Saving Scotland's Red Squirrels and tackling the threat of Invasive Non-Native Species

In this episode we chat to Katie Berry from Saving Scotland’s Red Squirrels, a project led by the Scottish Wildlife Trust, in partnership with NatureScot and others, working to ensure red squirrels continue to be a part of Scotland’s native wildlife.

Katie explains more about the work involved, the threat from the invasive non-native grey squirrel, the importance of volunteering, and how we can all be part of this work.

We also meet with NatureScot’s recently appointed Chair, Professor Colin Galbraith, who digs deeper into why invasive non-native species are a major threat to our native wildlife and what else is being done to tackle them.


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Saving Scotland’s Red Squirrels

Invasive non-native species

Non-native species of concern in Scotland

Report a non-native species on iRecord



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 will help you learn more about our amazing natural world. In this episode, Tim Hancox and I chat to Katie Berry from Saving Scotland's Red Squirrels, a project led by the Scottish Wildlife Trust in partnership with NatureScot and others, working to ensure red squirrels continue to be a part of Scotland's native wildlife.

Katie explains more about the work involved, the threat from the invasive non-native grey squirrel, the importance of volunteering, and how we can all be part of this work. We also meet with NatureScot's recently appointed chair, Professor Colin Galbraith, who digs deeper into why invasive non-native species are a major threat to our native wildlife and what else is being done to tackle them.

Hi Katie, welcome to the podcast. Thanks so much for joining us today. So, everybody loves a red squirrel but unfortunately, they haven't been faring very well recently. Can you give us an overview of the history of red squirrels in Scotland and maybe explain what's been happening to the population in recent years please?


Absolutely, well Kirstin, thanks so much for having me today. It's really great to be here. Red squirrels are one of Scotland's most loved animals and they're the only native squirrel species to the UK. Their origins can be traced back to the end of the last ice age. They arrived from the south from Europe and as the ice retreated, they spread north and as woodland cover increased across the UK. And at that time, they probably would have been pretty widespread throughout the country.

However, in more recent times, in more recent centuries, deforestation and more significantly the arrival and the impact of the invasive non-native grey squirrel has caused their population numbers to crash and their distribution to seriously decline throughout the UK with only around, we think, 120,000 remaining in Scotland today, although it's very hard to put a number on these things.

The population in Scotland is the UK's last remaining core population and it accounts for about 75% of the total population across the United Kingdom. And in lots of places, even in Scotland, they haven't been seen for many years.


Katie, you mentioned the invasive non-native grey squirrels. Can you tell us more about where they came from and why they're such a threat to the red squirrels?


Yeah, absolutely. So, as you say, this is one of the biggest threats to red squirrels in the UK.

They come originally from North America, and they were introduced first to Britain during the Victorian times and in the early 20th century, often to decorate the gardens of large stately homes. And unsurprisingly, they escaped and they expanded their range very quickly, completely replacing red squirrels in much of England and Wales and much of Scotland too. They're larger, they're more robust, they can digest food sources earlier in the season than reds can.

They have a higher reproductive rate and they're also able to live at much higher densities than red squirrels. So, because of this, they outcompete reds for food and living space. They basically fill the same ecological niche, but are much better at doing so, basically, within the UK's environment.

So, grey squirrels also, some of them, harbour the squirrel pox virus, which doesn't affect them at all, but is lethal to reds and will kill, I think, about 90% of red squirrels within two weeks of catching it. So, it's really devastating to them. And when grey squirrels move into a new area, it's estimated that they will replace the red squirrel population within about 15 years. And research has shown that if squirrel pox is present within the population, this process will be up to 20 times faster.

Additionally, grey squirrels also have a detrimental effect on our native and commercial forests, which I think we'll talk about a bit later. But the competition between the two animals is a human-made problem and it's up to us to manage that and find solutions.


Yeah, absolutely. So, talking about the project that you're involved with, the Saving Scotland's Red Squirrels, can you tell us who's involved and what's actually being done to help the Red Squirrel population?


