New research has revealed for the first time the catastrophic effect of a deadly virus on Britain's native red squirrels.
The research shows that squirrel poxvirus is threatening to wipe out red squirrels in some of the areas in which they remain in northern England within 10 years. In areas where the virus has been detected, the rate of decline in reds is 17-25 times higher than in places where there has been no outbreak.
Until now the reds' main survival challenge was believed to be competition with grey squirrels over resources. However, this research highlights the urgency for new conservation strategies for the red squirrel, a species that has been in Britain for the last 10,000 years and is protected under the UK's Wildlife and Countryside Act.
Researchers say that in the absence of a vaccine for the disease the only effective way of stopping the spread is to target grey squirrel control at the narrow entry points and corridors to England's 16 designated red squirrel refuges by killing the small numbers of greys that may come in.
Squirrel poxvirus is passed to reds by grey squirrels, and probably arrived to Britain with some of the greys that were introduced from North America over 100 years ago. The virus does not appear to harm grey squirrels, but is fatal to reds when they become infected.
Around 70 percent of greys in England have been exposed to the virus. They are thought to transmit it to red squirrels, which develop sores and ulcers on their face, feet and thighs, and they usually die within two weeks.
The research team - Newcastle University, Queen Mary, University of London, and other partners* - makes its recommendations for grey squirrel management in two academic journals, Epidemiology and Infection and Biological Conservation. The Mammals Trust UK and Forestry Commission, England (Kielder Forest District) funded the work.