A field trial for an oral contraceptive designed for grey squirrels is expected to commence later this year or early next year. The Red Squirrel Survival Trust is jointly funding this trial, which is being conducted by the government's Animal and Plant Health Agency.
The contraceptive is intended to be delivered to grey squirrels using a 'hopper' system, where the squirrels lift a lid to access the contraceptive. This method is designed to be specific to grey squirrels, as they typically weigh around 500g, approximately twice the weight of red squirrels.
Red squirrel populations in the UK have significantly declined, from an estimated 3.5 million to less than 300,000. In England, the Woodland Trust estimates there are only 39,000 red squirrels remaining, while the Save Our Reds campaign suggests a figure of 15,000.
Grey squirrels, introduced from North America in the 19th Century, now number between 2.5 million and 2.7 million in the UK, according to Graham Paskett from the Red Squirrel Survival Trust. They outcompete red squirrels for habitat and food, and carry squirrel pox, which is fatal to reds.
Jackie Foott from the British Red Squirrel conservation group stated that reds and greys cannot coexist. She explained that grey squirrels are a non-native, invasive species that cause damage to trees, crops, and properties, estimated at £40 million annually to forests and forestry services.
Currently, lethal control through shooting or trapping is the primary method for managing grey squirrel numbers. The reintroduction of pine martens is also considered helpful, as they prey on grey squirrels, which are less adept at avoiding them compared to native red squirrels.