Reintroduction: Bringing Species Back

Saving species from the brink and adding them into existing environments to alter ecosystems
09 August 2022

Bison in Blean Woods

Bison being released into the woods

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Last month saw a first in the UK: Bison were released into a woodland in Kent. An animal of this size and nature hasn't be known to be on UK soil for milennia, but now conservationists hope they can act as ecosystem engineers and help protect our woodlands. We explore how the European bison is able to exert such dramatic effects on its environment as well as dive into past reintroduction sucess stories, including the flight of the red kite and the nesting of the dormouse. Plus, we address the potential costs off adding a species into a new space, how learning to live alongside predators may benefit the environment, and what species might be reintroduced next...

In this episode

Trees in a woodland with the sun peaking through

01:08 - What is reintroduction?

In efforts to save certain species or alter ecosystems, animals and plants can be reintroduced

What is reintroduction?
Chris Sandom, University of Sussex

This week we are taking a look at reintroductions. No, not when you awkwardly have to tell someone who you are again after meeting them once before: wildlife reintroductions. In order to help us better understand these events, we are joined by Chris Sandom, a lecturer in Evolution, Behaviour and the Environment at the University of Sussex...

Chris Sandom - Yeah, a reintroduction is the deliberate movement of organisms, so animals, plants, fungi, from one place to another to restore them in a place they used to occur in. So quite a simple definition, it can get more complicated around what it means by 'used to occur' and 'how recently do they need to be there?' and potentially got some confusion in the future about climate change and moving territories. Some interesting complications to an otherwise simple idea.

Chris Smith - And what's the main motivation behind doing this?

Chris Sandom - So there's two really, I think. Traditionally, it's been really focused around protecting a threatened species. So if you've got a species that's fewer in number or restricted to a small area in a place that faces lots of threats, you might want to move a few of those individuals to another place to get another population established to help the outlook for that species, help the conservation of that species. The other one that's getting increasingly more popular is restoring a species that plays an important role in the ecosystem and is normally associated with the idea of rewilding. For example, reintroducing the beaver into the UK. The Eurasian beaver is not a species under particular threat at the moment, it's classified as least concern, but it has these really tremendous impacts on the ecosystem, through its dam building behavior. It can create wetlands, which is really important for lots of other species. So you kind of get those two as two main ideas.

Chris Smith - And when contemplating doing this, what sort of checks and balances are there? Because I can think immediately of some terrible examples, when people have introduced something to an environment it shouldn't be in, and they've discovered to their cost subsequently. I mean, things like the cane toad going into parts of Australia and now wreaking havoc with the natural flora and fauna. So what sorts of things are considered when considering doing this?

Chris Sandom - Yeah, this, this is a really important question and there's quite a lot, to be honest. The guidelines for reintroductions are 72 pages long. There's an important distinction, I think, to make between an introduction and a reintroduction. So the reintroduction into that place where we know it has occurred before. Whereas the example you just gave was the introduction of a species that had no ecological history there and the ecosystem struggled to adapt to it, but that doesn't mean reintroductions are automatically safe. So there's a few things we want to consider here. I think firstly, you want to think about the animals that were going to be moved. There's a big ethical issue here. Are we moving animals that are coming from a population that can withstand their loss? Are these organisms given a fair chance of being moved? You then want to think about the ecosystem they're being released into? What are going to be the consequences? Are they going to be largely positive and going to build that resilient and diverse ecologically rich ecosystem? Are they going to fit in there well? And you know, last but by no means least, how are people going to be affected? The social economic, cultural implications of a species reintroduction. And each of those has a lot to unpack. And I think getting a risk assessment right is really fundamental for all of those things. So it's quite a lot to consider.

An image of a flying red kite

04:43 - How the red kite came back from the brink

The reintroduction of red kites to the UK has been a great success, but how did it come about?

