Tips on Tracks: This week short-tailed weasel, ermine

Posted: Friday, February 04, 2011

Name of animal: Short-tailed weasel, ermine (Mustela erminea)

Illustration By Richard Carstensen
Illustration By Richard Carstensen

General description: Tracks look like a series of colons written in italics. Each track is about the size of an adult thumb nail.

Where, when to look: These tracks can be found year round. Ermine use a wide variety of habitats in Southeast from tidal areas and beaches to high in the alpine. However, these small mammals are so light-footed, their tracks rarely show except in the snow or fresh mud.

Lookalikes, and how to tell them apart: Red squirrels are similar in size, but their snowshoe hare-like gait and rodent family feet (four toes on the front paws and five on the hind) differentiate them. The ermine’s slightly larger weasel cousins, the mink and marten, leave similar but larger tracks.

More about the short-tailed weasel: Like the snowshoe hare, the ermine’s coat turns white in the winter. They eat primarily voles, mice and shrews. The weasel family in Southeast (ermine, mink, marten, river otter, sea otter and wolverine) all have five toes on both the front and hind paws. Developed by naturalist Greg Streveler, the “rule of thumb” is a helpful way to differentiate weasels: tracks the size of a thumb nail belong to ermine, mink tracks stretch from the tip of the thumb to the first knuckle, marten and river otter tracks stretch to where the thumb meets the hand and anything larger belongs to the wolverine. Recent genetic studies indicate a fascinating diversity of ancient and relatively recent weasel lineages, scattered about the islands and mainland of Southeast Alaska. In fact, some may be distinct species.

• This tracks feature appears every other week during winter months and is compiled by members of Discovery Southeast, a local nonprofit offering a variety of programs for local youth aimed at educating and engaging students in their outdoor world. For more information on the organization, go online to

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