Red Squirrel Reintroductions
ZSL has been involved in the reintroduction of red squirrels in the UK to bolster the declining populations. These declines have been due primarily to the introduction of the grey squirrels from North America in the nineteenth century, bringing squirrel pox with them as well as out-competing our native reds.
The red squirrel (Sciurus vulgaris) is a European rodent which has declined dramatically in the UK since the introduction of grey squirrels (Sciurus carolinensis) at the end of the nineteenth century. Their rapid decline has been attributed primarily to the susceptibility of red squirrels to the squirrelpox virus, which the grey squirrel harbours but is immune to and which gives the greys a competitive edge over the reds.
Disease monitoring of red squirrels after reintroduction highlighted the severe effects of squirrel poxvirus disease, in areas where grey squirrels are present, to the red squirrel population
Scientists led by the Zoological Society of London have identified eight cases in which free-living red squirrels have survived infection with the squirrelpox virus by mounting an immune response. Their research has been published in the peer-reviewed journal EcoHealth. This finding provides hope that the red squirrel might have a chance of survival in the long term.