How the red kite came back from the brink
Will Dixon

Well let’s look skyward for one very visible example of reintroduction successfully in action, which is the tale of the red kite. Harry Lewis spoke to Will Dixon, who did his PhD as part of the team involved in returning red kites to British skies in the 1990s, and he told him how to spot one…

Will - It's a very characteristic bird. It's one of the largest birds you'll find in the UK. It's got a wingspan of over a meter and it's got a very distinctive forked tail. The red kites fly by catching the wind and so they're constantly twisting and adjusting their wings and their tail, which keeps them airborne with very little effort, which makes them very efficient at flying large distances, looking for their food.

Harry - And obviously we're talking about reintroductions and this one's quite special, isn't it?

Will - It is. It's one of the first successful reintroductions in the UK and, at the time, it was considered quite risky. I mean, these were birds that were globally endangered. The project involved bringing birds from an area in the wild where they were thriving, but there were still concerns about that conservation and releasing them to an area where they hadn't lived for over a hundred years. And the worry was, has the environment changed too much? Are the reasons they went extinct still there? Is it a waste of resources? And would we be better off focusing attention on conserving the birds where they already live? The reason it went extinct was persecution. So the bird was shot. So, by the middle of the 19th century, the birds were extinct in England, extinct in Scotland, and were only found in a small population in Wales, which in the 1930s was believed to only include possibly a dozen individual red kites in the whole of the UK.

Harry - Bring us up to speed then, Will. When was the reintroduction program introduced?

Will - So, in 1989, a number of sites were identified, first of all. And the really important thing was to make sure the birds would thrive where they were introduced. So a lot of work was done with local landowners and people who lived in the area to make sure the birds would be welcome. And two sites were found. One in Scotland, in the Black Isle, and one in the Chilterns, and the Chilterns was the project I was involved in. And originally birds were introduced from Sweden and then later on, birds were introduced from Spain. In both Scotland and in England, 93 birds were introduced over a five year period from 1989 to 1994.

Harry - And at what point, as a conservationist, do you start to say this - being the first attempt to reintroduce a species in the UK - when do you say it is a success? You know, are there points along that five year period where you start to get worried that you've chosen the wrong location or that this just isn't gonna work?

Will - I guess the definition of success is the population is self-sustaining. So the population will have enough offspring that you don't need to introduce any more birds. And so you are not taking birds away from other parts of the world. And that was pretty clear fairly early on in the Chilterns population that the birds were successfully breeding. And also that the offspring were fledging and were themselves making new nests.

Harry - There was a hiccup along the way though, wasn't there? Because I know that the Swedish population had different ideas in mind to what the conservationists had.

Will - Yes the red kites are fascinating species found over a huge area and some of the birds are migratory. So, some of the birds in Sweden will naturally migrate to Spain in the winter and then fly back to Sweden for the breeding season. And in the early years of the Chilterns population, some of the birds left after being introduced and didn't come back and it's not entirely clear why. It might be that they were genetically programmed to migrate as their parents had been, or it might even be that the red kites are very social birds. They tend to go to areas where there's a large population. And so in the following years, a large number were introduced together.

Harry - And today, as we've been saying, it has been a success. It's not just been a success, it's a roaring success really!

Will - It's difficult to estimate the numbers now. In the early part of the 21st century, we reached the point where it just wasn't physically possible to visit all the nests, because the program was being so successful. So a conservative estimate would be there's a thousand breeding pairs in the Chilterns now. It's actually such a success that we're now at the point where breeding birds from the Chilterns have been introduced to other areas, including some taken back to Spain, which makes the whole story go full circle.

Harry - I've come down from Cambridge to see you. And we are sat in your garden in London, looking into the skies. Now, apart from a few airplanes, you're not gonna see any red kites here are you? And it's the same in Cambridge, I would've said. So when you mention that before red kites used to be present across the whole of the UK, are there still areas that they're not making it to, or why aren't we seeing them I guess here?

