Key Identification Features
Grey squirrels have grey fur on their backs and sides with a white underbelly and a reddish chestnut coloured tinge all over in summer. They moult their coats twice a year, first in winter and then in summer but only moult their ear tufts and tail once yearly. The grey squirrel’s tail will have a white tip in summer before turning darker in winter. They are larger and have a more stocky appearance than the Irish red squirrel measuring up to 50cm in length which includes a long bushy tail of up to 25cm. Adult grey squirrels are similar in weight with the females being slightly heavier at 700 grams with males reaching up to 650 grams, both sexes will experience seasonal variations in their weight which is at its lowest in spring and can be 25% less than in Autumn when their main food source is abundant. The fore feet are four-toed with the larger hind foot having five digits measuring up to 7.5cm in length. Movement while on the ground is hesitant with bounding leaps in between periods of standing on the hind legs to scan their surroundings. Grey squirrels are a vocal species of rodent making numerous calls resembling a low tuk tuk noise when communicating, they also use foot stamping and tail flicking to signal other squirrels. They have excellent vision as their eyes are set in the sides of their heads allowing for a very wide field of view. The main distinguishing features which separate grey and red squirrels apart from their colour and size is that grey squirrel’s heads appears more rat like with smaller ears and no erect tufts of fur.
Grey squirrels can thrive in any area which provides their main food source of broadleaf tree seeds, these can be found in coniferous forests, deciduous woods, parks, large gardens and hedgerows but they prefer habitats of deciduous or mixed woodlands in Ireland. Most of their time is spent in the tree canopy with regular visits to the forest floor to forage. An individual grey squirrel will have a habitat range of around 10 hectares, which will contain a number of nests known as dreys. Summer dreys are open platforms in tree branches while more solid nests are constructed in winter for use by breeding females. Dreys are built with a hard outer layer of twigs lined with a soft inner layer of grasses and moss. The grey squirrel differs from its red cousins by building dreys some distance from the main trunk of the tree in forks in branches, they will sometimes use hollows in trees and old bird nests in winter.
Food and Feeding Habits
Grey squirrels are largely vegetation feeding on a wide variety of seeds, berries, fruits, nuts, roots and cereals which are provided within forests. They have a particular preference for the seeds of broadleaf tree species such as acorns, pinecones, hazelnuts and beech mast. They are opportunistic feeders and will raid any nearby vegetable gardens or agricultural fields. Fungi are a favored food source in damp woodlands as is wild honey and even birds eggs when they are available. Grey squirrels mainly forage in daylight hours and spend more time at ground level then red squirrels where they will store any extra food gathered in a series of hoards which are shallow holes dug in the ground. Grey squirrels do not hibernate in winter but in cold weather conditions will spend several days in the nest only emerging to visit one of their ground level hoards to feed.
Reproduction and Life Cycle
Grey squirrels are seasonal breeders with the main mating season usually beginning in December and lasting to mid summer. At this time males may travel long distances through several females territories in search of a mate. Males who are ready to breed will become more vocal and be involved in numerous fights for mating rights. Courtship is often frantic, typically the female will have one litter a year but if the winter period is mild than a second litter can be produced by the time the breeding season ends in mid summer. The average litter size will contain between two and seven young after a pregnancy which lasts for up to 45 days. The young squirrels are born naked and blind weighing only 15 grams and need to be weaned by their mother for ten weeks. If a second litter is produced the young will not be born until the first litter is fully weaned which is unusual for rodents. Young grey squirrels are cared for by their mothers only and will have gained their full independence after fifteen weeks. The mortality rate for grey squirrels can be as high as 70% in their first year of life but their chances of survival will greatly increase if they can make it through their first winter. Female grey squirrels generally live longer than males with a maximum lifespan of up to 7 years but most Irish squirrels only live to 3 years which is two mating seasons.
The grey squirrel has been recently introduced to Ireland. It is believed to have originated in North America with the current population having descended from a large release of squirrels in the midlands in the early 20th century. In Europe they are currently found in Ireland, Britain and Italy. In Ireland they are now distributed over most of the midlands, south, east and in some northern areas wherever there is suitable wooded habitats. They have not been as successful in the west due to the lack of suitable mixed and broadleaf forest habitats. The grey squirrel’s expansion in other countries where it has been introduced has not been as successful in Ireland due in part to the lack of large areas of remaining native deciduous woodlands and the widespread plantation of fast growing conifer tree species in the last number of decades which do not provide the grey squirrel with all it’s habitat and dietary requirements. Populations may be isolated and spread over large areas but where suitable habitats exist they can number up to 8 individuals per hectare. The main limiting factor in their distribution is the availability of broadleaf seeds which they rely on when cold weather periods arrive.
The grey squirrel, although a recent addition to Ireland’s mammal family has become an important part of forest ecosystems as they spread seeds, especially acorns in the autumn which is vital for broadleaved tree re-seeding and spread. They will not fully replace the red squirrel population due to coniferous forest habitats lacking in all of their dietary requirements although they can reduce red squirrel densities in all other habitat types. Their ability to more quickly adapt to different habitats and their opportunistic feeding tendencies has allowed them to spread to urban areas where they thrive on vegetable gardens and the seeds from bird tables, this will continue, allowing them to further expand their range in conjunction with increased urban sprawl in Ireland. In some areas where a population is large they can be considered a pest species due to their habit of feeding on the bark of young deciduous trees resulting in poisonings and trappings. The presence of grey squirrels can also be reduced in wooded areas that have been preserved mainly for the breeding and hunting of game birds as they will snatch the eggs of any ground nesting birds if the opportunity arises. Road kills now account for one of the main causes of grey squirrel deaths in Ireland today.