As the leaves begin to fall from the trees it becomes easier to spot squirrels. They are currently putting on weight ready for the winter ahead and may be burying nuts in the hope of finding them later. Our native red squirrels are now officially classified as Endangered by our new Red List, having virtually disappeared across most of England and Wales.
In Scotland and Ireland red squirrels have fared a little better, particularly in areas of extensive coniferous forest which provides habitat much less favourable to grey squirrels. Sadly, the policy establishing broadleaved woodland around the perimeter of conferous plantations, in efforts to lessen the ecological and visual impacts, has back-fired – at least for red squirrels – because of the habitat it provides for greys. Grey squirrels carry squirrel pox virus, and this has played a major role in the decline of the red squirrel. However, other factors are important too. For example, as a child, I regularly saw red squirrels on woodland walks in Lancashire where I grew up. Most of those woodlands no longer exist or are reduced to tiny fragments criss-crossed by ring roads that link housing estates and out-of-town shopping centres.
Grey squirrels now outnumber reds by around 10:1 and, with their bold habits and propensity for visiting bird feeders, are a regular site in parks and gardens across much of Britain and Ireland. They were introduced from the USA to several sites in Britain in the 1870s, and to just a single site in Ireland (County Longford) in 1911; serving as ornamental additions to stately homes and parks. Although we tend to think of grey squirrels as a super-adapted invader, recent genetic research shows that much of their movement across the country, continuing to the present, has been mediated by people. For example, an isolated squirrel captured in 2010 in Northumberland, where red squirrels still dominate, was from Edinburgh rather than from the nearest grey squirrel population. Perhaps we should not be surprised by our propensity to meddle with nature. The Victorians were so successful with their hunting campaign on red squirrels — then seen as a pest that threatened forestry, as well as a handy source of fur to decorating women’s hats — that they virtually eradicated the entire Scottish population and had to reintroduce the species from Scandinavia. Historical evidence similarly records a thriving red squirrel trade in London markets.
We are now asking the public to help us monitor the status of squirrels. Thanks to the efforts of initiatives like Red Squirrels United, we are beginning to get a better understanding of red squirrel populations. However, we still need more data. And for grey squirrels, we frankly know very little because people tend not to bother reporting their sightings of species they consider common. So next time you are out on a walk, whether in the countryside or in an urban park, please remember to take the free Mammal Mapper app on your phone, and record any squirrels you see along the way.
by Professor Fiona Mathews, Chair of the Mammal Society and Professor of Environmental Biology, University of Sussex
Signorile AL, Wang J, Lurz PW, Bertolino S, Carbone C, Reuman DC. Do founder size, genetic diversity and structure influence rates of expansion of North American grey squirrels in Europe?. Diversity and Distributions. 2014 Aug;20(8):918-30.