Sign: bark gnawed at foot of tree; burrow entrance at tree roots Photograph: Nature Picture Library/Britain on View RM
Sign: small, poo-like pellets of bone, fur and feathers Photograph: Rick Wylie/Flickr RM
Sign: long, vertical strips chewed off tree bark Photograph: Alamy
Sign: hole nibbled through nuts; scales bitten off fir cones Photograph: Alamy
Sign: small entrance to nest in tree trunk; nuts wedged in bark Photograph: Ken Fisher/Flickr Open