Ecology & distribution
Squirrel Ecology
Eurasian red squirrel, Sciurus vulgaris
Red squirrels are the UK’s only native squirrel and recolonised the land after the last ice age. Their survival is threatened mainly by competition and disease transmission from introduced grey squirrels.
- Length: 18-24cm
- Tail: 17-18cm
- Weight: 100-350g
- Average lifespan: 2-5 years
- Physical features: coat and tail vary from red to black, body has a pale underside – but fully melanistic and albino varieties exist. Often with tufts on the ears, which they moult at different times of year.
- Native range: Europe and Siberia
- Habitat: woodland, heathland, moorland, parks, gardens – they create dreys (nests) of interwoven twigs, lined inside with soft materials such as moss, leaves, grass and fir.
- Diet: mainly seeds and nuts, supplemented by plant material, fruits, fungi and occasionally bird eggs.
- Breeding: mating begins in January and a litter of three to four kittens are born in March. A second litter can be born in July/August if females have enough food.
- Population: ~287,000 in Britain, down from 2.5 million over 100 years ago.
- Status: classed as endangered on The Mammal Society’s Red List for Britain’s Mammals. UK protection under the Wildlife and Countryside Act, 1981. Priority Species in the UK Post-2010 Biodiversity Framework.
- Threats: competition from invasive non-native grey squirrels, diseases – especially squirrel pox linked to grey squirrel spread, habitat destruction, road traffic accidents, predators.
Eastern grey squirrel, Sciurus carolinensis
Grey squirrels are not a UK native. They were introduced from North America to sites in England and Ireland between 1876 and 1929. They are classed as invasive due to their negative impacts on red squirrels and trees.
- Animal: mammal
- Length: 24-29 cm
- Tail: 19-24 cm
- Weight: 400-650g
- Average lifespan: 2-5 years
- Physical features: generally silver-grey coat, sometimes with brown shading to face and feet, and a pale underside – but fully melanistic and albino varieties exist. Tail has an outer fringe (halo) of white hairs.
- Native range: eastern North America
- Habitat: woodland, heathland, moorland, parks, gardens – they create dreys (nests) of interwoven twigs, lined inside with soft materials such as moss, leaves, grass and fir.
- Diet: mainly seeds and nuts, supplemented by plant material, fruits, fungi and occasionally bird eggs.
- Breeding: mating begins in January and a litter of three to four kittens are born in March. A second litter can be born in July/August if females have enough food.
- Population: estimates of 2.7 million in Britain, but this is thought to be an underestimate.
- Status: classed as an invasive non-native species in the UK and an invasive alien species in Europe. It was moved outside its natural range by humans and has negative consequences for native biodiversity and the economy.
Distribution
The UK red squirrel population is now as low as 287,000 individuals. Many (75%) of them are found in Scotland.
Most red squirrel survival relies on active management by organisations, volunteers and land managers to remove their main threat – introduced grey squirrels. Although some areas have natural barriers that prevent grey squirrel invasion, including islands like the Isle of Wight and Brownsea Island.
Red declines
Grey squirrels outcompete red squirrels for food and habitat, and transmit deadly squirrelpox virus. Competition stresses and weakens the red squirrels, and reduces their ability to fight off disease and reproduce. Greys have now replaced red squirrels in large areas of the UK. Once grey squirrels move into a new area it is only a matter of time before the red squirrels die out.
In the presence of squirrel pox, red squirrels die off 17-25 times faster. Grey squirrels are carriers of the virus, which they rarely contract but can be reservoirs for high concentrations of the disease. Squirrel pox outbreaks in red squirrel areas are generally linked to grey squirrel encroachment and disease transmission.
Grey incursions
At least 2.7 million grey squirrels now live in the UK. They are spread across large areas of England, Wales, the Scottish Lowlands, Northern Ireland and Ireland. They also live at higher densities than native red squirrels.
Grey squirrels are resistant to the tannin found in unripened nuts like acorns. Whereas red squirrels suffer from tannin poisoning, so have to wait until acorns ripen to eat them – when the tannin is less. Grey squirrels decimate this important food source early in the year, so outcompete red squirrels in broadleaved woods. This pushed red squirrels into areas with more coniferous trees, as they exploit the smaller cone seeds more easily than grey squirrels. Although this does not stop grey squirrels slowly invading these areas over time.
Red squirrels can live in a variety of different habitats as long as grey squirrels are not present, including urban areas with gardens and parks. Conservation efforts to remove grey squirrel populations are important for maintaining and expanding red squirrel populations.
Grey Squirrel Management
Learn how grey squirrel management helps protect UK forestry and the endangered red squirrel species.
Red Squirrel Conservation
Learn why red squirrels are classed as endangered in the UK and what’s being done to reverse the problem.
Tree Damage
Find out how Grey squirrels negatively impact the health of the UK’s trees and woods through bark stripping.
Squirrel Pox & Diseases
Learn how squirrel pox and other diseases can be devastating for the endangered red squirrel population.
Donate to help our work
Support the UK Squirrel Accord's work to protect red squirrels and trees, and effectively manage grey squirrels. This includes research to develop an oral contraceptive for grey squirrels.