Following the introduction of the Eastern grey squirrel from North America in 1876, the UK's red squirrel population declined markedly as it struggled to compete for food and habitat.
However, the smaller red is now protected by European legislation and efforts have been made to safeguard the species through schemes like secret breeding stations and careful forest management.
Indeed, Anglesey has become safe haven for red squirrels thanks to a successful reintroduction project.
Numbers on the island had dropped to just 40 in 1998, but a combination of grey squirrel eradication and reintroduction of the red has meant that numbers have now soared.
While the grey is very common and well known in towns across Wales, the red is a very rare spot in the wild.
However, it's still a very recognisable species with its distinctive red coat (which turns thicker and darker in winter) and long ear tufts. It is about 19 to 23 cm in body length with a tail of 15 to 20 cm.
By contrast the grey is larger (25 to 30 cm in body length) and heavier and its coat is grey/tan in colour.
Tips for spotting red squirrels
- You have a better chance of seeing red squirrels if you look for them in the morning or late afternoon.
- Try not to make too much noise and look up into the trees where they spend most of their time.
- Listen for the falling material discarded by squirrels as they eat seeds.
- Look for evidence of squirrels feeding around pine trees - they eat pine cones in a very distinctive way.
- In autumn look near sweet chestnut and beech trees - they like the nuts these trees produce.
- Stay perfectly still if you spot one so as not to scare it away.
Try one of the walks from Derek's latest walking series on BBC One Wales.
Find out about the wildlife you can find on your doorstep.