Guide

Happening unseenMammals

Northern short-tailed shrews in winter

December to March

The northern short-tailed shrew does not hibernate. It stays active all winter, often in tunnels under the leaves and snow, and must feed often.

Why this time of year

Under the snow, the layer next to the ground stays near 32F even on subzero days, and shrews forage there out of sight.

How to notice it

  1. Look at the surface of a snowy field or woodland edge for small round holes, about an inch wide, with no tracks going in or out. Those are air vents for animals in tunnels below.
  2. Stand still and look along a stone wall or log where leaf litter meets snow. Do not dig or poke.
  3. On a quiet day, watch for a fox pouncing nose-first into snow. It is often listening for a shrew or mouse moving underneath.

Try this with kids: Find a small round hole in the snow and draw it. Which animal do you think is breathing down there?

Phrase to know: “Subnivean zone” means the narrow air pocket between the ground and the bottom of the snow.

Safety

  • Look, do not touch. If you come across a dead shrew or any small dead animal on a trail, leave it alone and keep kids and dogs away from it.
  • Shrews are not something to catch or handle: they bite, and the bite can be painful. Do not dig into snow tunnels or burrows.

Sources

  • massaudubon.orgMass Audubon: subnivean zone stays near 32F when air is below 0F; shrews among animals that depend on it; 'mouse holes' in snow are air vents; foxes dive for a mouse or shrew. Does NOT say the holes are shrews' specifically.
  • animaldiversity.orgUMich Animal Diversity Web: active year round day and night; tunnels through leaves, plant debris and snow; submaxillary glands produce toxic material that subdues prey.
  • trails.acton-ma.govActon MA conservation newsletter (secondary): subnivean layer near 32F; inch-wide holes with no tracks are vents; short-tailed shrews common in MA, constantly searching for food, jaw-gland venom.
  • alleghenycounty.usAllegheny County park fact sheet (secondary): subnivean runways; higher survival in snowy winters; winter food consumption about 43% higher than summer.

Checked against these sources on October 20, 2026.

In the guide for December, January, February, March

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