Voles absolutely eat crocus bulbs, and they tunnel, so it is probably voles. Voles may rhyme with moles but they are quite unrelated. Moles are not rodents, and are carnivorous and do not eat plants at all. Voles are rodents, in fact closely related to mice.
Quite a few bulbs are either poisonous, like narcissus, or bad-tasting, like onion relatives. Probably to protect themselves from the damn voles.