CONTENT WARNING: Will contain an image of a diseased squirrel some may find disturbing.
The UK is an island very familiar with invaders competing with, or integrating with, what already exists here and finding a way of making a new way of life.
Much to the chagrin of the ‘Jam and Jerusalem’ types who want to believe in an ‘English’ or ‘British’ identity, we are a nation of mongrels of various migrations and invasions for probably close to a million years. We have found fossils of pre-human Homo species, Homo antecessor, H. heidelbergensis and H. neanderthalensis dating back hundreds of thousands of years. We’re pre-historic mongrels.
Never mind the arrival of the first humans to these shores, whether those people became the historic Celtic group or if they, too, arrived from elsewhere, interchange with Gauls, invasions by Romans, Anglo-Saxons and the Germanic tribes, Vikings, Normans, Danes, all the way through to the opposite – our invasion of much of the rest of the world. Colonisation, and the import of different people and cultures, either specifically brought to Britain to be exploited, or else moving voluntarily to exploit opportunities presented here. Those who don’t believe in a multi-cultural Britain are wilfully ignorant of history. It is.
There is nothing new under the sun, they say, and there is nothing in Britain that hasn’t been somewhere else before.
Enter the Eastern gray squirrel (Sciurus carolinensis, being British I shall call it the ‘grey squirrel’) a clever, competitive and adaptable rodent, as many rodents are wont to be. The IUCN lists it as ‘least concern’ but many other wildlife and forestry groups in the UK disagree! Not because the grey squirrel is endangered, but because it, itself, is a danger.
The Eurasian red squirrel (Sciurus vulgaris) was, until around 1870s-1890s, our predominant, native species here in Britain. At that point, whether as exotic pets, nesting in imported trees or just because human beings are idiots, the grey squirrel was imported from North America. Most likely they were imported as pets because they were cute. I only give alternative options to make people feel less stupid. Released into the wild they seemed to spread quickly and showed themselves adept at outcompeting out native reds, for reasons we will discuss later.
Squirrels, as a family, are rodents (order Rodentia) in the family Sciuridae, the sciurids. They are a fairly disperse group, indigenous to much of the world excluding Australia (where they were introduced, but marsupials evolved by convergent evolution to fill much the name niche) and Antarctica (the ever-exception). The first squirrels date to roughly 50-30 million years ago (the Eocene).
We might associate squirrels with bushy-tailed tree dwellers, like the red and grey we will talk about today, or chipmunks (also a squirrel species). But there are also ground squirrels like marmots, groundhogs and prairie dogs, all scuiridae species.
Of those that do have a tail we find it is not merely an aid to leaping (as a sort of parachute) and balance (as with most tails on tree-dwelling or climbing animals) but can also be used for communication, as a heat regulation aid and also, quite adorably, as a little blanket to keep warm and protected.
I’m going to step in and do my mandatory people-bashing here, before I move on to the potential harms the grey squirrel causes.
They were initially transplanted from their native environment by people. A study of DNA analysis by Dr. Lisa Signorile reveals that, far from spreading across the UK in a wave of successful invasion, their distribution around Britain itself owes much to human intervention. People who had them as pets or populations in their gardens spread them to others. The population in Regent’s Park, as well as many other places, for example, can trace their lineage back to the 11th Duke of Bedford who gifted many of them from his Woburn Park home.
That estate now houses Woburn Safari Park. The 11th Duke, Herbrand Russell, was a keen animal enthusiast but not so good at understanding the potential impacts of non-native species becoming invasive. I would say ‘he can fuck off’ but our knowledge of wildlife and invasive species was nowhere near sufficient at the time for me to think the Duke anything more than a sentimental idiot with a penchant for cute animals and a passion for sharing them. He doesn’t get a free pass – but a stern telling off, education in how non-native species can impact their ecosystems and how he should be responsible when keeping them in the future and we’ll let him on his way!
One of the species keeping their populations naturally managed in Scotland and much of Ireland is the pine marten (Martes martes), a mustelid, in the same family as weasels and stoats etc. however the marten is much more arboreal than many of its related species, it hunts in the trees. Squirrels, both red and grey, are prey items for the pine marten. However, the red squirrel evolved with the marten, so they have an understanding of how to avoid predation. The grey squirrels seem to have none of this knowledge and the presence of a marten can lead to grey squirrels leaving a particular habitat.
Of course numbers of pine marten are lacking in England and Wales because, like so many amazing, successful native predators – we killed them! Funnily enough in the 19th century! Just when the grey squirrels were kicking off!
Most marten were hunted in retaliation for perceived livestock attacks, for their fur or, surprisingly often, for sport. Combined with the reduction of their preferred woodland habitat at the time, with increased industrialisation and the necessity of having more intensive farms to feed an increasing, and increasingly urban, population, it was curtains for the marten in England and Wales.
