The impact of Pine Martens
Native to Britain and Ireland the pine marten is a mustelid with relatives including the weasel, stoat, polecat and otter. It's about the size of a small domestic cat. Dietary studies have shown that pine martens are more likely to eat non-native grey squirrels than native red squirrels. This research has shown that where pine martens are thriving red squirrel numbers have increased and grey squirrel numbers decreased. Red squirrels are smaller and lighter than grey squirrels and can easily escape to small branches away from pine martens, whereas grey squirrels are larger and heavier and spend more time on the ground – making them an easier target for a hungry pine marten. Further useful information can be found on Jim Dixon's Pine martens and red squirrels blog.
Pine martens like woodland habitats, but they will also live in scrub, rocky areas and crags, the latter giving them a chance to use their supreme agility and climbing skills. Pine martens prefer to rest and breed above ground and frequently den in tree cavities, squirrel dreys and wind-throw. They will also use purpose-built den boxes and owl boxes.
For more information look at the Pine Marten Recovery Site