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long-tailed weasel

Mustela frenata

What do they look like?

Long-tailed weasels have a long slender body and head. Their long bodies and flexible backs allow them to enter the burrows of rodents and other animals that are smaller than them. On average, males are larger than females. These weasels have long, bushy tails that make up about 50% of their total body length. Long-tailed weasels have a small, narrow head with long whiskers, and short legs. Their fur is composed of short, soft underfur covered by shiny guard hair. They are cinnamon brown in color with white under parts that have a yellow tinge. Long-tailed weasels have a black tip to their tail, even in their all white winter phase. This differentiates them from the smaller least weasel, which doesn't have a black-tipped tail. Twice a year these weasels shed their fur, once in the spring and again in the fall. They shed in response to changes in daylength. The coat of animals in northern populations is white in the winter and brown in the summer, while those in southern populations are brown year round. Head and body length ranges from 203 to 266 mm, tail length ranges from 76 to 152 mm.

  • Sexual Dimorphism
  • male larger
  • Range mass
    80 to 450 g
    2.82 to 15.86 oz
  • Average mass
    150.6 g
    5.31 oz
  • Range length
    203.0 to 266.0 mm
    7.99 to 10.47 in
  • Average basal metabolic rate
    1.344 W

Where do they live?

The range of long-tailed weasels includes most of North America, extending from just north of the United States-Canada border south throughout Central America to northern South America.

What kind of habitat do they need?

Long-tailed weasels have adapted well to the changes in environment caused by humans. Long-tailed weasels are found in temperate and sub-tropical habitats in North and Central America. These habitats range from crop fields to small wooded areas to suburban areas. They are not found in deserts or thick, dense forests. Their burrows and nests are made in hollow logs, rock piles, and under barns. Sometimes, instead of building a new nest, long-tailed weasels use rodent burrows.

How do they reproduce?

Mating for long-tailed weasels occurs in the mid-summer months. After copulation, implantation of the embryo is delayed and the egg does not begin to develop until March, making the total time that the female is pregnant around 280 days. Birth occurs from late April to early May, and the average size of the litter is six. Females mate in their first summer, but males wait until the following spring.

  • How often does reproduction occur?
    Long-tailed weasels mate once each year.
  • Breeding season
    Young are born from April to May.
  • Range number of offspring
    4.0 to 8.0
  • Average number of offspring
  • Range gestation period
    337.0 (high) days
  • Average gestation period
    280.0 days
  • Average weaning age
    36.0 days
  • Range age at sexual or reproductive maturity (female)
    3.0 to 12.0 months
  • Range age at sexual or reproductive maturity (male)
    3.0 to 12.0 months

At birth, young weasels weigh about 3 grams. They are born helpless, with eyes closed, and with pink, wrinkled skin and white fur. At fourteen days their white fur begins to thicken, and size differentiation makes it easy to tell males from females. At 36 days old young weasels eyes open and they begin to be weaned and to eat foods brought back to the nest by their mother. They learn how to kill prey from the mother, and by 56 days they are able to kill prey on their own. Soon after they become independent.

How long do they live?

Many long-tailed weasels die before reaching one year old. However, once they have reached adulthood they may live for several years. The lifespan of long-tailed weasels in the wild is not well known.

  • Average lifespan
    Status: captivity
    8.8 years

How do they behave?

Long-tailed weasels are mainly solitary animals. Males and females do not associate, except during the mating season. One male's home range may overlap a few female home ranges, but the home ranges of adults of the same sex never overlap. Weasels exhibit very aggressive behavior towards intruders on their home ranges. Long-tailed weasels are quick, agile, and alert animals. They are excellent climbers and swimmers.

Long-tailed weasels hunt their prey by picking up on a scent or sound. They then follow the animal and make a quick attack. They kill their prey by a quick bite at the base of the skull.

While long-tailed weasels can be active during the day, they are more active at night. These weasels are also known to be noisy animals, but the noise is usually in response to some type of disturbance.

How do they communicate with each other?

Long-tailed weasels communicate among themselves with visual, sound, and scent cues. Females emit an attractive scent when they are ready to mate. Body language and sounds are used to communicate when weasels confront each other.

Long-tailed weasels have well-developed senses of sight, hearing, and smell, which allows them to be efficient and sensitive predators.

What do they eat?

The main prey of long-tailed weasels is small rodents like white-footed mice and meadow voles. Females, with smaller bodies, have better luck capturing small rodents because their bodies can fit inside rodent burrows. Males pursue larger animals, for example eastern cottontails. While mammals are the food of choice, long-tailed weasels eat a wide range of foods, including birds, crayfish, and snakes. In the summer their diet includes fruits and berries.

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates

What eats them and how do they avoid being eaten?

Long-tailed weasels are feisty and aggressive and will threaten animals much larger than themselves. They may be preyed upon by larger animals, such as large owls, coyotes, or large snakes, such as eastern massasauga rattlesnakes. They are especially vulnerable to predation as young.

What roles do they have in the ecosystem?

Long-tailed weasels help to control populations of rodents and rabbits.

Do they cause problems?

Long-tailed weasels have been know to raid captive poultry flocks. They are efficient predators and, like other members of their family, will kill and store as many prey as they can find. As a result they may kill entire flocks in a single night.

How do they interact with us?

Long-tailed weasel pelts are taken by trappers, but there is little demand for them. Long-tailed weasels are excellent at controlling mouse and rat populations, so are beneficial to farmers because they eliminate these pests.

  • Ways that people benefit from these animals:
  • body parts are source of valuable material
  • controls pest population

Are they endangered?

Long-tailed weasels are abundant and widespread. They do well in a variety of habitats and are not currently threatened.


Toni Lynn Newell (author), University of Michigan-Ann Arbor.


Baker, R.H. 1983. Michigan Mammals. Michigan State University Press. United States of America.

"Animal Life Histories Database" (On-line).

Ruff, S., D. Wilson. 1999. The Smithsonian Book of North American Mammals. Washington [D.C.]: Smithsonian Institution Press in association with the American Society of Mammalogists.

University of Michigan Museum of ZoologyNational Science Foundation

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Newell, T. 2002. "Mustela frenata" (On-line), Animal Diversity Web. Accessed May 18, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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