English red squirrels are in decline, having been displaced from most of England and Wales by American grey squirrels. Introduced in the 1800s, grey squirrels out-compete the native squirrel – not only are they able to use a wider range of food sources, they are also more aggressive. To make matters worse, they carry “squirrelpox“, which is fatal to reds. Sunday’s New York Times magazine carries a story by D.T. Max entitled “The Squirrel Wars” which talks about the decline of the red squirrel and the movement to try to save it. Or rather – two movements, one trying to protect the red squirrel, and another dedicated to killing grey squirrels.
Sadly, it’s a classic story of introduced species managing to displace natives. In fact – it may be too much of a classic. Given its provenance, it’s likely that it did a lot to shape ideas about competitive displacement between functionally similar species, and about the ills of introduced species. According to T.D. Max, the squirrelpox (also known as Squirrel parapoxvirus) makes coexistence between the two species impossible. Without it, reds would be able to survive in coniferous forests, where resource levels are too low to support the larger, more active and more gregarious grey squirrels.