Yeah, absolutely. So, I'm part of a project called Saving Scotland's Red Squirrels, and we've been undertaking strategic control of grey squirrels in various multiple phases since about 2009. We're a partnership project.

We're led by the Scottish Wildlife Trust with other key partners and funders, including NatureScot, Forestry in Land Scotland, Scottish Forestry, Scottish Land and Estates, RSPB Scotland, and the National Lottery Heritage Fund.

We're currently nearing the end of a two-year transition phase, which has had a focus on collaborating with our partners and other stakeholders to establish a permanent and sustainable means of securing the long-term future for the core populations of red squirrels that we have in Scotland.

So, we've got several strategic areas, and we're focused on places where we know that grey squirrel control and management will have a positive impact on existing red squirrel populations.

So, one of those places is in the northeast of Scotland in Aberdeen and Aberdeenshire. And we've been working there since 2011 to reduce grey squirrel density population numbers. That population is actually isolated from the rest of the grey squirrels in the UK. They escaped from a zoo in 1971, and that population was a much later reintroduction and isn't connected to the rest of the grey squirrel populations at all. So, because of that reason, we are now aiming for eradication within that part of Scotland.

And the work that we've been doing since 2011 has been really, really successful. And we've now seen red squirrels returning to gardens and to parks in Aberdeen City, right in the centre of Aberdeen City. And we're very hopeful for the immediate future of that work.

We are also working in the central lowlands of Scotland. Our work here is focused on preventing grey squirrels from breaching the Highland Boundary fault line and entering the Highlands and Aberdeenshire which are red only areas at the moment.

So, there are no grey squirrels that exist north of the Highland Boundary fault line and that is a geographical natural fault line that runs diagonally across Scotland from Helensburgh on the west coast to Stonehaven on the east coast.

So, we're focused there on landscape scale, grey squirrel control and monitoring. And we also carry out squirrelpox testing to monitor the spread of squirrelpox from the south of Scotland up into the central islands. And then finally, we also work in the south of Scotland.

So, there are existing red squirrel populations here too, both in Dumfries and Galloway and in the Scottish borders. And as part of our last developing community action phase, we helped set up a network of volunteer led red squirrel groups who are working to protect these key red squirrel populations in priority areas across the south of Scotland.

We're continuing to support these efforts and we provide necessary professional grey squirrel control in key areas. Squirrelpox is prevalent throughout the area, but work that we have done has shown that if we keep grey squirrel densities low, it can still allow red squirrel populations to thrive in that part.

So local communities in general, local communities, volunteers, landowners play a really key role in assisting with grey squirrel control and monitoring in all of our strategic areas. So, we assist home and landowners to control grey squirrels on their own land and we do this through a voluntary trap loan scheme where we'll lend out traps to people that they can have in their gardens. And we also support landowners to access the Scottish Rural Development Programme funding through Scottish Forestry and support grey squirrel control.

Volunteers help us in lots of different ways across the country, from assisting with grey squirrel control, surveying and monitoring efforts, to helping run the volunteer-led groups in the south of the country. There's quite a lot of work that we've been doing, but that's a brief overview of what's been happening.


Thanks, Katie. That's an incredibly thorough list and pretty damning for the grey squirrels, the number of ways that they impact the reds. So grey squirrels, as you've mentioned, are classified as both invasive and non-native, but it's not just them that are the invasive species within Scotland, with many others from plants or marine life.

Can you let us know how important are projects like Saving Scotland's Red Squirrels in tackling these problems?


Absolutely, yeah. So, landscape-scale projects like Saving Scotland's Red Squirrels that tackle invasive non-native species in this coordinated and strategic way that we've been doing alongside communities are absolutely crucial if we want to manage the threat of invasive non-native species in a meaningful way and ensure really the survival of our native wildlife and biodiversity which is what at the end of the day this is all about for all of us.

