I’ve blogged before about invasive species and the far-reaching impact on our eco-system and thought a post on the impact of the grey squirrel upon our native red would make an interesting post. The introduction of grey squirrels into the UK has had a devastating impact on our native trees and squirrels. Until the late 1800’s red squirrels were the only species in the UK but from the 1800’s to the 1930’s around 30 waves of grey squirrel were introduced into country estates as a novelty species. Today it is estimated there are two million grey squirrels and only 140,000 red squirrels left.
The main threat to the red squirrel is squirrel poxvirus which is not harmful to the grey, but fatal to the red. The virus, which was first identified in the 1980’s, can spread through contact with infected lesions or contaminated crusts, and can be carried by mosquitoes or contracted via a contaminated food source such as a bird or squirrel feeder. The disease is long and painful and resembles a rabbit with myxomatosis.
Greys also damage woodlands by stripping bark from the main stem and branches of trees. The damage to trees is prevalent from April-July, and is exaggerated after a strong breeding season. The greys discard the outer bark and eat the unlignified tissue beneath. Stripping bark is also an outcome of aggressive interactions between young squirrels. Around 5% of damaged trees will die. Greys tend to attack trees older than ten years which can support their weight, but are usually unable to penetrate the bark of very old trees.
Competition for food also places pressure on the native squirrel population. Red squirrels can only tolerate ripe acorns; greys can eat green acorns and will also raid stores, putting pressure on food supplies and often decimating supplies.
Reds are easily distinguishable by their flame coloured fur and ear tufts. They are located mainly in the north and Scotland; Yorkshire forms the boundary and thus is the focal point of much interest by conservationalists to observe if reds are retreating further north or returning south.
Locals in Yorkshire are currently encouraged to report their sightings of both red and grey by placing food and a sticky strip inside a pipe. When the squirrel creeps in, a few hairs from their fur remains behind. This data can be used to map squirrel populations and identify areas of support for the red colonies.
Controlling the grey squirrels and encouraging the reds is crucial to gain the rebalance. Keeping the red and grey squirrels apart and establishing new colonies of red squirrels is crucial to the survival of the reds. Last year red squirrels were spotted in towns in Anglesey after a successful project boosted the population from 40 to an estimated 500 reds.
Future habitat management is also important to support our red squirrel population. The Forestry Commission is working on a project to assess ways of designing and managing forests to develop a long term strategy that deters greys and encourages reds, including a pilot at Kielder Water. To find out more information about red squirrels in your region visit the Red Squirrel Survival Trust.
But the squirrel fight for dominance isn’t just limited to red v grey. The latest invader is the black squirrel.
- Look for chewed pine cones that look like chewed apple cores at the base of trees which may indicate red squirrel activity.
- There are an estimated 15,000 reds left in England.
- The main predators of red squirrels are birds of prey and pine marten. In some urban areas domestic cats can prey on red squirrels.
- Reds do not hibernate.
- Red squirrels build large nests, called dreys, often in the forks of tree trunks.
- The lifespan of a red squirrel is six years.
- Squirrels can swim.
- Females usually have 2-3 kittens but litters can be of up to 6 young, born 45-48 days after mating. Females bring up the young and are territorial over their brood.