Gray squirrels are an invasive species in the UK, introduced from North America in the 1870s. They are a problem for wildlife, including the endangered red squirrel, which they outnumber. They also carry a disease called smallpox that doesn’t affect them but can kill reds. They were originally used as ornamentals to decorate the gardens of stately homes, before the damage they caused was realized and their release was banned in the 1930s. Gray squirrels are also a threat to trees, stripping their bark and weakening them. They are a particular problem for broadleaf species including oak, which are ecologically important because they support so many other species. It is estimated that the UK is home to around 3 million of the invasive rodents. Scientists are trying to find ways to keep the gray population in check and now positive results have been released by the UK Squirrel Accord after a trial of oral contraceptives, which could be used to stop the mammals from breeding. The contraceptive is in production by the Animal and Plant Health Agency (Apha), with further testing being carried out to ensure it is safe and effective. To stop other species ingesting the drug, the scientists designed a special feeding funnel. It has a weighted door that will exclude most other wildlife while allowing more than 70% of the local gray squirrel population to access and eat from them. Apha is testing different methods to keep red squirrels out of feeders so that the contraceptives can be placed in areas where both types of squirrels are present. So far, research shows that body weight could be used to distinguish between gray and red. No oral contraceptives have been used in the field at this stage of research. Environment Secretary Richard Bennion said: “The gray squirrel is an invasive species that causes untold damage to the British countryside, where these pests continue to destroy our young broadleaf trees such as oak, stripping bark and disrupting nature’s delicate balance. and biodiversity. while reducing our ability to deal with climate change. “That’s why we continue to support the UK Squirrel Accord and Apha as this important oral contraceptive research shows promising signs that it could help eradicate the gray squirrel in the UK in a non-lethal way, as well as recovery of our beloved red squirrel. “ Other methods that have been used to try to reduce gray squirrel numbers include the release of pine ferrets in certain forested areas. These predators scare and eat gray squirrels. However, shy ferrets would not colonize urban areas that are gray squirrel strongholds, so as long as woodlands continue to be covered by urban gray squirrels, other methods – including contraceptives – will be needed to control populations. Gideon Henderson, chief scientific adviser at the Department for Environment, Food and Rural Affairs, said: “Fertility control can be an effective method to complement other approaches to wildlife management. This … study aims to produce an immunocontraceptive that can be administered orally to gray squirrels via a species-specific delivery mechanism. “This innovative research has great potential to provide an effective, easily implemented and non-lethal method for managing gray squirrel populations. It will help red squirrels – native to the UK – to expand back into their natural habitats, as well as protect UK woodlands and increase biodiversity.”
