Red squirrels are driven toward extinction in England and Wales by squirrelpox virus carried by grey squirrels, causing a fatal disease that only affects reds.
Red squirrels dying from squirrelpox experience skin ulceration, lesions around the face and limbs, lethargy, and weight loss before death over 15-30 days. The disease causes prolonged suffering that is difficult to treat in wild animals. Individuals in fragmented conservation areas experience chronic stress from high predation pressure and limited habitat connectivity. Grey squirrel management programs are controversial but are considered by conservationists as essential to prevent total red squirrel extinction in England.