There is evidence the marten is moving further south from their Scottish outpost, with likely populations in Northumberland and Yorkshire, some in Wales. However the once abundant woodlands, their habitat, are now absent. With no wildlife corridors to allow the marten to migrate south easily their spread will be slow, or completely halted, without human-assisted reintroductions. A wider spread of pine martens could improve the situation with regards to the grey squirrel in our woodlands but the grey squirrel is adaptable to our urban and suburban environments and trials seem to suggest the marten has little success hunting them there. Ousting them from our urban centres is going to be difficult, and the question may need to be asked “Should we?”
So the Eastern gray squirrel, or grey squirrel as we call it over here is an invasive species originally from North America, specifically the Eastern side, which can probably be determined by its name. They are also mostly grey, although some can have browner, tawny, or even reddish patches of fur, and melanistic (black) individuals are known to exist. They aren’t huge, around 20-30cm in body length with a slightly shorter tail – so up to 60cm from nose-to-tail. Their bushy tail is a pretty obvious sign of a squirrel.
An interesting piece of physiological information is that they have much freer-jointed feet, allowing them to turn them completely 180°! If you wondered why grey squirrels seem just as comfortable running up and down trees, this is why – by reversing the angle of their ankles they can effectively change the direction of their claws’ grip and not have to worry about slipping. It’s an exceptional adaptation that allows them that signature speed and agility going up and down tree trunks.
Ethologically (animal behaviour) speaking you might consider the squirrel quite a dumb creature. If you’ve ever had one trapped in your house and you’ve tried to usher it out you will likely be sure they’re stupid. If you’ve ever seen one try to solve a puzzle or maze to get some food you would almost definitely disagree. If, like some people, you have observed them exhibiting deceptive, trick behaviour, you might be inclined to suggest they have some consideration of others and their motivations, otherwise known as ‘theory of mind’.
Let me explain.
Grey squirrels, and many squirrels, in fact, are what’s known as scatter-hoarders. They don’t just eat the food they find, they bury caches of it so that they have something for leaner months. Squirrels do not truly hibernate, so they may require food during a particularly harsh winter or if they fatten up sufficiently beforehand they are looking for a nice meal when spring arrives. So they will find a food source, eat a little, gather a lot, store it – sometimes even temporarily, in caches they will move to a main, more secure one, later – and then when the time comes they use memory and smell to uncover their caches. It is estimated a squirrel can bury several thousand nuts and seeds in a season, creating thousands of caches. They are nothing if not industriously hungry.
However, cache thievery is also a thing. Not only from other squirrels but other species too. So the grey squirrel has been seen exhibiting false caching behaviour. If they feel they are being watched they will mimic burying food, digging, placing the food, covering the cache etc. all whilst concealing the food in their mouth.
They will also adapt these behaviours. Sometimes they will conceal themselves behind leaves, if they feel they are being watched by a terrestrial (ground based) thief they will hide their food in trees.
It is this adaptation, this complex repertoire of behaviours that could potentially suggest a theory-of-mind level intelligence in squirrels. They are aware of the other animal’s intention (i.e. to steal their food) and they adapt their own behaviour based upon their prediction of what the other animal is thinking.
So squirrels are not stupid. I would argue few, if any, rodents are ‘stupid’. They are widespread, numerous in species, diverse and populous for a reason!
One thing people ask me about squirrels is their babies. Have you ever seen a baby squirrel? Unless you’ve been unfortunate enough to see a fallen nest, or ‘drey’ as they are known, or work with squirrels, no you probably haven’t. They build their dreys up in trees, and they look like a nearly spherical bundle of sticks, often lined with softer straw, grasses or feathers.
Grey squirrels are believed to be polygynous so multiple males will mate with a single female. They tend to have one or two breeding seasons a year, one of which often coincides with over-wintering so, one of the main reasons you don’t see many baby squirrels is a lot of them will be born during the winter months and won’t emerge until spring. There can also be another breeding season in mid-summer.
This should give you another good idea of why you don’t see a lot of baby squirrels. Like many rodents they go for quantity over quality. It started as a concept in ecology known as the ‘r/K selection theory’ and it’s the idea that a reproductive and parental strategy depends on how cheap or expensive it is to make more offspring. Nowadays we use ‘Life History Theory’ but it still incorporates a lot of the aspects of the r/K theory – effectively a cost-benefit analysis of whether or not to give a shit about your babies.
Rodents tend to be breeders. It is cheap for them to breed so they pump ‘em out, give them as much care as they need to not die too much and send them on their way. Other organisms like whales, for example, diffeer. The development of a gamete, a sex cell, a sperm or an egg, is already a huge energy investment. Never mind the mating, the fertilisation, the ovulation, the birth, the feeding – it takes a huge amount of investment to turn one, say, blue whale gamete into an adult blue whale. So they invest a lot more in a smaller number of offspring.