Will - We certainly should see them in East Anglia. And there are some breeding pairs in Suffolk and you do occasionally see the birds in Hertfordshire. So there's no reason why they shouldn't be here. Buzzards are very successful in Cambridgeshire. Again, it is that social nature. There's a fantastic word, which is 'philopatry'. The birds tend to nest near where they're born and there is that local effect still. And the hope is they will spread. Red kites have gone from being globally threatened and extinct in England to a situation where the Chilterns now have more than 10% of the world's population, which is phenomenal. So the fact that the UK can take part in conservation of internationally threatened species is significant, but I think more interestingly is the effect that the species have on the environment. So red kites, as a carrion feeder, will compete with buzzards, with crows, with magpies, and there is talk of Crow numbers and magpie numbers being too high. And if the introduction of red kites can help to balance out those numbers, it changes the environment. So red kites are a model in terms of what's possible with reintroductions. We can learn lessons particularly about the importance of paving the way locally to make sure that the species will be welcome, but also learning more about how species that were historically part of our natural world can enhance it by coming back in.

A beaver in the water next to its nest

10:29 - What costs come with reintroducing species?

While reintroduction can solve problems for some, it can cause issues for others

What costs come with reintroducing species?
Chris Sandom, University of Sussex

Reintroductions can be deemed "sucessful" when a species is self-sustaining, like the red kite in the UK. But is everyone delighted by this project? And are there certain populations who might have to bear some consequences when new or once-lost species are brought into the environment. Chris Sandom, lecturer in Evolution, Behaviour and the Environment at the University of Sussex explains to Chris Smith...

Chris Smith - Still with us is Chris Sandom, he's a lecturer in evolution behavior and the environment at the university of Sussex. Chris, we have heard that the red kite is being hailed as a huge success story in reintroduction. Is everyone delighted though? You do occasionally hear dissenting voices where people say, 'look, there are consequences of doing this. There are knock on effects. These animals may take livestock and so on.' Is everyone in agreement? Is it a success story or are you hearing a bit of negativity?

Chris Sandom - So in general it really has been a remarkable success. I mean, this species that's now doing better globally, but in particular, in the Chiltons and potentially a victim of his own success. So the sheer numbers that are now occurring there, you start to hear people talking about they're being great, but maybe being too many of them. One of the particular areas of conflict is around feeding them. So a lot of people want to get out, get close and connected to these fantastic birds. So they leave out meat and the animals come down and you can see dozens are circling above an area and dive bombing down and collecting these resources. But that puts them in close contact with people and there's fear around what that might mean and what it might mean in terms of stealing food. They're primarily a scavenging bird as well, but they will occasionally take live prey and there's some concern that that might have impacts on things like game birds. So they might be coming into conflict with other people's livelihoods and that often is a key area of conflict around reintroduction, especially when you get anything larger and predatory.

Chris Smith - We've heard a lot about beavers being reintroduced into various places. I think on this program we talked about that wonderful invention, the 'beaver deceiver', because the beavers were flooding the farmland that they'd been reintroduced to, which wasn't going down too well. But they were protecting cities and other things downstream from flood risks. So there were winners and losers in that respect. How is that sort of thing, monitored, gauged, and then mitigated?

Chris Sandom - When you're looking at the winners and losers of any reintroduction, you're going to have to go through your risk assessment and that applies to species and other wildlife. You can't have a situation where you always have winners, essentially because there's competition for space, competition for resources, and that's true within ecosystems and for people. The issue then comes down to when you're looking at people and the example you used, there's often a lot of focus on the mitigation of flooding downstream and actually, this year in particular, the conversation of mitigating low flows as well. So you're reducing the extremes at both ends. But that does come through the flooding of farmland or places upstream to mitigate impacts downstream. Now, how do you go about compromising there? Well, you're going to need to find solutions, which essentially even out those costs and benefits. So I know there's people out there in areas where beavers have been reintroduced, dismantling dams that are causing particular and specific key problems, particularly if they're flooding buildings and having particularly negative impacts like that. So you can put in some mitigation methods that essentially mean the people are getting the benefits, maybe some conservation societies, ecotourism opportunities, even insurance companies are getting interested in nature-based solutions to these problems. It Means you share some of those benefits out and particularly targeting those that are suffering the costs of that wider benefit to society.

