Red squirrels have been replaced over a large part of Great Britain by the non-native grey squirrel, introduced from North America in the late 19th century. Today, the British population of red squirrels (approximately 287,000) is mostly restricted to Scotland, northern England and some offshore islands.
This fragmented distribution is bad news for conserving red squirrels, but provides an interesting case study for scientists. Given the different climate and habitats the remaining red squirrels live in, and the duration of their isolation from one another (many decades in some cases), might these squirrels have developed anatomical differences as other separated populations of the same species elsewhere?
