In Britain we have our native Red Squirrel and the introduced Grey Squirrel. More recently Black Squirrels, which are a colour variant of the grey squirrel, have been observed in several southern counties of the UK.
Since the introduction of the grey squirrel in the 19th century, the red has suffered serious declines and is now only found in small pockets of the UK, with the majority being in Scotland. By contrast the red squirrel is widespread in mainland Europe. Contributing factors to the decline of the red here in the UK includes the fact that grey squirrels carry the squirrel pox virus to which red squirrels have no immunity. Grey squirrels are also larger and more adaptable and out-compete the reds for food and territory. In recent years there have been calls to control the population of greys, particularly at boundary areas where reds are being pushed back. The problem is that if you trap grey squirrels then it is illegal to release them back into the wild in another location as they are classified as vermin. Therefore once trapped the only legal option is to shoot the grey squirrel.
Grey squirrel (Sciurus carolinensis)
The grey squirrel is well known to us as it is widespread throughout British gardens and parks. Some consider it to be an athletic and entertaining little creature, but it can certainly be a great nuisance in the garden, particularly if you are a bird lover. The grey squirrel is very bold and soon learns to take food from bird tables and destroy bird feeders.
Distribution: Native to North America. Introduced species in Great Britain, Ireland & South Africa
Habitat: Prefers mature deciduous woodland but also common in parks and gardens in towns and cities.
Description: Winter fur is dense and silvery grey with a brown tinge along the middle of the back. Summer fur is yellowish-brown. White underparts. Bushy, grey tail. Ears without tufts.
Size: Head and body about 25 – 30cm; tail about 20 – 25cm. Weight: 350-600g.
Life-span: Some live up to 10 years in the wild although most only manage 3-4 years.
Food: Hazelnuts, acorns, beech mast, tree bark, fungi, buds, leaves, shoots, flowers; will also raid birds’ nests for eggs and young.
Population: The grey squirrel was first introduced to Great Britain as a fashionable addition to country estates and parks such as Woburn in Bedfordshire. After many releases/escapes the grey population began to increase dramatically at the beginning of this century. Today the Grey Squirrel is one of Britain’s most well-known and frequently seen mammals, with an estimated population of 2.5 million in the UK.
Daily life of a grey squirrel
The grey squirrel is diurnal and most active at dawn and dusk, searching for available food. Compared with the red squirrel, it spends more time foraging and feeding on the ground than in the trees. It is also very agile in the trees and can run along slender twigs, leaping from tree to tree. The long, muscular hind legs and short front legs help it to leap. The hind feet, longer than the front, are double-jointed to help the squirrel scramble head first up and down the tree trunk. Sharp claws are useful for gripping bark and the tail helps the squirrel to balance. If a squirrel should fall, it can land safely from heights of about 9m (30ft). The grey squirrel can leap more than 6 metres!
Squirrels have good eyesight and often sit upright on a vantage point to look around them. They have a keen sense of smell too!
The grey squirrel builds itself a nest, or drey, about the size of a football, made of twigs, often with the leaves still attached. It is built fairly high in a tree and lined with dry grass, shredded bark, moss and feathers. A summer drey is usually quite flimsy and lodged among small branches. Sometimes the squirrel may make its nest in a hollow trunk or take over a rook’s nest, constructing a roof for it. A squirrel may build several dreys.
Grey squirrels have a wide range of calls including territorial barks or even ‘quacking’ noises. However, they mainly communicate through their tails, using them as a signalling device; they twitch their tails if they are uneasy or suspicious. Regular routes are scent-marked with urine and glandular secretions. Squirrels identify each other, and food, by smell.
During Winter the grey squirrel does not hibernate as it cannot store enough energy to survive for long periods without food. To survive the lean cold months of Winter a larger, thicker winter drey is built, usually on a strong branch close to the trunk. The squirrel will lie up in the drey in very cold weather, coming out now and then to search out hidden stores of nuts buried in the ground in autumn. The stored nuts are spread around rather than in a single cache and are found by smell, rather than memory. Often they are not found at all and later may grow, helping the dispersal of trees. Winter dreys are often shared for warmth. As it sleeps, the squirrel curls its tail around its body to act as a blanket.
