Grey squirrel
Source: gov.uk (2025-10-30)

The grey squirrel (Sciurus carolinensis) is considered a woodland pest due to the damage they cause to trees. Learn more about their impact on trees, your management options and how to control their access to individual trees.

Area and status

Area

The grey squirrel is a non-native species first introduced to the UK from North America in 1876. The UK grey squirrel population was estimated at 2.7 million animals in 2018, according to Natural England’s Joint Publication JP025 (https://publications.naturalengland.org.uk/publication/5636785878597632). The species is widely distributed across most of England, Wales, Northern Ireland, and the Scottish Lowlands.

Status

Unlike the red squirrel, the grey squirrel is not a protected species.

Associated treescapes

Types of treescapes where this mammal is typically found, along with the level of presence in different treescapes:
- upland broadleaved woodland (https://woodlandwildlifetoolkit.sylva.org.uk/advice-types-broadleaf) (frequently found)
- lowland broadleaved woodland (https://woodlandwildlifetoolkit.sylva.org.uk/advice-types-broadleaf) (most common)
- mixed plantation (https://woodlandwildlifetoolkit.sylva.org.uk/advice-types-conifer) (common)
- conifer (https://woodlandwildlifetoolkit.sylva.org.uk/advice-types-conifer) (frequently found)
- wood pasture, parkland and orchards (https://woodlandwildlifetoolkit.sylva.org.uk/advice-types-broadleaf) (common)
Ecosystem services and impacts on biodiversity

Grey squirrels are known for their negative impact on native red squirrels, through:
- direct competition for food
- displacement from preferred habitat
- the spread of squirrel pox virus (https://www.daera-ni.gov.uk/articles/squirrel-pox-and-other-squirrel-diseases), a disease that is fatal to red squirrels but not to greys
While grey squirrels do prey on the eggs and nestlings of native birds, current evidence suggests that nest predation by grey squirrels occurs at rates too low to cause population declines in known prey species.

Grey squirrels may serve as important prey for pine martens and Eurasian goshawks, in areas where the species’ ranges overlap.

Identification and assessment of damage and risk to trees

The tree species most susceptible to grey squirrel damage include:
- sycamore or maple
- beech
- oak
- lodgepole pine
- Norway spruce
- Scots pine
Grey squirrels primarily damage trees through bark stripping. This can:
- occur anywhere from the base of the tree to the canopy
- create structural defects that degrade the tree’s quality
- increase the trees susceptibility to rot and disease
- kill the tree in severe cases
Trees between 10 and 50 years of age are most vulnerable to bark stripping. Grey squirrels may also damage young spruce and larch trees by biting off buds and shoots.

The economic impact of grey squirrel damage is significant. A 2021 Royal Forestry Society Joint Report (https://rfs.org.uk/insights-publications/rfs-reports/an-analysis-of-the-cost-of-grey-squirrel-damage-to-woodland/) estimated that grey squirrel damage in England and Wales could cost at least £1.1 billion over the next 40 years.

Managing grey squirrels in the landscape

Widespread use

Lethal control: shooting, trapping (https://www.gov.uk/guidance/protecting-trees-from-mammal-damage-technical-guidance/managing-mammals-in-the-landscape#lethal-control).

Occasional use

Enhance natural predation: nest (or den) boxes (https://www.gov.uk/guidance/protecting-trees-from-mammal-damage-technical-guidance/managing-mammals-in-the-landscape#nest).

In trial or development

Enhance natural predation: reintroduction or range expansion of predator species (https://www.gov.uk/guidance/protecting-trees-from-mammal-damage-technical-guidance#predation).

Non-lethal control: immunocontraception (https://www.gov.uk/guidance/protecting-trees-from-mammal-damage-technical-guidance/managing-mammals-in-the-landscape#immunocontraception).

Any control must be conducted in line with animal welfare legislation such as the Wild Mammals (Protection) Act 1996 and the Animal Welfare Act 2006. Lethal traps (i.e. permitted spring traps) should not be used when protected species are known to be present in the locality. This particularly applies where red squirrel, pine marten and dormice are concerned.

Managing trees in the landscape

Widespread use (or strong supporting evidence)

Adapting planting pattern and choice: landscape placement of new woods (https://www.gov.uk/guidance/protecting-trees-from-mammal-damage-technical-guidance/managing-trees-in-the-landscape#landscape).

Additional information, guidance and resources

Case studies, trials, and scientific research

Royal Forestry Society

Analysis of the cost of grey squirrel damage to woodland (https://rfs.org.uk/insights-publications/rfs-reports/an-analysis-of-the-cost-of-grey-squirrel-damage-to-woodland/).

Support, advice, and guidance

UK Squirrel Accord

A partnership of 45 signatories working together to protect the United Kingdom’s red squirrels and broadleaf trees from the negative impacts of grey squirrels: UK Squirrel Accord website (https://www.rsst.org.uk/uk-squirrel-accord/).

European Squirrel Initiative

Advice and guidance on how to promote the survival of the red squirrel throughout Europe through the control of the grey squirrel: European Squirrel Initiative website (https://www.europeansquirrelinitiative.org/).

Forestry Commission

A useful guide to distinguishing squirrel damage from that of other common mammals of English woodlands Forestry Commission grey squirrel guide (https://www.gov.uk/government/publications/grey-squirrel-and-deer-damage-to-trees-visual-guide).

Forest Research

Nearest neighbour method for quantifying wildlife damage to trees in woodland: Forest Research website (https://www.forestresearch.gov.uk/publications/nearest-neighbour-method-for-quantifying-wildlife-damage-to-trees-in-woodland/).

The National Forest

Grey squirrel activity and impact assessment documents: The National Forest website (https://www.nationalforest.org/grants-and-advice/woodland-management/grey-squirrel-impact).