Their dense, velvety fur insulates them well. They dig through the soil and leaves to eat the many dormant insect pupae and larvae almost frozen in the soil. They eat small hibernating mammals such as voles. They attack mice and voles who also move about eating roots, seeds, and bark just under the snow. Finding enough food is very difficult, especially since it must eat more than it does during warm months.
Many shrews starve to death during the winter.
They do store up much fat during the explosion of insects during spring and summer. The lucky ones live long enough to reach spring's harvest of insects again. In some species, a third to a half of the shrews die of starvation during the winter months. No wonder some shrews have two or three litters during the warm season.