Red Squirrels are an endangered species in the UK with numbers falling dramatically over the last 100 years. This is because grey squirrels have been killing them by carrying a virus deadly to reds. By 1997 the numbers of red squirrels on Anglesey was close to extinction with less than 40 living in one woodland.

Work has been done to get rid of grey squirrels and increase the population of red squirrels on the island. Today 60% of Welsh red squirrels can be found on Anglesey. In 2016 the island was said to be free of grey squirrels.