidence that they were used in medicine in ancient Greece and ancient Egypt. The sort of the leech's heyday was in the Victorian era, when leeches were used for bloodletting. So this was based on a very old system of medicine, where they were used to balance the humors being various like bodily fluids, including blood. And it was thought that a balance of these humors would be essential for good health and an imbalance would result in illness. So they were used to suck blood, which is where their sort of gory public image comes from. So due to this, they were really over harvested in Europe. So they were once quite common, but are now quite rare. And although leeches used to be collected more locally, they had to be imported because of this over harvesting. But there are a number of more modern present day threats to the species. So the species is now extinct in much of its former range. And this is probably because of a loss of habitat, suitable habitat for the leeches potentially due to changes in land use or changes in grazing regimes, which affects the sort of availability of feeding for the leeches because they usually suck on blood of livestock or deer that's available. If fish were introduced to ponds that impacts the entire ecosystem and can negatively impact the leeches and the more sort of thing that we're looking into at the moment is the use of anti worming medicines for livestock, because as Helen said earlier, the leeches are a type of worm, so if the livestock are treated and then the leeches feed on them, they will just die. So there's a number of things that impact them now, which means they're very limited in their populations, and so in Scotland we've only got three sites now but they used to be a lot more common. 

Kirstin: 

And just to confirm, they're not used in medicine anymore, are they? 

Sally: 

No, there is a different species of leech, so it's illegal to use our current species of medicinal leech for anything used in medicine nowadays due to this over harvesting and how threatened they are. But there is a different species, a very similar one from the Mediterranean, that is used in medicine for a more legitimate scientific role. So they're actually used in reconstructive surgery. So if someone got a bad burn and they had some tissue that needed to be attached to repair their skin these reattached tissues can fail quite easily due to a congestion of the blood and actually, leeches have anticoagulants in their saliva, so if you put them on the reattached tissues, they can make sure that blood flows freely through the tissue, and it's less likely to fail and allows all the veins and things to repair themselves while they're sucking, but so this is still used in the NHS, but it's a different species of leech and more legitimate than the Victorian bloodletting.

Kirstin: 

Yeah, absolutely. Now that's really interesting and there is a, obviously, a bit of a gory history there, and, very timely that we're recording this actually on Halloween. And, I'm just thinking about where can they currently be found? Helen, obviously there, Sally mentioned three sites there in Scotland. So where can they actually be found? 

Helen: 

So medicinal leeches currently have a restricted distribution in the UK. There's a handful of sites in England and Wales, but here in Scotland, which is obviously where the Species on the Edge project is focused, there are only three known sites for medicinal leeches, so that's extremely restricted distribution. Those sites are quite far away from one another. So there is one loch on Islay, which is an island off the west coast of Scotland. There is a series of three lochs just near Oban, which is also in the west of Scotland. And then recently a series of three ponds in Dumfries and Galloway just last year was found to contain medicinal leech. And you can see there that you've got all of your eggs in three very small baskets in terms of the leech population in Scotland. And so if anything happened to any of those ponds, or there was any kind of pollution or habitat change, or there was just a bad year for food in those lochs for the leeches, for the medicinal leeches there, then that could have a catastrophic effect for Scotland's medicinal leech population. And with all of the species, that we work with at the Royal Zoological Society of Scotland and also that are involved in the Species on the Edge programme, a lot of these species have gone down to such low numbers that it's really important that we act now because they're all in very risky precarious situations. It's not called species on the edge for nothing. And, that, that is where we find ourselves with medicinal leech as well. 

Tim: 

Helen, you mentioned the recent discoveries of the three locations in Scotland that they exist. I was wondering, Sally, could you let us know what this means for the species? It sounds like it's good news that we've discovered that they are at least here in, in a few locations. 

Sally: 

Yeah, absolutely. As Helen said, we just discovered the site in Dumfries and Galloway last year. And this discovery is really important and we hope that we can find some further sites in Scotland as well in the future due to the low number of sites and the sort of vulnerability of the species. Buglife and the Royal Zoological Society of Scotland are working together to deliver a medicinal leech conservation breeding program. So we've been to one of the sites already and we've collected some leeches and they now live in a specially designed facility at the Highland Wildlife Park in the Cairngorms and so we're hoping to breed them and release them back into the wild in order to boost their numbers. And yeah, it's going very well, and I'm quite jealous of all the people at the park. They get to look after the leeches and see them every day, it's very cool. 

