FAQ: Does the presence of the grey squirrel always result in a decline in red squirrel populations?
This is found to be the case in most instances. Anatomical differences between red and grey squirrels mean that greys are more robust as a species. These differences allow greys to outcompete reds for food and habitat space. Greys are physically larger in size and, unlike reds, greys can feed on seeds with high tannin content, such as acorns, thanks to differences in digestive physiology. As a result, more food sources are available to greys and they tend to put on 20% in body weight over autumn, compared with 10% for reds. Greys also have higher juvenile survival rates. In areas where red and grey squirrels exist together; the presence of greys tends to result in a steady decline in red squirrel populations over time. This effect can already be seen in Scotland’s Central Belt where grey squirrel spread has resulted in the almost entire disappearance of our native reds.
The only habitat in which red squirrels seem to have an advantage over grey squirrels is large conifer forests which don’t contain large-seeded broadleaved trees, such as oak, beech, hazel and chestnuts. Forestry Commission Scotland has just identified 18 such sites, called ‘red squirrel strongholds’ which will be managed over the long term to give red squirrels a competitive advantage over any grey squirrels which reach the site.
