Long-tailed Weasel - Mustela frenata
Largest and most widely distributed of the three Northern American weasels. Distinguished by its long, slender body and long neck. Longest tail of the North American weasels. During summer fur rich brown on the back and sides with yellowish-white under-parts, black tip on tail, and no whitish line down inside of leg. Acquires a white winter coat. Adult males noticeably larger than females. Total length: 11 to 16.5 inches. Weight: three to 12 ounces.
Short-tailed Weasel has white line down inside of leg and is smaller. Least Weasel does not have black tip on tail and is smaller. American Mink is nearly uniform dark brown. Marten is heavier and much larger.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Found in almost all land habitats near water. Has the broadest ecological and geographical range of the North American weasels. Prefers areas with abundant prey. Avoids dense forest, most abundant in late seral ecotones. Primarily nocturnal, but sometimes active during the day. Quite fearless and curious. Mainly terrestrial but can climb and swim well. Nests in old burrows of other animals. Occupies a diverse range of habitats. More prone to open country and forest openings than M. erminea. Common in intermontane valleys and open forests where M. erminea is absent. May occur up to alpine tundra (Hoffmann and Pattie 1968).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: mtnhp.org/requests
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
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- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Human Land Use
Recently Disturbed or Modified
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Recently Disturbed or Modified
More of a generalist than the Short-tailed and Least Weasels. Feeds mostly on small mammals up to rabbit-sized, but eats birds and other animals as well. Males: rabbits, tree squirrels, and ground squirrels. FeMales: mice and chipmunks. Dietary componenets overlap. Both sexes will occasionally use birds, herptiles, and insects (Jones et al. 1983).
Weasels will cache prey. This permits food storage without obesity, facilitating ability to pursue prey in narrow burrows. Males about 10 to 15% larger than females (Svendsen 1982).
Mates during summer, 205- to 337-day gestation; delayed implantation; young born during April; litter size four to nine.
- Literature Cited AboveLegend: View Online Publication
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- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
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- Additional Sources of Information Related to "Mammals"