Drawing inspiration from the goings-on in his own back garden, Dr Terry Mabbett takes a sympathetic look at the grey squirrel as he considers the damage it does to Britain’s native trees.
THERE’S no dispute about the extent and level of damage to broadleaf trees caused by grey squirrels. Beech, sycamore, oak, poplar, sweet chestnut, birch, hornbeam and willow are among those most prone to attack and bark stripping, though the exotic rodent will gnaw and strip the bark off of almost any broadleaf tree.
Grey squirrels generally target trees between 10 and 40 years old. Very young trees or saplings (with a stem diameter of less than 5 cm) generally escape because they cannot support the weight of the squirrels. It’s a similar story with the main stems of older trees (40-plus years) because the bark is too hard for the squirrel to strip.
The grey squirrel’s target tree list covers a complete range of mainstream native and naturalised broadleaf species utilised in UK forestry, at a time when English elm and common ash, two of the traditional ‘top five’ hardwood timber trees, are already lost.
Grey squirrel continues to prevent universal planting of beech and sycamore. Sycamore is sometimes planted as a sacrificial crop to keep squirrels away from more favoured trees like English oak. The exotic but now naturalised sweet chestnut has potential pest and disease problems with chestnut blight, Phytophthora ramorum and oriental chestnut gall wasp, as well as having to contend with bark stripping by grey squirrels.
Other exotic tree species like Norway maple, having performed well in UK forest trials and with good timber credentials, have not been planted on large scales through fear of damage. Cricket-bat willow – recently in the news as a target species for the newly reintroduced native Eurasian beaver – can be severely damaged by grey squirrels. Landowners may avoid damage from beavers by planting cricket-bat willow away from the waterside or by installing wire mesh around the base of the tree. But these measures are of little use against grey squirrels operating over much wider areas and higher up in trees. Severely damaged hornbeam may avoid death because the fluted (folded) nature of the main stem prevents squirrels from completely ring-barking and killing trees.
Greys clearly cause a lot of economic damage, for which they are persecuted by landowners and foresters (and understandably so), but attitudes to the animals in towns and cities could not be more different.
Young children are given regular trips to parks, ostensibly to feed ducks, geese and swans, though these invariably end up as dual waterfowl–grey squirrel feeding exercises. My Australian grandchildren, no strangers to larger-than-life wildlife back home (including koalas, kangaroos, wallabies and some amazingly tame Australian native rodents), were captivated by grey squirrels in our local parks and spent hours feeding them everything from cream crackers to acorns.
Youngsters’ fascination with squirrels is cemented by countless storybooks such as Hazel Squirrel, read over and over again for my children some four decades ago. I can’t remember whether Hazel was red or grey and I doubt whether my children cared. However, irrespective of fur colour, they would have been mortified to learn that big hairy humans were blasting their furry friends.
Grey squirrels will eat the eggs and nestlings of garden birds, but, to be fair, so do native red squirrels. Most damage in gardens is to bird feeders, but this is easily avoided by erecting dedicated squirrel feeders at the same time. It costs a fortune in peanuts, but what the hell. With COVID-19 restrictions, I can’t travel to do articles on grey squirrels stripping bark from hornbeam coppice in rural Hertfordshire, so I might as well get some enjoyment watching them crunch and munch Arachis hypogea in my suburban garden. Besides, I might be giving a leg-up to groundnut growers in Africa.
Talking of dedicated squirrel feeders, a team of enterprising experts in animal behaviour at the University of Exeter has found ambidextrous squirrels are more brain efficient than those which favour the use of one paw or the other. Led by Dr Lisa Leaver, the research team designed an experiment in which 30 grey squirrels were presented with a Perspex tube containing peanuts. To access the nuts, greys had to learn to use a paw, rather than their mouth, because their faces were too big to fit through the holes of the tube.
Dr Leaver said: “We were measuring how long it took them to stop using their faces and to start using their paws to reach into the tube. And once they started doing that, we measured which paws they were using – left or right.”
While some squirrels showed ambidexterity by using both their paws to access the nuts, others strongly favour one side. The team then measured how quickly squirrels learned the task and how strongly they favoured a particular paw, assessing both learning and laterality. Results showed squirrels which strongly favoured a particular side did less well on a learning task. Or, in boffin jargon: “strong lateralisation is linked to poor cognitive performance”.
