Grey squirrel spread is our fault

Humans helped grey squirrels disperse quickly across the UK.

Grey squirrels have had a catastrophic impact on our native reds – they outcompete them, and spread the lethal squirrel pox virus.
Grey squirrels have had a catastrophic impact on our native reds – they outcompete them, and spread the lethal squirrel pox virus.

Grey squirrels are not quite the aggressive invaders we thought. New research shows that their rapid spread across the UK depended on human help.

Advertisement

Genetic analyses show that Britain’s grey squirrels consist of a mosaic of rather inbred, isolated populations.

This suggests that, rather than spreading in a mass invasion front, greys were transported around the country by people.

Aberdeen’s grey squirrels are most closely related to populations from Hampshire, for example.

Other populations can be traced back to animals distributed as gifts by the 11th Duke of Bedford from Woburn Abbey in the early 1900s.

So, does this mean that the Scottish Highlands, the last major stronghold of red squirrels, will be safe from invasion if human-mediated dispersal can be prevented?

Not according to Lisa Signorile, who led the research at Imperial College London. “Grey squirrels expand anyway, just at a much slower rate than previously thought,” she said. “Besides, it is nearly impossible to stop accidental translocations.”

Indeed, Signorile has confirmed the genetic origin of a squirrel released in 2010 on Skye, a grey-free island, having reportedly travelled from Glasgow under a car bonnet.

Source Diversity and Distributions and Biological Conservation

Understand grey squirrels

Advertisement

Read more wildlife news stories in BBC Wildlife Magazine