Dormice being essentially a nocturnal arboreal critter, is not the easiest to see, so you find evidence of them from hazelnuts or acorns they've been eating. It isn't foolproof, because although most dormice leave a reasonably smooth hole with small diagonal tooth marks on the inside rim of the hole, you do occasionally get a messy one, or a woodmouse who has a bit more finesse in feeding. You need a lens to see the marks clearly, plus you can't always tell how old the nut shells are - so could be last years or older.

Angharad