Short-tailed Weasel (Ermine)

A weasel stands on a rock and looks over its shoulder
Short-tailed weasels are mammals in Yellowstone National Park


Black track of a short-tailed weasel
Short-tailed weasel track

Scientific Name

Mustela erminea


  • 8–13 inches long, 2.1–7 ounces.
  • Typical weasel shape: very long body, short legs, pointed face, long tail.
  • Males about 40% larger than females.
  • Fur is light brown above and white below in summer; all white in winter except for tail, which is black-tipped all year.
  • Compare to long-tailed weasel and marten.


  • Eat voles, shrews, deer mice, rabbits, rats, chipmunks, grasshoppers, and frogs.
  • Found in willows and spruce forests.


  • Breed in early to mid-summer; 1 litter of 6–7 young per year.
  • Can leap repeatedly three times their length.
  • Will often move through and hunt in rodent burrows.
A wolf standing on a snowy bank near brown grass howls

Home to the largest concentration of mammals in the lower 48 states.

Last updated: October 21, 2020

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Mailing Address:

PO Box 168
Yellowstone National Park, WY 82190-0168



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