Grey squirrels (Sciurus carolinensus) are native to the eastern United States and have spread to the western part of the country as well as to the Britain, Ireland, Italy and South Africa. Though not as widespread as rats, the grey squirrel has had marked impacts on its wooded habitat. When their usual diet of nuts, seeds, fruits and fungi is hard to come by, grey squirrels strip the bark off beech and sycamore trees. In areas where their counterpart, the red squirrel, is present, they outcompete them, causing red squirrel populations to dwindle. Grey squirrels can also carry the parapoxvirus, which causes a debilitating and deadly disease in the native red squirrel.