UK Invasive Species – War of the Grey and Black Squirrels

red squirrel, and before the last quarter of the 19^th century they numbered in the millions and ranged across the whole country. Red squirrels are easily recognisable by their striking red coats, bushy tails and tufts of red fur on their ears. Their preferred habitat is conifer forest, where they live off pine cones, seeds, shoots and fruit. The red squirrel tends to be a solitary animal except during the mating season, when they build large nests called dreys in the forks of trees producing a litter of between 2-3 kittens in the spring. However, it is now estimated that there are as few as 120,000 red squirrels left in the wild, and the major cause of their decline was the introduction of grey squirrels into the UK.

black squirrel also arrived from the US in the late 19^th century, where they were kept as exotic pets in a private zoo in Bedfordshire. Some of these animals escaped from captivity, and in 1912 the first wild black squirrel was spotted in the environs of Letchworth, Hertfordshire. It is now estimated that there are more than 25,000 of them living in the UK, most of which are in the East Anglia region, and some scientists think that they could eventually become the dominant squirrel species in this country as there are more sightings of black squirrels being reported from other parts of the UK.

Grey and black squirrels are actually the same species, but a genetic mutation caused an excess of melanin to be produced in some squirrels that caused the black pigmentation of the fur. It is thought that having black fur could help the squirrels to survive in colder climates, as it absorbs heat more readily. Being so closely related, the grey and black squirrels can breed with each other, but when they do the black gene is dominant, which is another reason why they may eventually overtake the grey squirrels in numbers. There has been a major research project undertaken on the spread of black squirrels by Anglia Ruskin University since 2004, where they have set up a website asking the public to report any black squirrel sightings they have made. So a seemingly successful invasive species, can in its turn be overtaken by a more recently introduced species, so that in a few years time we could all be watching black squirrels in our parks, and the grey squirrels, just like the reds, might well have been pushed out and be only surviving in small colonies in the remoter, more inhospitable parts of the UK.