Grey squirrels, or their Latin name sciurus carolinensis, are native to eastern North America, where they are highly valued as the most prodigious and ecologically essential natural forest regenerator. These apparently valuable animals were introduced to Britain in 1876 as fashionable additions to country estates, but because grey squirrels compete for food and shelter with our native red squirrels and carry the squirrelpox virus (to which they are immune but which is fatal to red squirrels), they soon became the main threat to the survival of the native red population – it has been estimated that they now out-number the native red squirrels by 180 to 1. They also predate birds' nests and chicks and will strip the bark off trees, causing great damage. They are undoubtedly a problem in our community woodland, with which, at some point, we will have to deal.
However, squirrels' aerial gymnastics are always fun to watch. The grey squirrel builds itself a nest (called a 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. 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, and a squirrel will lie up in this in very cold weather. They will emerge now and then to search out hidden stores of food buried in the ground in autumn, well spread out. They are found by smell, rather than memory. Often these caches are not found at all and, later in the year, the seeds may germinate and grow, thereby helping the dispersal of trees.
Grey squirrels breed for the first time at a year old. 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 (the 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 youngsters 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 old, 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 but, if it is crowded, they will be chased away to look for less crowded feeding areas.
Ed: Photographs courtesy of John Daines and Keith Barker