Chris Smith - Something like a beaver dam is pretty easy to spot. And if you get a flood in the wake of that, it's obvious what the cause is. Are there any sorts of ways of auditing other impacts? If you've got a predatory species, a red kite or something, and it is perhaps depriving other animals in the food chain of their dinner and having a knock-on consequence, is that being looked into and checked to make sure that the best intention reintroduction is not having unforeseen consequences?

Chris Sandom - There are lots of concerns around this and the species I've worked with is wild boar. And they have a really mixed reputation. There are these fantastic wild species that cause rooting and create opportunities for more species to grow. But they're also a conservation threat and places like the Forest of Dean, where there has been a thriving wild boar population after they largely escaped, so are kind of an unofficial reintroduction. There is concern that they're having a negative impact on species of conservation concern. But monitoring nature is incredibly time consuming and can be really expensive and quite difficult to work out what is actually causing the decline. So it's, as far as I'm aware, done on quite a case-by-case basis. So you might have a particular group or interested party concerned about a specific species or group of species and focus their monitoring in response to a threat that they might see as a species or introduction. So ecosystems are dynamic, they are competitive, but we can't monitor absolutely everything or, that's going to be very difficult and we don't really have the techniques in place yet. And that's just on the ecology, that probably applies to the economics and socially as well. So other projects elsewhere look at the negative impacts of large predators on livestock and there are schemes to compensate, but how do you work out whether a sheep has been killed by a war or is being scavenged by a war for the livestock's not being looked after properly or whether it's just bad luck? You know, for all of these things it's difficult to do. But it's the challenge that we have to grapple with.

A Bison

15:43 - The first bison in the UK

What does the introduction of these megafauna hope to achieve for UK woodlands?

The first bison in the UK
Stan Smith, Kent Wildlife Trust

The advantages and disadvantages of reintroduction will have been very much have been weighed up in a quaint woodland in Kent recently, which became the home of a brand new animal, potentially never before seen in the UK. Julia Ravey speaks to Stan Smith from Kent Wildlife Trust…

Julia - <Camera Shutter Clicks> No, we're not on the red carpet at a Hollywood movie premiere. That is what it sounds like. Those clacks of camera shutters are capturing the moment bison were released in the UK for the very first time Stan Smith from The Wildlife Trust in Kent, explain to me how these animals can drastically impact our ecosystems.

Stan - Bison are amazing animals. They are Europe's largest land mammal. They are one of our last real megaherbivores that we have. And European bison can do things that no other animals can do purely by way of their size, really. And, because of this big size, they can really push through into dense vegetation. And the reason we've used bison in this area is because what we want in our Woodland is to really try to create a really dynamic and rich habitat. And what that requires is that the Woodland has lots of different structures, the trees in the Woodland are all different sizes or all different ages and the wooden has space for other plants and species to inhabit. And that's what bison do, they go in and they create space in the Woodland. They push over some trees, they crash through smaller areas of brush, and they even actually start to eat the bark off of trees. And so those trees, they start to die off. That might sound like a bad thing, but where you get one tree die off, you end up with dead wood, which is fantastic for creepy crawlies, invertebrates. And where that tree dies. Lots of new trees can grow up in its place. So it really is kind of creating a rich dynamic ecosystem just because bison are out there doing their own job really.

Julia - And who are the bison that you've introduced?

Stan - So we've started really small. We wanted to really get this right. It's a first for the UK. We have an older female and two younger females, and we've got a male bull following up in about three weeks time. There herd structures is a bit like elephants, where the older females in charge. She's the matriarch and she leads the rest of the herd around. And so we had to make sure that she was really happy and settled first, that she knew where she was going, she knew what the space was going to be like so that she could feel settled. And then the other bison come in and then just take her lead. It was amazing to watch these bison meet each other for the first time on site. By instinct, they know this is the bison that's in charge. I'm gonna follow her around and see where we go from there.

Julia - A common controversy surrounding reintroduction is about if a species is native or not to a place, what are your thoughts on this? Do we need to prove bison were here before to have them here now?