Well, as I said, squirrels shag a lot and pile ‘em high. A baby squirrel goes from being a blind and toothless severed thumb looking thing to a small squirrel in about 10 weeks. Two and a half months! This is why you don’t see them. Or rather, you do! It’s just by the time they leave the drey they just look like slightly smaller squirrels. Squirrels do not display a huge amount of sexual dimorphism (bodily difference between sexes) either. So if you’ve ever wondered why you don’t see boy squirrels and girl squirrels, you do! You just can’t tell them apart!
It should go without saying they are mostly vegetarian and eat a lot of nuts and seeds. With gnashers like theirs you pretty much have to, as far as I know all rodents have to gnaw their incisors, their ever-growing front teeth, down. If they don’t they grow and protrude through the lips and the jaw causing great pain and distress. Besides nuts and seeds greys will eat flowers, berries, some mushrooms (I now want to see a squirrel tripping) , they chew bark on trees (in fact this is one of the leading environmental damages they cause as an invasive species in the UK besides outcompeting the red squirrel) and they will raid gardens for a bit of fruit and veg. Grey squirrels have also been observed eating insects, other small rodents, and particularly bird eggs, another area of potential ecological damage.
Let’s move on to the red squirrel then, before discussing ‘the issue’ because I personally think this is much more complex than ‘grey squirrel bad, red squirrel good’.
We perceive the red squirrel as being an ‘endangered species’ here in the UK because to us it is. Globally, though, it’s doing just fine and the IUCN has it of least concern. It is widespread pretty much from one end of the Eurasian continent to the other, from Britain and Portugal in the West over to the Pacific coast of Russia in the East. It spreads down into south-east Asia a bit, isn’t quite in south-west Iberia and there’s some concern about a population of greys ousting them in Italy, but otherwise it’s pretty comfy.
Even in the UK the Scottish population is fairly set, understanding of the relationship with pine martens, as well as management of grey squirrel populations (any time I use the words ‘management’ or ‘control’ with regards to an invasive or overly abundant species just read it as ‘killing’, that’s usually what it means) has meant it is fairly stable there. There are also populations in Ireland, the Isle of Wight and in a few isolated spots in the North of England, I believe Formby has (or had) a decent population and they were not unknown in the North East.
They’re a little smaller than their grey cousins, only 18-25cm in body, 15-20cm tail and a couple hundred grams lighter around 250-300g. Again there is little to no sexual dimorphism, so it will be difficult to tell females and males apart by sight. They can obviously be told apart from the grey squirrel by their red coat but in winter they tend to get a touch of grey mottled fur (agouti, I think the coat pattern is known as – not to be confused with the rodent of the same name!) so one sure-fire way to spot-the-difference is to check the ears. Greys have little, round ears with no discernable floof, reds have long tufts of hair on their ears. Just like greys they are also subject to colour morphs and brown or black specimens appear common, especially around the alpine regions. I myself have seen a black red squirrel in Switzerland.
A study on melanistic grey squirrels found that there was a thermal benefit to that colouration so perhaps it is an adaptation particularly common in the cold, mountainous regions due to this thermal regulation and the benefits it give in terms of metabolism and cold resistance.
From there, if you can believe it, most of the information is the same as with the greys. They forage the same, eat the same, behave in a very similar way and as far as we can tell do not directly compete with one another so, you might be wondering, how did we see such a crazy decline in our red squirrel numbers in the UK?
I will move on to what I think the major contributing factor was last but let’s talk about some other stuff first.
Squirrel parapoxvirus – Effectively squirrelpox! (before you ask whilst many pox viruses are zoonotic – able to be transmitted from animals to humans – there have been no recorded cases of human squirrelpox, so don’t worry!) It is a disease common in squirrels. The grey squirrels can have it pretty much symptomless, they seem quite immune, but they act as carriers and spread it to red squirrels, where it can be deadly.
It causes ulcers and lesions on the skin, particularly around delicate areas (eyes, feet, genitals etc.), and causes lethargy which naturally impacts foraging or predator escape behaviours. What is more, studies on red squirrels for antibodies have found that individuals with historic antibodies for the virus can still die of later cases of it. This suggests that either the antibodies do not bestow full, permanent immunity to the virus or the virus is capable of adapting and evolving to re-infect the host. Either way it makes it a pretty effective tool for killing off red squirrels.
You know how oak trees are pretty common in the UK? Being an entire ecosystem unto themselves, especially if they are a large oak? Well red squirrels digest acorns less efficiently than the greys. Given the number of UK oaks, as well as the number of acorns a single oak can produce this is a huge boon to the grey squirrel and another reason they have outcompeted the red squirrel.
