A weapon that could help red squirrels in their Battle of Britain

Squirrel charities suggested that without conservation efforts red squirrels would disappear from almost all of England and Wales within ten years.

“KNOW the enemy” is a maxim attributed to Sun Tzu, an ancient Chinese military strategist. You must discover and then exploit your enemy’s weaknesses in order to prevail. The Red Squirrel Recovery Network (RSRN) has deployed such thinking in its battle against an invasive foe, Sciurus carolinensis—the grey squirrel. What is the weakness these ecologists are exploiting? The grey squirrel’s insatiable appetite for hazelnut butter.

Photograph: Naturepl.com

These creatures are in the crosshairs because of their impact on Britain’s own red variety: England now has only an estimated 39,000 red squirrels, compared with at least 2.5m greys. But the RSRN is confident it can turn the tide. The team’s researchers, from the government’s Animal and Plant Health Agency, have been lacing the hazelnut butter to develop their latest secret weapon: an irresistible contraceptive bait. Its potency for impotency is proven and, after field trials in Northumberland, will be ready for the front lines. To ensure there’s no friendly fire the team have designed an ingenious feeder. The door to the bait opens only to weightier squirrels, thus allowing 90% of adult greys to access it, but not a single red.

Squirrel charities suggested that without conservation efforts red squirrels would disappear from almost all of England and Wales within ten years. Their American grey cousins, introduced in the late 19th century, are larger, smarter and compete more successfully for food and habitat. Paw-to-paw combat is rare, but greys are resistant to the squirrelpox virus which they (allegedly unintentionally) spread among red populations, with fatal consequences.

Until now conservation efforts have focused on culling grey squirrels—a lethal but expensive tactic. It is hoped that the contraceptive bait and discriminative feeders will prove to be a scalable, more humane method of hobbling the enemy. The public are being urged to help intelligence and surveillance operations by logging sightings of squirrels on an app to support the project’s data team. The £4.9m ($6.6m) received from the National Lottery will fund the five-year master plan.

The RSRN is one of 26 conservation projects shortlisted for the Great British Wildlife Restoration Award, the winner of which will be decided in early 2026. The schemes range from Project DUNG, helping the country’s 60 species of dung beetle, to one aiming to save the glutinous snail, now confined to just one lake in North Wales. Such creatures rarely steal the limelight but are just as deserving of it as their exotic counterparts, says Nicky Needham, Head of Conservation at BIAZA, a professional body for British and Irish zoos and aquariums.

The plight of native species, especially the plucky red squirrels and their displacement by arrivals from overseas, resonates with an increasingly watchful British public. Fully 88% of Britons say they are concerned about the country’s reduction in wildlife. Britain has the most depleted biodiversity of any G7 country, according to an index produced by the Natural History Museum in London. Though red squirrels are not on the verge of extinction around the world (many stable populations thrive across Europe), their predicament in Britain is serious. So too is their allies’ hazelnut butter.