Abstract

The red squirrel (Sciurus vulgaris) is native to Europe, but in the UK it is being threatened by the spread of the alien grey squirrel (Sciurus carolinensis). Since its introduction to the UK from the USA in the mid 19th century the grey squirrel has relentlessly increased its range at the expense of the red squirrel such that at the present time red squirrels are found only in isolated populations in England and Wales with the vast majority (70%) of the remaining UK population being found in Scotland. Although competition clearly plays a role in the replacement of the red squirrels by the grey squirrels, in areas where the grey squirrels are known to be carrying a virus known as squirrelpox virus red squirrels are estimated to disappear much faster than in areas where the grey squirrels do not carry the virus.

Infected grey squirrels show no obvious pathological symptoms whereas infected red squirrels rapidly succumb to a disease characterised by scabby erythematous lesions on exposed surfaces of skin. It is not obvious how the virus is transmitted within the grey squirrels or indeed from the grey squirrels to the red squirrels.

Our current understanding of the virus and its relationship to other poxviruses will be discussed together with our views on the chances for survival of the red squirrel within the UK, outlining the strategies currently being undertaken for the conservation of this iconic British species.