The threat of invasive non-native species is estimated to cost Scotland around £499 million per year, which is an incredible figure. And invasive non-native species have been identified internationally as one of the top five global drivers of biodiversity loss around the world. So, without the work that we do over the last 14 years, grey squirrels undoubtedly would have expanded their range in Scotland and red squirrels would have lost out as a result and we would have less red squirrels in the country today.

So, we've demonstrated that with appropriate investment support and coordination across the landscape, there is the capability to turn the tide on invasive non-native species. It's not a one-way trip. But to truly do this, we need to make sure that projects like ours are prioritised and that they have longevity and sustainability built into them.

The projects need to be institutionalized and ingrained within the operations of statutory agencies, local authorities and anybody else that's working in these landscapes. Projects like ours play an invaluable role in raising public awareness as well and empowering local communities and members of the public to be part of this.

We absolutely couldn't do it without all of the support that we receive from the public. And this would be the case for any invasive non-native species project.

So, we fully encourage anybody interested to get involved and to get in touch and find out about opportunities in their local area if they're interested in the work that we're doing.


It's so important to get that point across about community involvement, and anybody can get involved with this. We've certainly got a list of ways that people can help on our website and also people can obviously get in touch with you guys direct.

The other thing about projects such as Saving Scotland's Red Squirrels, we could say it's focused on the one species, you know it's in the name, but it impacts on so many other species in Scotland. Can you tell us a bit about that please?


Yeah, absolutely. So yeah, as you say, grey squirrels, you know, affect red squirrels, and that's what they're predominantly known for. But interestingly, grey squirrels also have a detrimental impact on other species.

What I'll say is that red squirrels are really important to the health of our native woodlands. They store tree seeds, everyone knows that the famous cashing of seeds in the autumn time, which we're now entering into at the moment. They bury them in the ground with every best intention of coming back and retrieving them, but sometimes they forget and this is part of our native natural native woodland regeneration process.

Red squirrels are also fungivores, so they'll also spread the seeds of fungi, or the spores of fungi, sorry, which is also as we all now know incredibly important for our native woodlands. So, they're really key for native woodland regeneration.

Grey squirrels also will bury seeds and spread fungi spores as well. However, they inflict an incredible amount of damage on trees through bark stripping. And this is something that lots of people who have been in native broadleafs in areas where there are greys will have seen. This is because they live at a much higher density than red squirrels.

So, although red squirrels do bits of bark stripping, it's to get to the yummy sap that's underneath. Grey squirrels, the impact that they have because they live at higher densities is far, far greater. And so, because of this reason, they pose a real major risk to our national forestry goals, like increasing riparian forest cover and restoring native temperate forests.

So, if we want to expand native broadleaf and expand our native forests, then the grey squirrels really need to be dealt with as well because of this reason.


And they're quite easy to distinguish from each other, aren't they, the reds and the greys? Everybody can see it, particularly the size as well. Greys are, as you said earlier, much, much bigger. And they're such an iconic species in Scotland, the red squirrel.

We always see the interactions on our social media channels go way up through the roof as soon as we put a lovely picture of a red squirrel on our Instagram channel. But sadly, many people haven't seen a red squirrel.

They've probably, I would suggest, say most people have probably seen a grey squirrel but if they want to, if our listeners really want to go out and see a red squirrel, where's the best place to spot one?


Yeah, absolutely. Yeah, it can be such a thrill seeing a red squirrel. I still get so excited every time I see one. Anyone that I'm with is like, oh my goodness, you know, she's so excited. But I am. I think they're absolutely fantastic.

So yeah, so really luckily for anyone living in Scotland, as I said, Scotland's home to 75% of the UK's red squirrel populations. And as such, there's a better chance of seeing them here than in anywhere else in the UK.

So, if you're in Scotland already, you're doing it right. So, you can have a look at our website. We have a sightings map, a public sightings map, where people submit their sightings. And that's the first kind of gauge at the main areas where red squirrels exist in Scotland.

