Ermine are carnivores that consume mainly small mammals, especially voles (Microtus spp., Clethrionomys spp.) and mice (Peromyscus spp). Shrews and rabbits may also be taken and occasionally other small vertebrates and insects. Ermine foraging strategies are particularly well-adapted to northern environments where prolonged snow cover gives small predators, able to access under-snow tunnels, a competitive advantage, and where voles are the most abundant prey species. On Kodiak Island, Alaska, resident tundra voles (Microtus oeconomus) provide the bulk of ermine food supply, although these ermines have also been observed taking fish from a river.