Tim: 

It's not a sentence you hear every day. I'm jealous of the leech babysitters. And Sally, do you have an idea of where in Scotland you're hoping to release back into the wild the releases that you do manage to breed?

Sally: 

So Helen might be able to help a bit more with this. There's been a big search in the last couple of years for receptor sites. So that's the name for sites where we might be hoping to re release the leeches. We are actually very pleased to say it's hot off the press that the leeches have successfully bred. So I think there's 20 baby leeches out of the park which I have seen, and they're very sweet. So yeah, we're hoping to release these maybe next year, so 2025, but I'm not sure. There's been a chosen site yet. I think it might be used to boost numbers in an existing site or nearby, but we're still trying to find the perfect place for them.

Helen: 

I think the thing with leeches is that they're quite fussy in terms of what their habitat requirements are, so they, you need a lot of conditions to be in place for a site to be suitable for this species, and that's possibly one of the reasons that they're as rare as they are, because those specific conditions don't exist in that many places. So you need good clean water. So having medicinal leeches in your loch is a really good indicator that the water there is clean and lovely and doing really well. And it's a healthy ecosystem. You also need rocks around the edge because that's where the medicinal leeches are going to lay their cocoons, where they put their eggs for reproduction. You need amphibians in that water because the baby leeches are going to feed on tadpoles and frogs and baby frogs, things like that. And then you also need livestock coming through, whether that's deer or cattle but as Sally mentioned, the cattle can’t be wormed because that would be a problem and that's a very specific set of things. It also needs to be relatively shallow lochs. So that the temperature is warm enough for the leeches to stay active and do what they need to do. And so I know Craig MacAdam, who's the Conservation Director at Buglife has been doing a lot of looking around and site surveys. And Sally and I have helped with a couple of those to try and identify sites that might be suitable. For leech reintroductions and planning a reintroduction is a really involved process. If you look, there are very well established guidelines from the IUCN Conservation Translocation Specialists Group. And we actually have our own guidelines in Scotland from the National Species Reintroduction Forum that are based on those guidelines as well. And so a species reintroduction is not a case of just breeding some animals and then popping them back out somewhere that looks like it might be good. There's a huge amount of work goes into that process and so getting the breeding program going is the first step and we're absolutely stoked that we've had that success this year because sometimes it can take ages to get a species to breed in a captive setting and so we're really pleased with the work that's happened there. But the releases will almost certainly also involve consultation with landowners, with stakeholder engagement with the public because conservation is very much about people and working alongside people. And so you need to have people on board before you conduct a reintroduction of a species into a new site. And so that's all part of that piece. So it's, it sounds like yeah, we're going to do a reintroduction and we're going to release some animals and it's going to be great. But if you look at any of the reintroductions that have happened in Scotland, whether it's beavers, the Scottish wildcat program that's going on at the moment, the work that we do with invertebrates involves an enormous amount of work in the background before you can, open the box and let those animals out.

Tim: 

That's such great news that the breeding has been successful this far. Is it easier to breed leeches than mammals say or some of the species that are well documented with having difficulties such as pandas or whatever else it might be. Is it slightly easier to breed something like leeches or equally challenging?

Helen: 