So, we would definitely recommend having a look on there. We also have five red squirrel rambles, which is suggested walks in places where there are red squirrel populations and people can download those from our website and via our digital app. And that will kind of guide them around areas where we know there are active red squirrel populations.

Aside from this I'd really suggest going to the Scottish Wildlife Trust's Loch of the Lowes Visitor Centre. They have a really thriving red squirrel population there and you often see them there. And there's also the Forestry and Land Scotland's Lodge Forest Visitor Centre in the Queen Elizabeth Forest Park near Aberfoyle. So, I haven't actually been myself but I often hear lots of people saying that they've been there and that they've seen them.

So yeah, those are some of the best ways as an initial guide. I would also say that dawn and dusk are typically the best time for spotting red squirrels. That's when they tend to be most active in general. It can depend on the season, but in general. And also, they feel very similarly to us about rain. So, if it's raining, you're much less likely to see them. They'll probably be curled up in their dress somewhere trying to keep cosy.


Who doesn't love seeing a red squirrel? I know I still get very excited as well, but I'm not from Scotland, so I get even extra excited. As part of our series and our campaign for Make Space for Nature, we always look for ways to encourage people to find small ways to help either with climate change or biodiversity loss.

So, what can people listening today, what should they be doing if they want to, in any way, or any small things they can do to help out red squirrels.


Brilliant. And yeah, I think it's so important to give people these opportunities and to show that anybody can help wildlife, even with, you know, five minutes or small tasks.

So, yeah, there's lots of ways that people can get involved and to help red squirrels in Scotland, no matter where in Scotland you are. One of the simplest ways is by reporting sightings of both grey and red squirrels on our website. You can do this at any time of year but we are especially looking for people this year between the 2nd and the 8th of October to take part in our Great Scottish Squirrel Survey and report as many sightings as possible during this week. You can do this from anywhere in Scotland, whether you live in the central belt, whether you live in the highlands, whichever species, we don't mind just as many sightings as possible during that week. It only takes a few minutes to do this on our website and it plays an essential role in informing and directing our strategic efforts on the ground.

So, this is one way that people can really help us. And last year we received 10,000 sightings in the total year, which was our third-highest year to date. And we'd really love to beat that this year and improve on that. So yes, please do. Every single sighting is verified by a member of staff, is looked at, is thought about. We really care about every sighting that we receive.

There are other ways that you can help red squirrels at home as well. So, if you have any bird or squirrel feeders in your garden to clean them regularly with an antiviral solution, this is to help stopping the spread of squirrel pox. No matter where you are, this is really important and we have instructions for this on our website.

You can also plant native trees or shrubs to provide natural food sources and increase the habitats for reds. This is especially important in areas where there are existing red squirrel populations. So, Scott's Pine and Hazel are two favourites.

You can also, if you sadly find any dead red squirrels, you can send these for post-mortem to the Royal (Dick) School of Veterinary Studies in Edinburgh. Again, the instructions for doing this are on our website. And this is important as there's a study going on there at the moment and it has been ongoing for many years, kind of collecting data on all the different reasons for death of red squirrels and other small mammals and this is really important for the work that we're doing, this research that's taking place. And it will also help us to ascertain if a red squirrel has died of squirrelpox and then for us to take appropriate action if that is the case.

And then if you've got a little bit more time on your hands, you can also volunteer with a project in one of our strategic areas, either with ourselves or with one of the local squirrel groups that's now set up in the south of Scotland. And there's also one in Fife in the Eastern lowlands as well.

So, there's various different opportunities within those groups or with ourselves joining our trap loan scheme, as I said earlier, helping with our strategic monitoring efforts to ascertain which species are in which areas. And the volunteer groups have lots of different roles. It doesn't necessarily need to be active. It can also be fundraising, helping with social media, all these things.

So, there's lots of different opportunities depending on what sort of thing you might be interested in. Lastly, we're always looking for people who are interested in getting involved with grey squirrel dispatch. This, in particular, is vital for helping us expand and increase our control efforts around the country.

