Weasels

Identification | Biology | Damage ID | Management | Resources

Figure 1. Short-tailed weasel (Mustela erminea) in summer coat. Photo courtesy of Naturespicsonline.com.

Learning Objectives

  1. Explain elements about the biology of weasels that are important for their control. 
  2. Explain management options available to clients.  

Identification

Weasels belong to the Mustelidae family, which also includes mink (Neovison vison), martens (Martes americana), fishers (M. pennanti), wolverines (Gulo gulo), badgers (Taxidea taxus), river otters (Lontra canadensis), black-footed ferrets (Mustela nigripes), and four species of skunks (Mephitis spp., Conepatus leucontus, Spilogale putorius). 

Legal Status

All 3 weasels generally are considered fur bearers under state laws, and a trapping season is normally established for fur harvest. Check local and state laws before undertaking weasel control measures. 

Physical Description 

Although members of the weasel family vary in size and color, they usually have long, slender bodies, short legs, rounded ears, and anal scent glands. Weasels, like all mustelids, produce a pungent odor. When irritated, they discharge the odor, which can be detected at some distance. 

A weasel’s hind legs are barely more than half as long as its body (base of head to base of tail). The weasel’s forelegs also are notably short. These short legs on a long, slender body may account for the long-tailed weasel’s (Mustela frenata) distinctive running gait. At every bound the long body loops upward, reminding one of an inch-worm.  

Male weasels are distinctly larger than females. The long-tailed and short-tailed (M. erminea) (Figure 1) weasels have a black tip on their tails. The least weasel (M. nivalis) lacks the black tip (Figure 2). All weasels have a white winter coat (Figure 3).  

Figure 2. Identification of weasels.
Top: least weasel. Image by Prevention and Control of Wildlife Damage (PCWD). 
Figure 3. Weasels have white coats in winter. Photo courtesy of naturespicturesonline.com. 

Species Ranges

Three species of weasels live in North America. The most abundant and widespread is the long-tailed weasel (Figure 4a). Some that occur in parts of Kansas, Oklahoma, Texas, and New Mexico have a dark mask and are often called bridled weasels. The short-tailed weasel occurs in Canada, Alaska, and the northeastern, Great Lakes, and northwestern states (Figure 4b), while the least weasel occurs in Canada, Alaska, and the northeastern and Great Lakes states (Figure 4c).  

Figure 4a. Distribution of the long-tailed weasel in North America. Image by PCWD. 

Figure 4b. Distribution of the short-tailed weasel in North America. Image by PCWD.

Figure 4c. Distribution of the least weasel in North America. Image by PCWD. 

Voice and Sounds

Weasels produce four basic vocalizations, which include the “chirp,” “hiss,” “trill,” and “squeal.” The “chirp” is a loud, harsh sound emitted when an animal is disturbed. The “hiss” is a fright sound that indicates fear or threat. The “trill” is sounded during friendly encounters between males and females. The “squeal” has been heard in stressful situations, probably in response to pain.  

Tracks and Signs 

In the typical bounding gait of the weasel, the hind feet register almost, if not exactly, in the front foot impressions, with the right front foot and hind feet lagging slightly behind. The stride distance normally is about 10 inches.