On finding this nibbled hazelnut, I was at first excited at the possibility that it might have been discarded by dormice. The toothmarks on the rim are at right-angles to the hole, and there are scratches around the nut surface. However, comparison with below handy guide from afanforestpark.co.uk points to woodmouse as the more likely culprit.
The woodmouse is widespread throughout Britain, and adapts to most habitats.
We will continue to examine partial nuts in the search for evidence of small furry friends.