The grey squirrel, which is native to North America, was introduced into the UK in the 19th century. It was brought over as an exotic species and was initially kept in private collections before being released into the wild. The grey squirrel quickly established itself and is now considered an invasive species, outcompeting the native red squirrel for resources and spreading disease. Efforts are ongoing to control the population of grey squirrels and protect the red squirrel population.