Weasels are classified under the family name Mustelidae. The weasel family is large and diverse with about 70 species described
worldwide. Members of this family are found on all continents except Australia, Antarctica and the island of Madagascar.
Biologists used to classify skunks as members of the weasel family. However, recent genetic evidence (1997) has supported
reclassifying them in their own family (Mephitidae). Alberta's only representative of this family, the striped skunk, is
included here with the weasels. See:
The weasel family belongs to the Order Carnivora, the meat-eaters. With the exception of the northern river otter, all members
of the weasel family feed primarily on insects and small rodents. Their diet consists of whatever meat they can obtain and
may include birds and bird eggs.
Members of the weasel family are long-bodied, short-legged, agile predators who hunt persistently and attack prey up to
four times their size.
The lifestyle of weasels varies considerably, ranging from that of the river-dwelling otter and the prairie-dwelling badger
to the tree-dwelling marten.
Weasel jaws are short and well muscled, thus increasing their strength. The jaws are designed to minimize slippage of anything
in their grasp.
Another special characteristic of weasels is their anal glands which produce scent. Scent is used to mark the boundaries
of their territories and may also indicate their reproductive state.
Alberta's weasel representatives include the smallest of all living carnivores, the 70 gram (2.5 ounce) least weasel, as
well as the largest of the weasels, the wolverine, which may weigh 16 kilograms (35 pounds).
Male weasels are usually about one-third larger in size than females.
Food and the Food Chain
Weasels are usually active year-round and may hunt by day or night. In the past, weasels have been accused of killing more
prey than they could possibly eat, but research has shown they commonly cache excess food for later use.
Considering their fast-paced lifestyle, which may require weasels to eat the equivalent of one-third of their body weight
in meat each day, such food caches do not last long.
As predators, weasels play an important role in the animal community. They live off the annual surplus of animals they prey
upon. Generally, they capture those animals which are less fit to survive, usually the young, old, injured or sick.
Predators also tend to hunt the most abundant prey, turning to another prey species if the numbers of the first become scarce.
In this way, they seldom endanger the long-term welfare of the animal populations they prey upon.
The same agility and ferocity used in hunting is used for defence. Members of the weasel family have few natural enemies.
Wolverines have been known to bluff grizzly bear and cougar off their kills, and even the short-tailed weasel may turn on
a person if forced to defend itself.
In some members of the weasel family, mating occurs in the fall or early spring. In other weasel species, the female is
virtually pregnant throughout her life. Soon after she gives birth to a litter in spring, she will mate again.
The embryo begins to develop, then stops growing until late winter when development resumes. This phenomenon is called "delayed
implantation," which also occurs in bears in Alberta.
The benefits of such delayed embryo development are related to food availability and the energy demands of the seasons.
Mating and much of pregnancy occurs during the spring and summer months, when food is abundant and climatic conditions are
Weasel young, or kits, are born early in the year so they are fully grown before entering the harsh winter months.
Weasels and Biodiversity
Weasels are a vital and necessary component of Alberta's ecosystems. They are part of, and help maintain, the biodiversity
(the variety of species) in these systems, which in turn helps stabilize them.
People can be the greatest threat to their survival or, if we choose to manage them wisely, we can be their greatest benefactor.
Alberta's Weasel Species
The weasel species presented in this website include the following:
Updated: Jul 29, 2015