Stan - I think it's a really interesting debate and an important one. But for us, it's not the reason that we're bringing these animals in. We don't have any fossil evidence that European bison were here in the UK. Although we do know that their closest ancestors, the steppe bison, which are all extinct now, they were in the UK up to 30,000 years ago at the end of the last ice age. And so we just don't know whether European bison were here or not. But what we do know is we used to have animals here who created that dynamism in our woodlands. They were able to push through those dense areas and really kind of change things up as kind of ecosystem engineers. And because European bison are the last animal we have left that can do this. It really is kind of a no brainer. They are the alternative to these really carbon intensive human managed systems. And so this is just a way that we can start to move away from using machinery so much.

Julia - And now we have the first bison out in the UK. How are the impacts of these animals on the environment being monitored? Is there a way you're trying to compare the area of wood that they're living in to other areas?

Stan - So this whole project has been set up as a scientific trial. It's a really big Woodland, about 560 hectares, sort of almost two square miles. And just under half of it will be the bison area and the bison are gonna be in this area with actually some other animals too. They're also going to be in there with Exmoor ponies and iron age pigs, they're kind of a domesticated wild boar hybrid. Having all of these animals together, we think are going to be the absolute best kind of complimentary systems. They eat in different ways, they move around in different ways and, all working together, they can really create that kind of rich habitat. But in order to compare those animals, we needed to have a control area. And so what we have is another area just under half of the Woodland, again, that is being used with domestic equivalents.

Stan - So, instead of bison, we have Longhorn cows and then we have the same ponies and the same pigs, so that we can just test the difference between what a domestic cow can do versus what bison can do. And then we have a third area, which is our control area. In that area, there are no animals at all. It doesn't mean we won't do anything at all. Instead, we just continue with that traditional Woodland management, using machinery, using chainsaws. And that way we can compare the type of Woodlands and the way that they're managed today in the UK, versus what these different animals can bring us. What we've got are collars on the animals that tell us exactly where they are at any time. So we can track where they are. We are now monitoring, absolutely everything you could imagine. We're taking soil samples all across the site, 142 in fact, across the whole site, because of course we're gonna have all this fantastic bison dung on site, as much as anything else, which really is kind of rocket fuel for the plant life on site. And then of course we want to think about how the vegetation is changing, because as I mentioned, the way that the structures change on site, the way that the woodland will grow in different ways, all provides different opportunities for different species.

Julia - What has the public reaction been to the bison? Have people been worried because we've got these now really large animals in the wild per se in the UK, or have people been really excited and looking forward to getting involved and maybe even catching a glimpse of these animals.

Stan - It's been so amazing to see people's reaction to this project. When we first put it together, we thought this is pretty out there. You know, not many people have ever attempted to do something in conservation of this kind of scale. And so we were a bit nervous. We thought that people might be a bit resistant to wanting these big animals and we couldn't have been more wrong. People have been so excited for, I think the last two years, every person I meet says to me 'when are the bison coming? When are the bison coming? I can't wait to see the bison.' And so it's been fantastically positive. There have been some individual concerns. Most of those things come from maybe not understanding what these animals are like because people think, oh, that's a really big animal, It's gonna be really scary, maybe it's really dangerous. But actually they'll all be behind fences

Stan - So people will be kept sort of separate from those animals, so that animals can remain safe and the public can remain safe. We've in fact experienced in Holland where you can go and stand in places that have bison without any fence in between you and they're so amazingly calm. But this way we can show how we can live alongside these big, almost prehistoric creatures. And it, you know, can be fantastic for our environments and hopefully gives people a real kind of connection to nature. Something that really gives you a sense of awe around what our habitats and species are and can be in this country. And I think that's fantastic for everyone, which is a sort of chance to re-wild ourselves, I suppose, as well.

A wolf in a snowy woodland

23:59 - Could predators be reintroduced in the wild?

