It has been thought since the 1930s that grey squirrels were all the same, spreading across the country as one invasion front. After a century, genetics has proved that this isn’t correct. They are not that good at breeding and mixing – in fact there are clear signs of inbreeding.
Grey squirrels are not as crazy invaders as we think – their spread is far more our own fault.
So, really, they're not as bad as we thought... right?