The grey squirrels warning was first issued in the UK in December 2025, and new concerns have emerged.
UK homeowners are being warned to take urgent action this winter after experts sounded fresh alarm bells about the growing threat posed by grey squirrels, which can infiltrate roof spaces, damage electrical wiring, destroy plumbing systems, and wreak havoc on garden ecosystems if left unmanaged. The warning, issued in December, highlights both the immediate domestic risks these animals pose and their far-reaching environmental consequences across Britain’s woodlands and wildlife.
Grey squirrels are a familiar and often charming sight in British gardens, but the picture they present is deceptively benign. Originally native to North America and Canada, they were introduced to Britain during the Victorian era to decorate the grounds of stately homes. Since then, the population has swelled to an estimated 2.7 million individuals across Great Britain, making them one of the most numerous invasive non-native species on British soil. Their impact on native ecosystems has been severe.
The greatest ecological casualty of the grey squirrel’s spread has been the native red squirrel, now classified as endangered in Great Britain. In England, only around 38,900 red squirrels remain, confined largely to isolated populations on the islands in Poole Harbour, the Isle of Wight, and fragmented areas of northern England. The mechanism of displacement operates on two levels. Grey squirrels are larger and more robust, allowing them to out-compete reds for food and territory. When grey squirrels move into a new area, red squirrels can be completely replaced within 15 years. The second mechanism is the squirrel pox virus, which greys carry without suffering any ill effects but which is almost invariably fatal to red squirrels, typically killing them within two weeks of infection. Where the virus is present, grey squirrels can drive out red populations approximately twenty times faster than through competition alone.
For woodland managers and foresters, grey squirrels represent a serious and costly problem in their own right. A Forestry Commission survey found squirrel damage present at 16 percent of one-hectare sites across England, with the south-west and Yorkshire and the Humber recording the highest rates of bark stripping damage. A separate assessment of at-risk woodlands found grey squirrels had damaged every single sycamore tree examined, 66 percent of beech trees, and 30 percent of oak and sweet chestnut specimens.
The economic cost of this damage to woodlands in England and Wales has been estimated at £37 million per year when factoring in reduced timber value, lost carbon revenue, and the cost of control measures themselves. Over a 40-year horizon, the Royal Forestry Society has projected that figure could reach £1.1 billion.
For homeowners the threat is more immediate and personal. Grey squirrels frequently gain entry to loft spaces through loose eaves, damaged soffits, and overhanging tree branches. Once inside, they gnaw through timber, electrical cables, and plastic plumbing pipes, creating fire hazards and structural damage that can prove extremely costly to repair. They typically produce their first litter of the year in February, meaning the winter months are precisely when they are most likely to seek out warm, sheltered spaces in which to nest.
Professional house buyers Gaffsy are advising any homeowner who suspects grey squirrels may have entered their roof space to contact Environmental Health immediately rather than attempting to handle the problem themselves. Practical prevention measures include repairing damaged eaves and soffits, installing durable wire mesh over potential entry points, and cutting back tree branches that provide easy access to the roofline.
In gardens, grey squirrels deplete winter food supplies at bird feeders that are intended to support struggling overwintering species including robins, which rely on garden food stations when insects and berries become impossible to find in frozen ground. Research carried out by the Game Conservancy and Wildlife Trust found that grey squirrels reduce fledging rates for native woodland birds by an average of 15 percent. They also consume the eggs and chicks of songbirds and raid orchards, market gardens, bulb plantings, and newly sown seeds.
The UK government has published a five-year grey squirrel policy statement through the Forestry Commission and Natural England, committing to financial incentives for landowners, expanded volunteer training programmes, and continued scientific research into novel population management methods including gene editing tools designed to spread female infertility through grey squirrel populations.