The animals at the top of the food chain can have drastic impacts on ecosystem dynamics

Could predators be reintroduced in the wild?
Chris Sandom, University of Sussex

Bison have just been reintroduced in the UK, which are ENORMOUS animals. Although placid in nature, the thought of living alongside big animals can cause a stir. Chris Smith asked Chris Sandom from the University of Sussex if public opinion be different if we reintroduced a species which was a bit more aggressive and predatory...

Chris Smith - Helping us out with the program on wildlife reintroductions, which is what we're talking about this week is Chris Sandem. Chris, we've just heard from Stan Smith there about the reintroduction of bison into the UK. They're enormous animals. In your experience, he did say they're placid. Would the public be a bit less receptive if we reintroduce something a bit more aggressive and predatory perhaps?

Chris Sandom - Yeah. You get real mixes of response from people. And partly it depends on where you are. I guess it depends on how close you might be living to research onto the possibility of the wolf for reintroduction to Scotland. For example, you saw a lot more positive receptions from people based in urban areas that might enjoy the idea of visiting areas which have the wolf, but don't have to live alongside it and deal with some of the consequences.

Chris Smith - Is this evidence based Chris? As in, do we have an evidence base to fall back on of people doing these kinds of initiatives, so that we can say to people, this is what's realistically likely to happen. If we do this?

Chris Sandom - There's a lot of evidence out there in many different forms. So you're never going to have perfect evidence. Every place is a bit different. One of the arguments for introducing the wolf to somewhere like Scotland is to have an impact on the deer population, which is what was seen in Yellowstone as well. So they have the elk, which is a closely related species to the red deer. They reintroduced the wolves that changed the behaviour of the elk. The population came down and then trees started growing again where they hadn't been before, but that story's more complicated than sometimes it's presented. And that's what I mean by ecology being a very complicated science.

Chris Smith - If we actually were to go down that path of doing this kind of thing, how do we know that if we do this, it's going to work in an environment? If you let these wolves go, then presumably if you get it wrong, to try and reverse things, and that might not be easy to do.

Chris Sandom - Yeah. So one of the key points in the guidelines for reintroduction is to have an exit strategy. So if it's not working, you want to have a way of doing that. As you go up the food chain that tends to mean smaller numbers of individuals. So it would be the potential for catching them up, collars, and knowing where these animals are, as Stan was describing with the bison, seems possible. But also it's about learning to live with nature and predators occur all over the world, if we make that choice.

A Dormouse

25:60 - The resurgence of the dormouse

Dormice can teach us much about the health of our woodlands, so protecting them is a very important task.

The resurgence of the dormouse
Gwen Hitchcock, Wildlife Trust for Bedfordshire, Cambridgeshire & Northamptonshire & Roger and Sarah Orbell, Wildlife Trusts Volunteers

Big predators can drastically impact surrounding ecosystems. But other species in the middle of the food chain can be important indicators of environmental success. And, local to us here in Cambridgeshire, the reintroduction of one small animal is teaching us about the quality of our woodland, and has been a big benefit for participating members of the community. Julia Ravey spoke to Gwen Hitchcock from the Wildlife trust for Bedfordshire, Cambridgeshire & Northamptonshire and went to Brampton Wood in Huntingdon to find out more from volunteers Roger and Sarah Orbell…

Julia - Ah... So is this a box waiting to go out?

Roger - Yeah, these are just some new boxes. We've got our local friendly shed group, like 'men in sheds' type groups.

Julia - Oh yeah.

Roger - This is the same sort of equivalent in Brampton on the RAF camp. And they've just set up in the last 12 months, mainly for mental health and people that wanted to do some things as well, some projects over the winter months, and they've been making these for us this year.

Julia - What I was being shown was a small wooden box. One of the many which are scattered throughout Brampton wood in Huntington, Cambridge, these boxes are designed to house a tiny rodent. The door mouth

Gwen - Dormice are really fascinating, small rodents. They are arboreal, so they live in trees. They do come down to the ground, but not very often during the summer months. They also are very fussy about what they like to eat. So they need to feed on very high energy food sources, things like nuts and berries, which people always associate them with. Because they rely on these very specific food sources, which aren't available over winter, that means they hibernate. Because of this lifestyle, they tend not to produce many young, so have quite small litter size. You tend to only get one, maybe two at most litters a year. Dormice are what we call an indicator species. So where you have dormice present, you know that you've got a really good quality woodland or hedgerow. So where we've been losing them, we know that's because the quality of the habitat has declined significantly.