It has also been suggested that when subject to stress the red squirrel has trouble in the bedroom! That’s gonna affect the population!
But! What I want to talk about is two-fold and I think possibly the most important thing to consider. One – Loss of forest and the composition of new-growth forest in the UK. Two – The relative abilities of the red and grey squirrel to adapt to an urban or suburban environment.
I’ve already partially mentioned one issue when discussing the pine marten and that’s loss of woodland and habitat fragmentation.
According to the British Ecological Society in 2008, in the prior decade, a 100 square mile area of woodland had been lost to, mostly, human development.
Since then there has been a big effort to restore woodland but ‘with what?’ is a very pertinent question to ask. Ancient British woodland is a very diverse mixture of conifers and broadleaf trees, many of which face their own problems. If we are attempting to plant mono-culture (single species) forests these may not necessarily support the biodiversity required of ‘healthy’ British woodland which red squirrels might be better adapted to.
Then there is the fragmentation issue. It doesn’t matter how much extra cover we have if it is all in a few square miles here and there with nothing to connect it, with no continuity or corridors through which wildlife can migrate and disperse.
Projects like the entirely unnecessary HS2 train line, these white-elephant transport projects that are doing little to solve the main problems of the transport networks, are having a huge impact on two things – The state of our natural environments and the fatness of the pockets of the lawyers, the consultants, the accountants, the advisors and the developers on those projects. There is a clear focus on profit and greed above maintaining a healthy, stable set of UK native ecosystems and habitats.
It is my opinion that every development needs to be a ‘nature first’ development. This, to me, means we should find a way to keep the old, or build a new, biodiverse ecosystem around the developed area and design any development accordingly. However the stumbling block is this is expensive and that’s what this comes down to. In the short term it is always cheaper to level the natural world and build up an airport expansion, a new bypass or some houses. Unfortunately the knock-on effects of having ‘paved paradise and put up a parking lot’ are always significantly more expensive in the long-term and if we do not start thinking long term now…Well there just won’t be a long term to think about!
Without due care and attention to the environment the long term is every man, woman and child being thrust into a crisis of our own design and killing each other for basic resources like water! Yes, it might prove costly now, but our future will see a lot less conflict and a lot more prosperity if we start investing in our environment and our native species, their habitats and ecosystems now, before it is too late.
Never mind the red squirrel. Having the consideration to create a network of diverse, interconnected woodlands is having a consideration of the environmental stability of our future. We don’t have that at the moment.
So red squirrels will never thrive without those woodlands but what about getting rid of the greys?
In my opinion, without doing serious damage to the wider urban and suburban ecosystems, it’s nearly impossible. Unlike the red, the grey squirrel seems much more adapted to sparse tree cover and access to parks and gardens like we have in our urban and suburban environments. I didn’t even see a red squirrel walking through several woodlands in Scotland. I can see a grey squirrel walking up my local park in an area that has about 6 trees!
We could revitalise our woodlands, reintroduce pine marten to them, use the marten and some control measures to reduce or eradicate grey squirrels from the woodland, reintroduce red squirrels and they’d do great in the woodlands.
But pine marten don’t work so well in urban environments, and nor do red squirrels. A study in Finland did find red squirrels capable of urban exploration, but in Finland there is no problem of grey squirrels! The discussion seemed to be that so long as there were sufficient trees around red squirrels would live in an urban environment but grey squirrels positively thrive in them, even with minimal tree cover.
Potentially the only way of encouraging urban red squirrels is through complete eradication of the grey squirrel population from urban and suburban environments and, again, how would one propose to do that without a major disruption of the urban and suburban ecosystems? Some kind of poisoning is likely going to be the only effective way and that would surely have a knock-on effect with predators of squirrels. Manual hunting will be like cutting off the heads of the hydra. In a species that can have up to 8 young in a litter, although 4 is more normal, of which, on average, 2 survive, but they do so twice a year. It will be an uphill struggle and one we have to ask whether it is worth it!
I think a heavy focus on forest cover, increase of pine marten in those forests and reintroduction of red squirrel populations into those forests is a good place to start. With the martens and forest wardens keeping an eye out for greys. We make our woodlands a protected fortress for red squirrels.
As for the grey squirrel, they can remain in our towns, our cities, our urbs and suburbs. They may be an unwelcome guest at the party, and they may get a little rowdy and cause some trouble, but everyone seems to love them. Let them remain, with the buddleia (incidentally also introduced in around the 1890s), the muntjac deer (Incidentally also spread from Woburn Park!) and the ring-necked parakeet as examples of how seemingly innocuous and charming imports can thrive on our island.
Let them be a beacon of warning, that never again should we import species without due care or understanding of how they might thrive and spread here. Let them be the symbol never to make the same mistake again.Follow @wldiscipline