Montana Trappers Association

Working Today For a Tomorrow in Trapping.
Furbearers Are A Natural Renewable Resource.

Long Tailed Weasel


Weasel Family

Classification: Non-game Wildlife Species

Mustela frenata

Order: Carnivora
Family: Mustelidae

Status: Fur of some value, unprotected predator.


Identifying Characteristics: Largest and most widely distributed of the three North 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 underparts, 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.  Weights: 3 to 12 ounces.


Habitat: 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.


Food Habits: 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.


Life History: 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.  Mates during summer; 205 to 337 day gestation; delayed implantation; young born during April; litter size 4 to 9.


Similar Species: Short-tail weasel - white line down inside of leg, smaller.  Least weasel - no black tip on tail, smaller.  Mink - nearly uniform dark brown.  Marten - heavier, much larger.


The long-tailed weasel, which is the largest of the three weasels found in Montana and varies from 13 to 18 inches in length, including a 6 1/2 inch tail.  It is the long tail which gives it its name. They are about 2 to 3 1/2 inches high and weigh up to 12 ounces.


It has a long, slender, muscular body with short legs. The head is small, with beady eyes, small ears and a pointed nose. They move with quick movements and a graceful, bounding gait. All three weasels change color with the seasons, and there is no color difference between the sexes. All the senses are well developed in the weasel.


The long tailed weasel is much the same in color as the short tailed weasel except that, in some areas, it does not become white in winter. The feet are dark brown in summer whereas the short tailed weasel has pale yellowish feet in summer. The tail has a black tip throughout the year. The molting pattern is different than in short tailed weasels, starting on the back in spring and causing a brindled appearance to the facial markings.


Life Cycle
The long-tailed weasel females mature at 3 to 4 months and males mature at about one year. The breeding season is in July. There is a period of delayed implantation with a gestation period of 9 to 10 months. The period of active pregnancy is 23 to 17 days.


Litter sizes varies from four to thirteen, with an average of six to eight. The young are born in April or May in nests constructed in underground dens or hay piles. Mouse nests and burrows are often used and heavily lined with fine grass and mouse fur. The male begins to bring food to the den about 1 month after the young are born. The young are weaned at the end of 5 weeks and are able to hunt for themselves by 7 or 8 weeks of age. The family stays together until late summer and then disperses. The life expectancy of weasels is short, probably less than a year, although they are capable of living as long as 6 years.


Weasels prey on small rodents such as mice, rats, voles, hares, rabbits, and chipmunks. They also take shrews, birds, birds eggs, frogs, bats, insects, earthworms and may occasionally kill domestic chickens.


The weasel hunts by tirelessly and persistently investigating every small hole, crevice, bush or rock pile it encounters. They will track prey by following their scent trails and generally attack prey by ambushing and pouncing on it. They are very quick and kill by piercing the base of the skull with their teeth. The weasel frequently kills more than it can eat and often caches leftover food. The weasel can consume up to one third of its own weight in a 24 hour period.

Weasels are curious, alert and bold. They are persistent hunters who seldom remain long in their dens and may be abroad hunting at any hour, although they are usually most active at night. Weasels are active year round. Weasels occasionally hunt in pairs but, for the most part, are solitary except during breeding and rearing season. They are good swimmers and can also climb trees. All species emit a strong musk odor when alarmed, and the weasel may stamp its feet when annoyed. Weasels may mark their trails with droppings. Home ranges very from 30 to 400 acres.


Weasel populations often cycle with mouse populations. Several parasites can infect weasels, such as guinea worm and kidney worms. These probably have little impact on the population.


Weasels are subject to predation from hawks, owls, foxes, coyotes, dogs, cats and man.


In agricultural areas, weasels are more common due to the practice of storing grain which provides ideal conditions for mice.


Weasels prefer woodlands or open country with hedgerows, thickets or fence rows. They are usually found near water but are not semi-aquatic as is the mink. They frequent stone piles, brush heaps, wood piles, hay stacks, log piles and old abandoned buildings.


The long-tailed weasel is found in almost all land habitats near water.  It has the broadest ecological and geographical range of the North American weasel. It avoids dense forests.


The dens of weasels are shallow chambers about 6 inches underground with two to three entrances and are lined with mouse fur and grass.


Economic Value
The fur of the long-tailed weasel commands a higher price because it is so much larger.


Weasels play an important role in helping to control rodent populations.

Did You Know?

Jim Bridger (1804-1881). Trapper, scout, mountain man. One of first white men to see the future Yellowstone Park and Great Salt Lake, which he believed to be an arm of the Pacific Ocean. Became partner of Rocky Mountain Fur Company in 1830 and established Fort Bridger in Wyoming Territory in 1842. Laid out routes for the Central Overland Stage and Pike's Peak Express Company. Returned to Missouri in 1867 where died on his farm on July 17, 1881.


Rendezvous were held on a yearly basis at various locations until 1840, mainly in Wyoming, but Pierre's Hole in Idaho and Bear Lake in northwest Utah were favorite sites as well.


Fort Manuel Lisa was established in 1807 by Manuel Lisa at the mouth of the Big Horn River near Hysham. This was the first permanent settlement in Montana and was occupied until 1811.


John Jacob Astor was the first prominent member of the Astor family and the first multi-millionaire in the US. He amassed his wealth through fur-trading, opium smuggling, and New York City real estate. Famed patron of the arts. At the time of his death, he was the wealthiest person in the US.


In 1919, the Hudson’s Bay Company was approaching its 250th year in business. What began in a coffee house in London, in 1670, had now grown to become the undisputed leader of the international fur trade.


The desire for beaver fur hats in European men’s fashions dates back centuries and spurred the development of the 17th century North American fur trade. Beaver fur was the most prized of the fur trade because of its water repellant qualities. Encouraged by European trade goods, natives hunted beaver to extinction in some areas.