In late winter, squirrels may be seen courting, one, or more, chattering males chasing a female through the tree or across the ground. Females can mate only twice a year, but males may mate at any time. After mating, the male plays no part in the rearing of his young.
The female uses a winter drey as a maternity nest, or builds a new one. She lines it with soft material and gives birth after a six week gestation period (time between mating and birth), in March/April and perhaps again in June/July.
An average litter has 3 babies but as many as 9 may be born. The mother suckles the naked, blind young every three or four hours for several weeks. They gradually grow fur, their eyes open and at about seven weeks old they follow their mother out on to the branches. Gradually they start to eat solid food and when their teeth are fully grown, at 10 weeks, they give up suckling. A month or so later they move away from the nest to build dreys of their own. If there are not too many squirrels in the area, the young stay nearby; if it is crowded they will be chased away to look for less crowded feeding areas.
Grey squirrels breed for the first time at a year old.
Grey Squirrels and threats to UK Wildlife
Since their intentional release into the countryside, grey squirrels have spread and flourished and we are now trying to control their numbers. The invasive grey squirrel pose threats to native red squirrels, trees and many of our woodland birds.
Foresters, gamekeepers, park keepers and many conservationists regard grey squirrels as pests, mainly because they damage trees. Young saplings (sometimes rare species) are destroyed and they gnaw the bark of hardwood trees, such as beech and sycamore, to get at the nutritious sapwood below. The raw scar left on the trunk encourages fungal attack and may lead to distorted growth.
There is growing evidence that grey squirrels are affecting native woodland bird populations in three ways. Firstly by eating eggs and baby birds from the open nests of birds such as thrushes and finches and discouraging birds from using nest boxes. Secondly, squirrels use ideal nesting spots that would usually be occupied by birds such as the tawny owl, kestrel, jackdaw, stock dove and starling. In some areas it has been reported that squirrels can halt the breeding of tawny owls altogether by taking up these useful nesting sites. Thirdly, they eat the same food. Squirrels have been seen taking a bird’s store of winter foods and their diet means that they are in direct competition with other birds such as the nuthatch, hawfinch and bullfinch.
In many forest areas, the grey squirrel population is controlled by trapping and shooting. Gamekeepers shoot the squirrels on private estates. It is illegal to keep, import and release grey squirrels in Britain, unless you have a special licence from the Ministry of Agriculture or Secretary of State for Scotland. The Forestry Commission and National Trust also trap and shoot grey squirrels and sometimes they put them on the menu! Squirrels were eaten a lot in the past and now they are coming back on the menu in some places including London’s top restaurants.
The Black Squirrel is the same species as the grey, but with a mutation of the gene that controls coat pigmentation – giving rise to their black colouring. The black squirrel was first recorded in the UK in 1912, but is restricted to the counties of Bedfordshire, Hertfordshire and Cambridge. This strongly suggests that all the UK black squirrels are descents of the original black squirrels imported from the USA to one private menagerie in the area at the turn of the century. As they are the same species, the grey squirrels and black squirrels can interbreed and produce melanistic offspring with the black colouration carried in the dominant gene. The dark colouring is generally known as Melanism from the Greek meaning ‘Black Pigment’. Melanism occurs in other species such a Black Panthers and Jaguars and tends to be an adaptive response enabling better camouflage and survival in the environment.
Red Squirrel (Sciurus vulgaris)
The Red Squirrel is the original ‘Squirrel Nutkin’ of Beatrix Potter fame and was widespread in the UK until the 1940’s. Since this time they have suffered sharp decline in numbers, now being classified as an endangered species. This decline is directly linked to the rise of the grey squirrel population.