Julia - Gwen Hitchcock, from the Wildlife Trust. Dormice numbers declined drastically at the beginning of the 20th century.

Gwen - So in Cambridgeshire, they went from being a species that was present and fairly common to being extinct in the wild. So a decline in the woodland management meant that a lot of woodlands got overgrown. The habitat became less suitable for dormice. We also have overmanagement of our hedgerows and hedgerows being ripped out completely during the intensification of our agriculture. And that also meant that there were less suitable habitats and also less connectivity for dormice to move around

Julia - In order to reverse this decline, an intervention was needed.

Gwen - Back in the early 1990s, the species recovery program decided to reintroduce dormice as a way to sort of facilitate getting them back into areas that they couldn't always reach. Cambridgeshire is the site of the first ever dormouse reintroduction in the UK. They got a small number, it was a mix of wild caught and captively bred dormice and released them into the Woodland over a couple of years. So in 1993, and in 1994. Following on from the reintroductions, they're all monitored. And that involves going and checking dormouse boxes every month during the summer and recording how they're doing.

Julia - And that's why I came to Brampton Wood, the site of that first dormouse reintroduction in Cambridgeshire, and met some of the volunteers who do these surveys.

Roger - I'm Roger Orbell and I'm the administrator for the Brampton Wood dormice project.

Sarah - I'm Sarah Orbell. I'm Roger's other Half. I just help with whatever I'm told <laugh> On this project.

Julia - <laugh> The boxes Roger was describing just before are crucial to monitoring the reintroduction. And they are designed specifically for dormice.

Roger - So basically instead of having the hole on the back next to the tree. We have the hole at the bottom.

Julia - Oh yeah. So it's different to the bare box where the hole will be on the front. Yeah. This one's underneath.

Roger - Yes. Yeah. So the dormouse goes and sits on the platform and then goes up through the hole in the bottom. And we sometimes have a wire mesh at the top or now we've just decided we've just changed this to perspex so that we can inspect the box without disturbing anything.

Julia - The presence of a dormouse or dormouse nest in these boxes indicate the species are living in the area surrounding it. Where these boxes live have shifted over the years to better understand how the reintroduction is going.

Roger - See that's the general outline of the wood. And they were all up in that 'Section A' originally. This is where they were released up here. We're now monitoring the whole wood, but just a single row of boxes down each side of each one of the rides. We now know that they're established in that original release site, but we just wanted to find out how far they traveled and to make sure that they are happy and dispersing in the whole area.

Julia - With many hundreds of boxes in the Woodland, it is important to note...

Sarah - They are not to be disturbed. We are only allowed to disturb them once a month on an official survey day. And we have licenses.

Julia - And while the boxes act as a good indicator that dormice are living in that area of the wood, they don't tell the whole story.

Sarah - I describe it as we're only seeing the tip of the iceberg. Hopefully, they should be in these natural underground areas and hiding in the stalls and the roots of the trees. Occasionally, some of them, you're lucky and you find it in a dormouse box, but it's a bit like geocaching, you know. You open the box and sometimes there's nothing in it. I think the best experience ever was opening one and seeing a mother and young. Okay. You're not allowed to disturb them and as soon as you realize that there are young in a box, the lid goes back on and you retreat. But just seeing it and if you've got young, you know that they're happy.

Julia - The dormice Roger and Sarah have seen seem to be very happy, but has the reintroduction been a success? Gwen Hitchcock.

Gwen - I think definitely, yeah. For long term success, you're looking for the dormice to be distributed throughout the woodland. So we reintroduce them into one small area and then we hope they move throughout the whole woodland. And also we then want to look at them moving beyond the wood to try and colonize new areas. And then at our site we've got both of these, we've got the dormice having moved all the way through the woodland. And we've also got them moving to the hedgerow through surrounding farmland.

