Ermines are carnivorous.
They eat small mammals, especially voles, also shrews, shrew-moles, immature rabbits, chipmunks, deer mice, jumping mice, and house mice. Other prey include small birds, frogs, small fish, and earthworms. Forage widely day and night, above and below ground and snow, in rock areas, in snags, stumps, and logs. Pursue small mammals into their own tunnels, runways, and burrows. Search for, and pursue, then kill prey by biting at base of skull.