So, if you live in one of our project areas and this is something that you're interested in doing, please do get in touch with your local conservation officer or with your Red Squirrel Volunteer Network, who will be able to offer advice and training on how to do this in line with our standard operating procedures in a way that is legal, safe and humane.

And it's important to say that our standard operating procedures are very strict and we do this in the most humane way possible. If you live outside one of our project areas, please do get in touch anyway and we'll be able to point you in the right direction for further information on this.


That's fantastic. Thanks so much, Katie. Hopefully everybody heads off to help out with those surveys or submit any sightings. Head over to



We're now joined by Professor Colin Galbraith who recently joined NatureScot as our new chair. So welcome and congratulations on your post.


Thank you very much. I'm delighted to be with you, both in the organisation and today.


Brilliant. Can you just tell us a little bit about your previous work, particularly regarding climate change and biodiversity loss and your involvement with invasive non-native species in particular please?


Yeah, I was previously a chair of JNCC, the Joint Nature Conservation Committee, which is the UK and the international bit, if you like, of what we do to an extent. I'm involved in the United Nations as well. And that work has taken me to really look at the impact of climate change around the world and then to look at that alongside other pressures on the environment and invasive non-native species are a key part of that pressure.

When you look globally, they are causing a huge amount of ecological change, a huge amount of damage to the environment and studying that at the global level gives a context if you like to what we're doing here in Scotland.


Colin, we've heard from Katie about all the important work being done in saving Scotland's red squirrels to ensure the long-term survival of that species. For all of these invasive non-native species being a top driver, as you say, for global, global biodiversity loss, can you explain to us why that is and, and how it's impacting that huge crisis?


I should say at the outset, I think what we heard from Katie is a really brilliant example of action that can be taken. So, there is action that we can take here in Scotland that we can take in other countries around the world.

So, really well done to the project and NatureScot are delighted to be part of that and supporting that work. When you look at invasive non-native species around the world, it is that surprise element. They appear very rapidly. They appear into a very rapidly changing climate as well. And they can probably do things they couldn't do 20, 30, 40 years ago because of that changing climate.

So, when you look at Britain in particular, we've got over 3,000 non-native species, would you believe, in wider GB of which most are established in the wild or naturalized, so they've come in and they've settled. Now, most of these are pretty harmless, they don't really cause huge problems. But a small number, somewhere around 10% maybe, have a real negative impact and that may be plant, it may be an insect, it may be other species. So, we reckon overall that we get about 10 or 12 new species into Britain each year and maybe one or two of these will then go on to cause a problem and there have been huge economic problems with them. We could maybe touch on that later. But it is a key issue.

You know if you think even very locally, giant hogweed, mink, Japanese knotweed, these are species that have come into Scotland, they are now part of our environment, but they really shouldn't be. And I think it's now a matter of taking the action that we can to eradicate them.


Yeah, and I think more and more people are beginning to learn more about these invasive non-native species and the kind of negative effects and even beginning to identify them and report sightings, which is again a really important thing to do. But, you know, we hear every day the nature and climate crisis is worsening, you know, it's on the media every single day.

How is climate change affecting the invasive non-native species that we have here?


Yeah, a lot of my work previously has been looking at the impact of climate change globally. What we're seeing now really in terms of climate change is really beginning to happen. We can see the climate in Scotland, in Britain, in wider Europe really changing and it's changing in a dramatic and at some points catastrophic way.

So, you have a situation where non-native species are coming into an environment that they may find quite amenable. They may be able to survive better because it's warmer or wetter or a combination of warm weather.

So, they can probably survive in parts of Scotland that they couldn't have done years ago. And I think because of that, we've got to look at our response. So, what does that actually mean? What are the problems? Well, we could see increased predation rates, increased disease transmission, and the grey and red squirrel is a good example, if I can call it that, of disease transmission, as well as straight ecological competition.

