The Grey Squirrel (Sciurus carolinensis)
FACTS AND FIGURES
Recognition: Silver-grey, agouti (speckled) coat, with a brownish tinge on feet, face and along the back, especially in summer; tail conspicuously fringed white. Much larger than the red squirrel, which has uniform reddish-brown (not agouti) fur. Lacks the ear tufts that red squirrels have in winter. Head/body length: 24-28.5 cm. Tail length: 19.5-24 cm. Weight: males 0.44-0.65 kg; females 0.4-0.72 kg (about twice the weight of the red squirrel).
Lifespan: females live on average slightly longer than males, up to 5 years (or exceptionally 6.5 years), and males live around 2-3 years (or exceptionally 6 years). But this difference may be related to residency more than mortality. Diet: Large seeds of trees such as oak, beech, hazel, sweet chestnut and walnut. When these supplies run out in early summer grey squirrels turn to a variety of flowers, buds, shoots, pine cones, fungi, peanuts from bird feeders, birdsí eggs and young.
Grey squirrels are native to eastern North America, from Florida and Texas and north just into Canada. Introduced to about 30 sites in England from USA in 1876-1929; to 3 sites in Scotland from Canada in 1892-1920; and to 1 site in Ireland from England. Now widespread in England and Wales, central Scotland and the eastern half of Ireland, and still spreading. Grey squirrels are essentially animals of deciduous woodland, and are dependant upon the large seeds of such trees as oak, beech, hazel, sweet chestnut and walnut. In autumn, when abundant, these seeds are stored, often underground. Because deciduous fruit falls to the ground in autumn, grey squirrels spend much more time foraging on the ground, and burying fruits there, than red squirrels. They typically make a nest (drey) of twigs (cut, live from the tree, often with the leaves attached, unlike bird nests). Dreys are usually tucked in a fork against the trunk, though squirrels also use large holes in trees as drey sites. Grey squirrels' main predators include stoats, goshawks and foxes. Squirrels are diurnal, usually with peaks of activity in the early morning and late afternoon. They are not territorial, but share home ranges and temporally abundant food sources. Grey squirrels reach densities of 2-3/ha, even as much as 8/ha, in deciduous woodlands; these are much higher densities than red squirrels in deciduous woodland. In conifers, both grey and red squirrels reach densities around 1/ha, though the density of grey squirrels may then depend on the proximity of some deciduous tress. The female can have two litters a year, in early spring and summer. Young squirrels are born blind and hairless, in litters of 3-4, after a gestation of 44 days. Lactation lasts up to 10 weeks, though the young start to take solid food after about 8 weeks. They can breed at 10-12 months old.
Grey squirrels are serious pests of forestry, especially stripping the bark of thin-barked species such as beech and sycamore. This behaviour is not fully understood; it seems to peak in early summer, at about the time when the first litter of young become independent, and at the time when tree fruits are least available. It can kill the top of the tree or distort its growth. They can also be serious pests in gardens and among horticultural crops. It has been illegal to keep grey squirrels (without a licence) since 1937, and it is illegal to release them into the wild... Grey squirrels can be trapped in cage traps and shot, or poisoned using warfarin (but only in counties where there are no red squirrels). Predicting when damage is most likely (early summer, after a good early breeding season) can make such control better targeted and therefore efficient. Drey- poking and shooting have also been used to control numbers in forestry, but are less efficient than cage-trapping.
Holm, J. (1987) Squirrels. Whittet Books, London.
Harris, S. & Yalden, D.W. (2008) Mammals of the British Isles: Handbook, 4th edn. The Mammal Society, Southampton.