Grey squirrel: Sciurus carolinensis
Distribution: Native to North America. Introduced to Great Britain, Ireland and 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 introduced to Great Britain in the mid-19th century and after many releases it began to increase dramatically at the beginning of this century, mainly spreading from Woburn Park, Bedfordshire. They came to England from North America and are now one of Britain's most well-known and frequently seen mammals, with an estimated population of 2 million. They are much more common than the native red squirrel who's population is estimated at just 140,000.
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, however, 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.
Although grey squirrels have a wide range of calls, they communicate mainly 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.
Winter: The grey squirrel does not hibernate and it cannot store enough energy to survive for long periods without food. A larger, thicker winter drey is built, usually on a strong branch close to the trunk, and a squirrel will lie up in this in very cold weather, coming out now and then to search out hidden stores of food. These stores of single nuts and other items are buried in the ground in autumn, well spread out. They 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 humans
Humans are the main predators of grey squirrels in Britain. Since intentionally releasing them into the countryside in the 19th Century they have spread and flourished and now we are trying to control their numbers. As an invasive species these squirrels, although cute and cuddly, are causing many problems to other animals, trees, birds and humans! The three greatest impacts of the grey squirrel to UK wildlife are to native red squirrels, trees, and many of our woodland birds.
Grey squirrels seem much stronger and more adaptable than our native red squirrels and have taken over many of its former territories. This is partly because grey squirrels carry the squirrelpox virus, to which they are immune, but which affects red squirrels. Also, their larger size makes them the obvious winners in any physical confrontation with red squirrels.
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 effecting native woodland bird populations. It is thought that these foreigners are affecting birds 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.
Although the grey squirrel is a pretty, appealing and entertaining little animal, it can be a great nuisance in a garden too, especially to a bird lover. It is very bold and soon learns to take food from bird tables and chew through baskets of peanuts. It will also destroy birds' nests to eat eggs and nestlings.
Red Squirrel: Sciurus vulgaris
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, hoots, flowers, berries, nuts, bark and fungi.
Population: 140,000, mostly in Scotland
The red squirrel, the original 'Squirrel Nutkin' of Beatrix Potter fame, is one of our favourite British mammals but it is declining in numbers and classified as an endangered species. The reason for its disappearance from most of its old deciduous woodland homes is largely down to the North American grey squirrel (population 2million) that carries the virus parapox, deadly to our native red squirrels. The slightly larger grey squirrel also directly competes with red squirrels for food and nesting sites.
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.
Red Squirrel Problems
Until the 1940s the red squirrel was quite widespread. It has now disappeared from large areas of Britain and its place has been taken by the grey squirrel. The larger grey squirrel was introduced to this country in the mid-19th century. Research has shown that grey squirrels put on a lot more body fat than red squirrels which gives them a better chance of surviving. The larger, more robust grey wins in the competition for food and space and it is now widespread in England and Wales. It is more adaptable than the red squirrel and lives happily in hedgerow trees, parks and gardens as well as large woods and forests. Grey squirrels also carry the squirrelpox virus, to which they are immune, but which is deadly to red squirrels.
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.