Findings were reported in the national press which predictably had a field day with headlines like ‘Southpaw sorrow for squirrels’, ‘Paws for thought – the secrets of a smarter squirrel’ and ‘Using their nuts … squirrels who use both paws out-think rivals’. Perhaps the ultimate was the caption for a national daily cartoon depicting a squirrel sitting down to dinner with a pensioner couple: “I don’t care if he is left-handed – he should be holding his knife with the right hand!”
Grey squirrels clearly cause extensive damage to trees, damaging parts of the landscape and the livelihoods of many who work them; and they continue to threaten the very existence of our native red squirrel. However, they also cause a lot of amusement and provide entertainment for millions who live in urban and suburban areas from where, to be fair, red squirrels had probably vacated before the grey squirrel was introduced in the 1870s. I never heard my grandparents, who would have been working the land in south Hertfordshire and north-east Middlesex by the 1880s (still very rural at that time) relay either directly to me or through my parents the presence of red squirrels in this area just north of London.
I searched the archives for red squirrels in Hertfordshire and the only reference found was a sad story about the last red squirrel at Hitchin in North Hertfordshire. Around 1910, an elderly lady called Miss Hailey rescued the animal from a group of youths who were tormenting it in a Hitchin churchyard. Miss Hailey lived at the Biggin Almshouses nearby, and fed the squirrel, which became semi-tame and apparently continued to live around the Biggin (originally a 14th-century priory), until the day she found it dead in the snow – probably the winter following its rescue. It was stuffed and mounted and later donated to the North Hertfordshire Museum.
Grey squirrels had apparently colonised Hitchin by 1910, so this little fellow may have been one of the last native red squirrels living in the town itself. Red squirrels apparently clung on in rural North Hertfordshire, with last recorded sightings being a pair three miles from Hitchin at Highdown Woods in 1943 and individuals seen in Knebworth Park and on Preston Hill, both in 1944.
Of interest in all of this are the views of scientists at Queens University Belfast investigating the potential role of pine martens for grey squirrel control. Lead researcher Joshua Twining says pine martens are driving grey squirrels away rather than killing and eating them in large numbers. Red squirrels’ ability to exist quite comfortably alongside a fellow native but nominally predatory species (the pine marten) appears to be down to innateness and instinct rather than learning. The last time pine martens and red squirrels existed alongside each other in numbers across large tracts of the UK was the first half of the 19th century, if not earlier.
According to Joshua Twining, the issue of grey squirrel control in highly (human-) populated areas needs addressing, lest we create a situation where pine marten-savvy grey squirrels re-colonise the wider landscape in future. However, that’s where politics and public perceptions may come into play.
Ruislip Woods, in the old county of Middlesex (now the London Borough of Hillingdon), the largest expanse of traditional oak standard over hornbeam coppice woodland, is a haven for grey squirrels to bark strip the hornbeam poles. From the 1960s to the 1980s, the Ruislip Woods complex was closed to the public, woodland by woodland, once per year for 14 days, to allow a highly organised team of guns to undertake grey squirrel control. During the 1980s, the council was politically split and, after endless debate, squirrel control was abandoned and has never resumed. Organised, countrywide grey squirrel control in urban areas has about the same probability for success as finding a single, sustainable vaccine for long-term protection against COVID-19.
AUTHOR’S NOTE
Grey squirrels may finally get their comeuppance, ironically from one of their own at Hitchin and the surrounding area, including neighbouring counties of Cambridgeshire and Bedfordshire. First reported in 1912, black squirrels are a melanin-containing subgroup of Sciurus carolinensis (North American eastern gray squirrel, the one currently causing collapse and confusion in UK forestry).
At one time, the black squirrel was thought to have arisen from a mutation occurring in the introduced grey squirrel population this side of the Atlantic Ocean. However, black squirrels are now said to be the result of long-established crossing between North American eastern gray squirrel and North American eastern fox squirrel (Sciurus niger). A single specimen is thought to have been introduced into the UK around the same time as the grey squirrel.
As the common name suggests, fox squirrels normally have red-brown fur, but there is a dominant mutant gene in the population which is expressed as black-furred individuals in the hybrid population. Be that as it may, black squirrels in Hitchin and surrounding areas are faster, fitter and more fiercely territorial and aggressive than their common-or-garden grey cousins.
And their sleek, black fur is claimed to be more attractive to female grey squirrels, which means black squirrels could eventually rule the roost across much of England.
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