A lethal virus is threatening to wipe out some of Britain's last remaining red squirrel populations, conservationists said yesterday.
The squirrel poxvirus is spreading so fast that scientists believe some populations of red squirrels in the north of England may die out completely within 10 years. In areas where the virus has been detected, the decline of red squirrels was recorded as 17 to 25 times faster than areas free of outbreaks.
Red squirrels, which have been in Britain for the past 10,000 years, have suffered dramatic declines since the introduction of the grey squirrel from North America more than 100 years ago. Grey squirrels are believed to out-compete red squirrels for food, leaving them struggling to sustain their numbers. Researchers believe the virus is carried by grey squirrels. They are themselves unharmed, but pass it on to red squirrels.
In the absence of a vaccine, researchers believe the only way to protect the red squirrels is to cull grey squirrels on land leading to England's 16 designated red squirrel refuges. "It is vital we get this disease under control, especially as it is now threatening to spread across the border to Scotland, with severe consequences for red squirrel conservation there," said Peter Lurz of Newcastle University.
The researchers analysed public records on red squirrel populations in Cumbria and Norfolk, where the virus has been detected, and compared them with records in Scotland and Italy which have not been affected by the virus.
The records showed that in Cumbria, the amount of land red squirrels were seen on reduced by 76 sq km a year (29 sq miles) and 96 sq km in Norfolk. In Scotland and Italy the animals' range declined by 3.6 sq km and 4.4 sq km respectively.
Using computer simulations, the scientists showed a continuous cull of more than 60% of greys was needed to save the red squirrels.
The research appears in the journals Biological Conservation, and Epidemiology and Infection.