Distribution: Scotland, Wales, Ireland: a few habitats in England – Isle of Wight, Brownsea Island in Poole Harbour, Thetford Forest in Norfolk. Widespread in rest of Europe.
Habitat: Coniferous forests of Scotland and Wales; mixed woodland in England and Ireland.
Description: bushy tail; ear tufts; coat colour in adults can vary from cream, through all shades of red and brown to black. Ear tufts and tail may bleach to cream in summer.
Size: head and body up to 24 cm, tail up to 20 cm, weight up to 350 g.
Life-span: about 3 years, but up to 7 years possible.
Food: seeds of a wide variety of trees, buds, shoots, flowers, berries, nuts, bark and fungi.
Population: 120,000 in Scotland, 3000 in Wales and 15,000 in England
Red Squirrel Behaviour
Territory: the favourite habitat of the red squirrel is a large, mature Scots pine wood but they will also live in deciduous woodlands. The squirrels live mostly high up in the trees and build nests, dreys, in the forks of branches. Often two or three dreys are in use at any one time; these may be close together or wide apart, depending on the squirrels’ range. Males may live in an area of up to 17 hectares (the size of 34 football pitches). In the winter and early spring squirrels of all ages and both males and females may share dreys but only if their territories overlap and they feed close together i.e. they know each other. Drey sharing usually stops in late spring and summer when the females are raising their young.
Daily Life: red squirrels are diurnal and are active for much of the day, often from before dawn until it is dark, pausing only for a midday rest. They have few natural predators so can take the risk of being out in broad daylight. They escape attack from foxes and birds of prey by spending most of their time up in the trees. They forage on the ground for brief spells, particularly in autumn when they collect acorns, beech masts and other nuts to store for winter.
Squirrels hold food in their forepaws. A favourite food is pine cones; they bite the scales off the cones to get at the seeds. The ground under a pine tree may be littered with chewed cones and scales.
When squirrels are not feeding or resting, they are scratching (they are usually covered in fleas!) and washing.
Winter: during the autumn red squirrels eat as much as they can to put on fat reserves for winter. They put on about 12 per cent of their body weight in autumn fat whereas a grey squirrel can put on as much as 25 per cent.
Breeding: the mating season often starts on warm days in January, the squirrels chasing each other through the branches. The female red squirrel may produce two litters in a good year, one in the spring (April) and the other in summer (August). There are, on average, three babies in a litter. The breeding drey is usually a little larger than normal with a thick, soft, grassy lining. The young are born blind and naked. If she is disturbed, she will carry the babies in her mouth, one by one, to another nest, which is sometimes quite a distance away.
As the young develop, the female spends more and more time away from the drey, and by the time they are three weeks old she may leave them for several hours at a time. The male takes no part in rearing the young.
At seven weeks the young begin to venture away from the nest and at eight to ten weeks they are weaned and become independent. Their fluffy, darker baby coats change into the adult colour.
The success of the breeding season i.e. the numbers of babies born and raised, depends on the seed crop of the main trees where they live. Where there are plenty of acorns, pine cones etc. squirrels build up a lot of body fat and many survive the winter in good condition. This means they will start breeding early in the next year and rear many babies. In a year when there is a shortage of tree seeds, the squirrels do not put on much fat and they may die from starvation or disease during the winter. Most of the survivors are not fit enough to breed successfully.
Protecting the Red Squirrel
A lot more information about red squirrels will have to be gained through careful observation in the wild. In this way we may be able to decide exactly why they have declined so dramatically and work out ways in which we can help them recover. One way may be to provide extra food rations to help them over bad winters. Another way, as with the otter, may be to breed them in captivity and re-introduce some into protected, suitable habitats.
In January 2012 two new breeding enclosures for the red squirrel were opened in Norfolk. These two sites brings the number of breeding areas up to 10 in a bid to increase red squirrel populations. These controlled areas allow squirrels to be secluded from the threat of grey squirrels and other predators.
For more information visit the websites of the Red Squirrel Survival Trust and the UK Red Squirrel Group.