I think there are different challenges. And I think one of the biggest challenges we face with our invertebrate programs, especially when you're working with really rare invertebrates, is how little information there is on that species. So if you're working with a mammal, you've got a fair idea of how their reproductive system works. It's very similar to ours. So we're really lucky to have an excellent vet team at both of our zoos at Edinburgh Zoo and Highland Wildlife Park. And if the vets need to know something about what's going on with the mammals, they can go to the scientific literature and there'll be loads and loads of information. If something happens with our leeches, they go and look in a book and there's like nothing, or one line. These animals have such a completely different life history to anything that's familiar to us. It's very alien. Leeches are hermaphrodites. They have both male and female genitalia, which is up by their faces, the obvious place to have your genitals. But although they've got both sets of genitals, they can't self fertilise. Some animals that are hermaphrodites can fertilise themselves. Leeches can't do that. So you do need two leeches to exchange gametes. And, so we didn't know exactly what we needed to do to promote mating. So the first time we saw mating, we were really excited. We were also like, is that mating? What is happening? We're videoing the animals all the time so that we can get an idea of what's going on. And then we knew that they were going to lay these cocoons that they would put their eggs into. So it's very cool. They're actually really good parents who exude this slime out of their body and then reverse back out of it, and then the slime hardens into this kind of little tiny sponge, and then they lay the eggs inside the sponge to keep them safe. But we didn't know exactly where in the tanks that we have them in they were going to want to lay the cocoons, so a lot of what we do is about giving them options and letting them tell us what they want. So we've got a lot of my team at Highland Wildlife Park have done a really good job of setting up like bits of rock and like floating islands of bark with moths in and just to see what they would use. And then after that we weren't even sure what was going to happen with the eggs hatching. We were like, okay we think there might be like 10 eggs in a cocoon. Are they all just going to burst out together and we'll just have all these baby leeches everywhere, or are they going to come out one at a time? And it turned out that they actually will hatch out and then live in the cocoon for a little while. So we've got a really nice video of a baby leech sticking its head out the front and then being like, nah, and going back inside the cocoon and hanging out for a few more days. So every stage of that was a mini success because we didn't know what was going to happen and whether we were going to get it to work. And every stage of that is also an opportunity for learning and collecting data that will help us breed more and more of these animals, because obviously 20 is fantastic, but we would like to have more. And so we will continue this breeding program as well to try and produce as many medicinal leeches as we can. So it's a massive learning curve, but it's a really exciting thing to be involved in. 

Kirstin: 

Wow, it's such a lot of hard work that goes into the whole process and obviously you are both extremely fond of the leeches and I'm sure we would love to see them too. But for the general public, is there a bit of a fear of, for instance, cold water swimming? Is there anything to be fearful of with these leeches in the water? I would presumably think not, but I just want to ask the question. 

Helen: 

I actually do cold water swimming myself. So I'm part of the cold water swimming community. And I think that certainly at the moment medicinal leeches are at such a low density that your chances of encountering them are almost zero. We do get a lot of people saying, oh, there's this loch that I tell people not to go swimming in because it's full of leeches. And actually what will be in there will be horse leeches, which is a completely different species, its jaws aren't even strong enough to bite a person. So although you might see them, they're not interested in you and they're not going to latch onto you. I think that question is why I was talking about engaging with local stakeholders and talking to communities before you do a reintroduction. And so I think fostering that understanding, especially when you've got a species that people might be naturally fearful of, or not sure about, or just not familiar with, and helping them understand what that species in their local water body would mean for them is going to be so important. Because there isn't anything to fear, they can't really hurt you. I do understand why people might be slightly fearful or nervous about having a slimy worm attached to their skin for several minutes while it feeds but actually that's not going to harm you at all and, and you are far more dangerous for the leech than it is for you and that's the case with so many of the species that we work with. But I think, yeah, that process of consultation and talking to people and a lot of the education work that Sally's doing as part of the Species on the Edge project is really important for that as well. 

Kirstin: 

Yeah, absolutely. Education is key. As you mentioned before, we can see it with all the other reintroductions that we've been involved with. And rewilding, reintroduction of other species to Scotland that lots of people are interested in and they do want to know more and they want to become educated about these species. But Helen, can you tell us about perhaps the less well known or less publicised species that you're involved with. 

Helen: 

Yeah, absolutely. So RZSS has really grown its investment in invertebrate conservation over the past five years and we now run breeding for reintroduction programs for several invertebrate species. So pine hoverflies is probably our longest running and most successful project to date. Dark bordered beauty moths which are also up in the Cairngorms. We've been running a program with pond mud snail breeding for reintroduction at Edinburgh Zoo for reintroduction into the Pentland Hills, just off of Edinburgh since 2018. And, obviously, we have the medicinal leeches now, and we ran a pilot study to see if we could do conservation breeding with blood-red longhorn beetles this year as well, which is another critically endangered species that's just restricted to the Cairngorms. And the thing is these species are so overlooked because they're small or because people don't pay as much attention to invertebrates. But they are also crucial to the ecosystems they live in, whether that's, as a pollinator, as a waste recycler, as part of a food chain. Although we don't notice these species, we will notice when they're gone because they're breaking links in these really complicated ecosystems. And as you lose them and you lose the roles that they're playing in the ecosystems, those ecosystems will start to fall apart. So I always say to people that if you want the functioning ecosystems to do the releases of the big fluffy species, like wildcats, which we also work on at RZSS, which is a fantastic project, you do need to be looking at the other end of the scale. And it's important to not be ignoring either one or the other because they're all working together. And that's why I've become really passionate about working with the invertebrate breeding for release programmes because it's just so key to having healthy functioning ecosystems.

