The long-tailed weasel belongs to the Mustelid family, a group of mammals
known for their long bodies, short legs, and strong scent glands. The Latin
name is Mustela frenata refers to a bridle-like mask that is characteristic
Long-tailed weasels range across much of the United States, southwestern
Canada, and as far south as northern South
The long-tailed weasel is an aggressive carnivore, preying primarily
on mice, but also attacking animals much larger than
itself. Prey species include rabbits, chipmunks, shrews, rats, snakes, frogs, and birds, especially poultry. Weasels have even
been know to attack humans when being handled or when cornered. Not only is this species of weasel aggressive, but it
displays great agility and determination. In order to capture a squirrel, weasels have been known to climb 20 feet (6 m) up a
The weasel is prone to violent killing sprees. Weasels are notorious
for killing entire coops of chickens. The killing instinct
in the weasel is thought to be brought on by the smell of blood. Nothing that is injured and in its vicinity is safe from attack.
Siblings and even their own young can be killed and eaten. It is a common misconception that weasels will suck the blood
out of its victims. This fabled ability stems from the fact that weasels being seen with blood on their snout after they have
The long and slender body of the weasel allows it to move, almost flow,
over terrain. This body design makes it an effective
predator, able to follow its prey into the narrow tunnels of its den. Sometimes the weasel takes over the den of its prey and
will line the den with the fur of its victim. Long-tailed weasels can swim and climb quite effectively, but not with the
proficiency of its cousins the ermine and the fisher. Because of its slender body style, the weasel has a high metabolic rate.
In winter months it will use almost half of the food that it eats to maintain body heat. Weasels at rest will coil up with the
head to tail in the shape of a circle in order to conserve heat.
Female long-tailed weasels reach sexual maturity at 3 to 4 months of
age, while males usually don't reach maturity until their
second year. Weasels may drag their rumps during mating season. This is thought to be a way of leaving scent trails for
members of the opposite sex. Males also use this scent to declare their territory to other males. Long-tailed weasels usually
breed in July or August and show the ability to delay the implantation of the embryo into the uterus for about 7 months after
fertilization. This delay is thought to be a adaptation to giving birth when conditions are at their most favorable. Litters, from
1 to 10 pups, are born in underground nests that are lined with rabbit or rodent fur. The young are born without fur and are
essentially blind. The nest is part of an elaborate underground den that has several branches, some serving as latrines and
others as food storage areas. The pups do not remain with the mother long. At 7 to 8 weeks, the male pups are already larger
than their mother and the young leave the den not long after.
Weasels do not pose a serious threat to humans other than threatening
the poultry industry. Weasels are in fact a benefit in
that they destroy much of the rodent population that harms crops
Weasels are not considered an endangered species since they are found
throughout the North American continent. The main
threats to weasels are often predators such as the gray fox, red fox, coyotes, hawks, large snakes and owls. Man is the
weasel's greatest enemy as weasels are taken for their pelts, even though the fur itself is not of great value.
Canines - the eye teeth found next to the incisors.
Carnivore - those animals that primarily eat meat.
Endemic - known only from a particular locality.
Subspecies - is a population of a species that is physically or behaviorly different from other populations of the species but
still capable of interbreeding with them.
Terrestrial - living on land.
Forsyth, Adrian, 1985. Mammals of the American North. Camden House Publishing
Jones, J. Knox, et al, 1983. Mammals of the Northern Great Plains. University of Nebraska Press. Lincoln, NE.
Nowak, Ronald M., 1991. Walkers Mammals of the World. Johns Hopkins University Press, Baltimore, MD.
Grzimek, H.C. Bernard, 1975. Grzimek's Animal Life Encyclopedia, Vol 12 (Mammals III). Van Nostrand and Reinhold
Company New York.
Whitaker, John O., 1980. The Audubon Society Field Guide to North American Mammals. Alfred A. Knopf Inc.
Casey Dreis, biology student, Northern State University, Aberdeen, SD. 1997.
Kathy Colavitti, independent artist, Green Bay, WI.
Doug Bucklund, Resource Biologist, S.D. Department fo Game, Fish, and Parks, Pierre, SD.
Publication of the Long-tailed Weasel fact sheet was funded by
the South Dakota Department of Game, Fish and Parks,
Division of Wildlife, Pierre, SD.