So, looking at that sort of competition is a real issue as well as the disease transmission. But Katie touched on it, you know, this is not a theoretical thing for nature lovers only, this is a hard economic argument here that if we have around £499 million impact per year in Scotland, that's a huge impact on our economy and that economy spreads across agriculture, forestry, tourism, our overall wellbeing, our overall experience of the countryside.

So, it's not just theory. This is hard economic practice that we've got to address these issues going forward. So, you know, we've probably all seen giant hogweed, for example, you know, the really tall plant, but the sap that it has, it can really cause skin irritation.

So, it's things like we need to avoid areas where there are giant hogweeds. We need to eradicate giant hogweed, mainly from the long river edges.

So huge economic cost in getting rid of the invasive species. The sensible thing to do is to try and avoid them coming here in the first place, of course.


Can you let us know what NatureScot and our other partner organisations are doing to, by way of dealing with these invasive and non-native species?


Yeah, and keep in mind my newness, as it were, in terms of new chair, but I'm learning very rapidly what NatureScot is doing, and it is hugely impressive, I have to say.

There are three categories of things that we are doing and can help others do as well. Firstly, it's prevention. Prevent new species arriving in Scotland. Look at our biological sort of security, as it were, in terms of what we're doing. Try not to import huge amounts of material that may have alien species on it. So, prevention is the first thing.

Secondly is early detection and monitoring. And I think that early detection, if we can catch species coming in very early and take action to prevent their spread, that's much more economically sensible than waiting 10 years or 20 years until they're established and then doing it. But actually, monitoring is really important. Where are the non-native species? What can be done? And again, I come back to the example that we had in terms of red and grey squirrel. If you had told me 10 or 15 years ago that we would manage to eradicate grey squirrels from Aberdeen, for example, that's a fantastic achievement. That really shows what can be done.

The third area that we're working in is management and control. And I think that management and control, it needs public support, it needs support from a range of landowners, a range of organisations, but we have that. And when you look at other countries around the world, other countries are taking action. One great example I know quite well is New Zealand, where they have large scale eradication programmes for non-native species. It would be great if Scotland could be working in the same way at that scale to get rid of non-native invasive species.


One important point to make is it's not just NatureScot and our partner organisations that have to or are dealing with these species. It's everybody, the general public, anybody can actually help in some way or another, whether it's reporting sightings of plants or speaking to children about these kinds of things.

It's really important to get the messages out there and our listeners are always keen to know practical things that they can do to help combat nature loss. So, what do you think your top ways are to make space for nature, particularly to do with invasive non-native species?


Yeah, I think that's the key point. You know, we're in the midst now of a nature and climate crisis, an intertwined crisis, and then you put invasive non-native species into that mix as well. It's a real cocktail of really hard ecological issues that we've got to tackle.

We can only tackle that if the general public get involved. We can only really be successful, again, if a range of landowners, managers, organisations, but the general public in particular get involved. And I think there are probably three ways they can do it. First of all, it's to volunteer to take part in citizen science projects like the project that we had, the Scottish Invasive Species Initiative to help control invasive species.

Secondly, take part in surveys. You know, the great Scottish Squirrel Survey that we had about in early October, a really easy and great way to contribute. Your data is really vital when you contribute to that kind of study. And then if you are lucky enough to have any even small area of land that you manage, and it may be from a window box right through to a large area of Scotland, it's look at what you're doing there in terms of the plants that you're putting in. Native species are better than non-Natives. You can help squirrels, you can help a range of nature across the country in very simple ways.

So, you know, take part, look at what you're doing, look at how you can help. And really encouraged by what I've seen so far in this project and in other projects. So, the key message is we can do this, you know, it's not a council of despair, it's a big task but we can all work together on it.


Thank you so much for joining us today, Colin and Katie. So, we've heard all about the invasive non-native species or INNS for those who enjoy an acronym. This problem is not going to disappear overnight. So please, we encourage you all to report sightings, volunteer where possible. And let's see what we can all do collectively to make sure we look after Scotland's native wildlife.


Thanks for listening. If you're enjoying 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

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