Tim: 

Sally, could you let us know about some of the other species that you're working with? 

Sally: 

Yeah, of course. So out of our 37 species we work with as part of Species on the Edge, I work with two more. So I work with medicinal leech, and then I also work with the short-necked oil beetle and the northern colletes mining bee. So these are two species that are associated with sand dune systems and machair grassland in the Hebrides. And so machair it's a Gaelic name, meaning fertile, low-lying plain, and describes a sort of mosaic of grass and habitats that you can find, particularly in Western Scotland, but also North North Scotland, Western Ireland, and it's a really remarkable habitat that has a wide range of flowering plants, and it's absolutely beautiful in the summer, and formed because of the calcareous sand being blown up onto the grassland. It's a habitat that's very popular with invertebrates and waders, hugely important for pollinators and for local communities in the Hebrides as well. So these two species, I do a lot of survey work for them and raise awareness of them. The short-necked oil beetle was a species that was presumed extinct, or we didn't, we hadn't seen it since 1948. And then it reappeared on the Isle of Coll in 2009, and since then, it's been cropping up in all sorts of places and it's my job to go and look for them. And they're very interesting species because they're related in that the short-necked oil beetle is a nest parasite of the northern colletes mining bee. And what that means is that when the beetle larvae hatch out and these are tiny little, they look like louse or lice, so these are tiny little things, about half a millimetre long. So they hatch out and they climb up onto flowers. Their aim is actually to wait for a bee to come by, a solitary bee. So then when the solitary bee lands on the flower, they will latch on with their specialised little hook like feet. And their aim is to actually get carried back to the nest burrow of a solitary bee because they want to eat all the nectar and pollen in there and they want to pupate in there and turn into an adult beetle. So there's lots of very interesting work over there. Potentially this is how they're being transported around the Hebrides or they've just been overlooked before. It's quite easy to overlook invertebrates if you're not looking for them. But yeah, really interesting work and there's a lot of different other work within Species on the Edge and I get to work with all sorts of different partners and communities as part of this work. It's incredible. 

Kirstin: 

Great. Yeah. And, we're always trying to encourage our listeners to, to take action to our Make Space for Nature campaign and messaging. And obviously, you spoke there about even spotting certain animals or insects or invertebrates and that's a really important part of what our listeners can do. What do you think is the best way for them to help the medicinal leech as well as the other threatened species? I'll give that one to, to Sally. 

Sally: 

I think just get involved and talk about it. Particularly for leeches, if you have seen a large leech in any sort of shallow ponds or lochs, please get in touch, ideally with a photo. As Helen said earlier, these may well be horse leeches. Horse leeches are a much more common species of leech in Scotland, but if there's been some large leeches that potentially have been interested in you, or attached to you please let us know. We've already received a lot of emails from members of the public about it and people I've talked to at events. Even if people are slightly scared of leeches, they always want to talk about them because they're fascinating. And yeah, some people have talked to us, said, Oh, Oh, I used to swim here as a child in the 70s or 80s and I had leeches attached to me. Let us know, please, because we are following up on these leads and we're hopeful that there are more sites around Scotland. And if you do live around Scotland's coasts and islands, please get involved with the Species on the Edge programme. We have a newsletter, which you can sign up to, which will tell you more about events and volunteering opportunities and how to get any management advice if you're a landowner. And, otherwise, there's a lot of recording schemes for invertebrates, there’s obviously a lot of species in Species on the Edge that aren't just invertebrates, because I work for Buglife, I'm gonna be biased and encourage you to go and look for recording schemes. And just record what you find. There's a very useful app called iRecord, if you're not used to recording things before, but if you see anything and you think that's interesting, snap a photo and put it up on there. Because a lot of these things, especially where I work in the Hebrides, a lot of species are super under-recorded just because people aren't letting us know and they think, oh, that's a nice beetle. Actually, it might be quite a rare one or an interesting one. And I've already had things sent to me that have discovered new genuses of things in the Hebrides just because they're so under-recorded. I don't know if Helen has anything to add for your species. 

