Grey squirrels were introduced to Ireland from North America over a century ago. The species quickly established itself and rapidly spread throughout the country. They cause significant damage to certain tree types and pose a serious challenge to the continued existence of the native red squirrel.
Damage Caused by Grey Squirrels
Every year, grey squirrels cause millions of euro in damage to forestry, woodlands, country estates, stud farms and golf courses. They tend to attack beech, sycamore, elder and hazel trees between 10 and 40 years old, although this will vary depending on the tree type. They attack trees by first stripping the bark from around the trunk and branches (commonly known as bark stripping), discarding it, and then feeding on the soft vascular tissue underneath. This will most likely result in serious discoloration or the death of the tree. They are more likely to cause damage to trees between March and August, the period when the carbohydrates stored in the tree roots are flowing upwards to the branches and leaves.
The spread of the grey squirrel has been mirrored by a worrying reduction in the number of native red squirrels. Our native reds are simply out-competed by the larger and more robust greys, who have a more varied diet. Greys can also act as carriers of the parapox virus, which has a deadly effect on native red-squirrel populations.
In Ireland, grey squirrels are classified as vermin. The National Parks and Wildlife Management Service actively encourages control of their numbers. Effective control can best be achieved through a humane and structured program of shooting and trapping.