Squirrelpox and the translocation of red squirrels

In recent years, there has been enormous enthusiasm for red squirrel reintroduction programmes in Great Britain

In recent years, there has been enormous enthusiasm for red squirrel reintroduction programmes in Great Britain as the range and numbers of this, much appreciated, native species tumbles in the face of an ever-successful expansion of the competitive grey squirrel.   

The first reliable record for grey squirrel reintroduction, imported from the Eastern USA, was in Cheshire in 1876. Other introductions followed, resulting in a relentlessly increasing grey squirrel population throughout the British Isles.

In the early 1900s, reports started to appear in newspaper articles and natural history newsletters of a ‘mange’ affecting red squirrels and many red squirrels were found dead with similar signs, especially in southern England. The first scientific work to try to explain the changing distributions of red and grey squirrel was published in the 1930s but it wasn’t until the 1990s that the true impact of the disease, known by this time as squirrelpox, was elucidated.  

Squirrel pox in the late 1990s

Through a series of complex epidemiological studies it became clear that the major reason for red squirrel decline in England, Wales and later, from the late 1990s onwards, in Scotland, was squirrelpox (see photo below) and that the grey squirrel harboured the virus causing the disease. 

Outbreaks of the disease still occur in mainland remnant populations of red squirrels where grey squirrels encroach, and despite sterling and sustained conservation efforts the range of the red squirrel continues to decline. In the face of this gloomy picture for red squirrel conservation, it is attractive to try any possible conservation solution and there has been sustained interest in red squirrel reintroduction.