Identifying Hazel Bushes | Identifying Nibbled Nuts | Taking Part   Identifying Nibbled Nuts   Small rodents (dormice, wood mice and bank voles) all open hazel nuts by nibbling a neat round hole in the shell. Other animals, such as squirrels and jays also open hazel nuts, but they either split the shell completely in half or make a jagged hole in it. Some insects make holes in the nuts, but these are less than 2 mm across.   If you find nuts with neat round holes in the shell about 8-10 mm (3/10 inch) across then they've probably been opened by small rodents. You can tell which species opened the nut by looking carefully at the edge of the hole using a magnifying glass (reversed binoculars or some camera lenses also work).   The dormouse carves a virtually smooth inner rim and the toothmarks are at an angle to the hole on the nut surface.   The wood mouse leaves parallel toothmarks on the inner rim and rough marks on the nut surface.   The bank vole leaves neat parallel grooves on the inner rim, but no toothmarks on the nut surface. Squirrels and birds simply crack the shells open leaving jagged edges or half-shells.