Mustela frenatalong-tailed weasel

Geographic Range

The range of the long-tail weasel includes most of North America, extending from just north of the United States-Canadian border and south to Central America to northern South America (Baker, 1983). Long-tailed weasels have the largest distribution of any mustelid in the Western Hemisphere.


Long-tailed weasels are found in temperate and 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 in hollow logs, rock piles, and under barns. Sometimes instead of building a new nest, long-tailed weasels take over the burrow of one of their prey (Baker, 1983).

Physical Description

Long-tail weasels have a long slender body, similar to other weasels. On average, males are larger than females. These weasels have long, bushy tails that are about 50% of their total body length. Body length varies between 330 and 420 mm in males and 280 to 350 mm in females, tail length is from 132 to 294 mm in males, and 112 to 245 mm in females. Long-tailed weasels have a small, narrow head with long whiskers. They also have short legs. The 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. Twice a year these weasels shed their fur, once in the spring and again in the fall. This process is controlled by photoperiod. 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 (Baker, 1983).

  • 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


Mating for long-tailed weasels occurs in the mid-summer months. After copulation, implantation is delayed and the egg does not begin to develop until March, making the total gestation time around 280 days. Birth occurs from late April to early May, and the average size of the litter is six. At birth young weasels weigh about 3 grams. They are pink with wrinkled skin, and they have white fur. At fourteen days, the white hair begins to thicken, and size differentiation makes it easy to tell males from females. At 36 days young weasels are weaned and can eat food brought back to the nest by the mother. They learn how to kill prey from the mother and by 56 days old they are able to kill prey on their own. Females mate in their first summer, but males wait until the following spring (Baker, 1983).

  • Breeding interval
    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.


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


Long-tailed weasels are not social animals; the sexes live apart from each other except during the mating season. One male's home range may overlap several female home ranges, but home ranges of adults of the same sex never overlap. Weasels exhibit very aggressive behavior to intruders of their home ranges.

Long-tailed weasels are quick, agile, and alert animals. They are good climbers and swimmers.

Long-tailed weasels hunt their prey by picking up a scent or sound. They then follow the animal and make a quick attack. They kill their prey by a quick bite to 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 (Baker, 1983).

Communication and Perception

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.

Food Habits

Main prey are small rodents. Females, with smaller bodies, have better success in hunting small rodents because their bodies can fit inside the small rodent burrows. Males pursue larger animals, such as eastern cottontail rabbits. While mammals are the food of choice, these weasels eat a wide range of food, from birds to reptiles, and in the summer their diet includes fruits and berries (Baker, 1983).

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates


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.

Ecosystem Roles

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

Economic Importance for Humans: Positive

The pelts of long-tailed weasels were available in the fur trade but were not a popular commodity. Long-tailed weasels are good mousers and ratters, so farmers do not mind having weasels around their farms because they eliminate these pests (Baker, 1983).

  • Positive Impacts
  • body parts are source of valuable material
  • controls pest population

Economic Importance for Humans: Negative

Long-tailed weasels are known to raid poultry flocks (Baker, 1983).

Conservation Status

Long-tailed weasels are widespread and fairly common throughout their range.


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



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.


uses smells or other chemicals to communicate

delayed implantation

in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.

  1. active during the day, 2. lasting for one day.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


having more than one female as a mate at one time

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


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.