Helen: 

I would echo what you said, Sally, and I think that, one of the strengths of the Species on the Edge project has been discovering new populations and the fact that, you'd asked people to look out for medicinal leech and then this record pops up in Dumfries and Galloway and, these things can be really overlooked. I think the short-necked oil beetle is another really good example of that, like presumed extinct, but was there the whole time and we just didn’t know. And if we don't know that stuff's there, it's really hard for us to protect it and conserve it. So having eyes on the ground and we have millions of eyes potentially on the ground in Scotland every day. So if people are looking out and are able to record these things and raise the alarm that they might be there. That's fantastic because yeah, we can only protect what we know about. 

Kirstin: 

Yeah, absolutely. We always talk about citizen science and just getting involved and even getting out and just noticing nature more as well. It's so important. And that's when you actually see things, isn't it? And that's when you can record and it all just leads to more of this important work that goes on. That's great. Great advice. Thank you. 

Tim: 

What might be a silly question, but the history of the leeches and being used in medieval times, is there, and for bloodletting and whatever else they used it for, was there any actual medical reason why that may have worked, or was it just a theory of the time that didn't actually help at all? 

Helen: 

I am no historian, so do not quote me on this. This is a history question, not a zoology question. But I think there was a lot of, if you look back through history, there was this whole idea about the humors, that the body had these different humors that were, and this is before people understood what the circulatory system was, that your heart was pumping blood around your body, all of this kind of stuff. So this was all the best sort of “science”, that was available at the time, and it wasn't particularly accurate, but this idea that you had different humors in your body, and if you had an imbalance of your humors, like too much of one or too much of the other, then you might be making yourself ill. And so I think this idea of bloodletting was about letting some of those imbalance tumors out and that would help balance the system and make you better. There may have been instances where coincidentally that somehow helped because there was something else going on, but there are almost certainly instances where that would have ended up being really harmful because someone who's really ill and weak definitely can't afford to lose a load of blood that to help carry things around their body and make them better. So I think any sort of benefits would have been inadvertent rather than science-based. But I think what's really interesting is the stuff that Sally was talking about earlier, where we know that leeches can be beneficial for medicine. And, she talked about the burns, restoring blood flow to amputation sites, draining hematomas, there's a lot of applications, and in veterinary care as well, where leeches can be really beneficial. So they were onto something, but just not quite, they hadn't got quite the right vein there. And it was more sort of a chance than science happening there, I think. 

Tim: 

Sorry, I just remembered the old episode of Blackadder where he gets prescribed to eat a bunch of leeches by a guy who owns a massive leech farm.

Helen:

Yeah, as you would, right? To make money. But we think about the bloodletting, so when we had a story about the leeches in The Guardian, off the back of that we got lots of people getting in touch with us about stories of their relatives who, it really does strike a chord with people because they'd be like, yeah, my, my great grandma was a leech lady and she used to go and collect them, but they were talking about people boiling down leeches in a big pot and then using that to make a poultice that you would like stick on a wound because leeches were just associated with medicine and healing. And again, that probably had almost no benefit whatsoever. And goodness knows how many leeches were boiled down to, to make these compresses. It wasn't just the bloodletting, they were just associated with medicine and healing and the trade was massive. The number of leeches that were exported and transported around the world was absolutely phenomenal. 

Sally: 

That was just like millions that went through Paris a year, absolute, yeah, absolute carnage and all these poor leech ladies that traditionally went to go collect these leeches and got horribly anaemic while collecting all these leeches. Yeah, I think it was just a craze, wasn't it? Yeah, it was a craze. 

Kirstin: Yeah. 

Sally: 

If it's been around, if there's evidence from ancient Egypt and the like, then it's just more of a this is what we've always known, leech is a good medicine and we should use them in all sorts of ways, including crushing them up, which is a shame.

Tim: 

Brilliant. Thank you so much for coming on. It's been wonderful to hear from you both and the incredible history of the medicinal leech and hope still that we can, we probably don't need the millions and millions that we had during the height of the leech trade. But it would be nice to get those numbers up and great that they exist in Scotland.

Helen: 

The more leeches, the better I say. 

Sally:

Yeah. If you haven't seen them swim, it's something else. They're like eels. They're very elegant. 

Kirstin: 

Great. Thank you very much. Thanks for listening. If you enjoy Make Space for Nature, please follow it on your podcast app and leave a review or rating. We'd also love you to tell more people about the series. For more ways to connect with and help protect Scotland's natural world, go to nature.scot.