Julia - But although the reintroduction of dormice in Cambridgeshire has been deemed a success story, we still need to protect these animals from human driven changes to our environment.

Gwen - So the big threat with climate change for our dormice is that our winters are getting warmer and wetter. And as an animal that hibernates, they need to put on an awful lot of weight to survive through the winter. Wintertime is the time of high mortality anyway. So between 40 and 70% of dormice don't make it over winter. And if your winters are warmer, they're gonna be waking up more. And if they wake up and there's no food there, that decreases their chances of survival through the winter. So we really need to do everything we can to try and make the habitat as best as it can be, to give them the best fighting chance to get through.

Lynx in the snow

33:07 - What species could be reintroduced next?

And how can we balance the potential positive impacts of reintroduction versus long-term data collection?

What species could be reintroduced next?
Chris Sandom, University of Sussex

Based on the reintroduction case studies, it sounds like a lot of these projects are long term initiatives. We’ve got to be patient, but also can’t afford to delay getting started if they are to help with climate change. Chris Smith spoke to Chris Sandom about how to handle this balance...

Chris Smith - Well back now with Chris Sandom. Chris, based on the stories we've heard today about reintroductions, it sounds like a lot of these projects are very long term initiatives where you don't see the fruits of your labors until a long time has elapsed. So we've got to be patient looking at what impact they may have. That presumably also means that we can't afford to delay in pursuing these initiatives because that would take even longer to see any benefits.

Chris Sandom - Absolutely. I think nature recovery is incredibly urgent for lots of reasons. And we haven't got time to waste, not least with climate change. But I think what's encouraging, certainly in Britain, we're seeing a lot more species reintroduced. We've got white-tailed eagle on the Isle of Wight, white storks in the south of England, pine marten being reintroduced to the Forest of Dean. So yeah, I think there's a lot of enthusiasm for it. I was actually with a class of seven year olds, not too long ago, who invited me to talk about rewilding and I've never been in with such a group of enthusiastic and knowledgeable people looking for reintroductions of the future. And they were really asking me 'when are wolves going to be turning up throughout the UK?' So if we think about them inheriting the landscapes of the future, and if they're at all representative of the wider population, then yeah we need to get on with it because these things do take time and the benefits of them take time to come through.

Chris Smith - Have we solved the reasons though that many of these species no longer have a home here in the first place? The fact that there is a lot of pressure on the countryside. There's development, there's busy roads. Do not those pressures intensify with every passing day? Really we may well try to introduce things back into an environment, but they'll just disappear again because it just can't support them anymore.

Chris Sandom - The pressures have changed in different places, in different parts of the world. If you consider Europe has a more stabilizing population, potentially decreasing in certain places, whereas others have more exotic and larger wildlife still significantly growing populations. So, arguably this is a challenge felt worldwide. And many of the species that we are thinking about reintroducing have had enormous ranges in the past and it's whatever steps we can take. With the pressures, a lot of it comes down to direct conflict with people. I think certainly with the larger mammals and these ecosystem engineers or keystone species. They're fine living with people provided that people accept them and don't persecute them directly. Roads could be the exception to that, so there are certain road densities. Where certain animals just can't cope with that because of the mortality level. But we do have places just within the UK, in all the countries of the UK, that have the potential to host a much richer assemblage of big species and smaller ones than they have for a long time. And I think that's really exciting. And I think if we challenge ourselves to really think about the future and what might be possible, it offers a lot of excitement as well as some very understandable difficulties that need to be addressed.

Chris Smith - And just briefly Chris to finish, what animal would you like to see reintroduce next?

Chris Sandom - Ooh next? Depends where you are. If we're talking about the UK, I'd love to see the wolf back here. I did a chapter on my PhD and I think the impacts they could have on the ecosystem would be really fantastic. But I think the Eurasian lynx may be a species that might have a few less difficulties and be equally exciting,

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