Distribution & Abundance |
Habitat | Habits
| Foods |
Reproduction | Conservation
-- Image courtesy of James F. Parnellę --
species of weasels live in Illinois--the long-tailed weasel and the least
weasel. The long-tailed weasel is two to three times larger than the least weasel. Both
have long, slender bodies, short legs, and a broad, slightly flattened head
that's barely larger around than the neck.
Male long-tailed weasels are larger (13 to 16 inches in length; 6 to 16 ounces) than
females (11 to 14 inches in length; 3 to 9 ounces). The tail is nearly half as long as
the head and body combined and has a distinctive black tip.
The least weasel is the smallest living carnivore in Illinois. Males are up to
10 inches in length (including the tail) and weigh 2.1 to 3.2 ounces. Females are
up to 9 inches in length and weigh 1.2 to 2.5 ounces. The tail is less than
one-fourth of the length of the head and body combined.
Both species have a summer coat that's reddish-brown or tan except for a
yellowish-white belly. Weasels begin shedding their summer coats during early
fall and replace them with winter coats that tend to be lighter in color. In
parts of northern Illinois, the winter coat is nearly all white, helping them to
blend in with a snowy background and avoid detection by predators like hawks and
owls. Further south (where snow cover is uncommon), the winter coat can have
patches of brown and white or remain mostly brown like the summer coat. Weasels
molt again in the spring, replacing their winter coats with darker summer
Distribution & Abundance
Long-tailed weasels are found throughout Illinois. Least weasels are found
only in the northern half of the state. Populations of both species tend to be
scattered, occurring mainly in areas with good habitat and high numbers of
Long-tailed weasels can be found in a wide variety of habitats, but prefer
forests, woodlands, thickets and brushy fence rows. Least weasels tend to be
found in more open areas like meadows, grasslands and river bottoms. Both
species do best in areas with access to water and high rodent populations. Their
dens are usually found in rock piles, junk heaps, abandoned buildings and
burrows dug by mice, ground squirrels, moles or chipmunks. They sometimes line
their nest chambers with grass or fur and feathers from their prey.
Both species make a wide range of sounds. A loud, harsh chirp or a screech
can be heard when a weasel is disturbed or ready to attack. A low trill often
signals a friendly meeting between a male and a female. A trill also helps a
female to call her young. Baby weasels make high-pitched squeaks. At about four
weeks of age, their squeaks get lower-pitched and raspier, eventually reaching a
chirp similar to the adults'.
Weasels can be seen during daytime, but are most active at night. The size of
the area they live in depends on the amount of food found there. For example,
the home range of a least weasel might be as small as 1.7 to 2.5 acres where food
is abundant or as large as 37 to 65 acres where food is scarce. The home ranges of
long-tailed weasels can vary from 25 to 400 acres depending on food supplies.
Both species follow regular hunting routes, covering only parts of their home
ranges during a single night. Hunting routes usually start and end at a den.
Total distances covered in a night can be less than a tenth of a mile up to 3
1/2 miles for long-tailed weasels. Males travel farther than females. Not much
is known about the daily movements of least weasels. They probably travel much
shorter distances than long-tailed weasels.
Small prey like mice are killed with a few quick bites to the back of the
neck--where the neck joins the skull. Weasels also stalk larger prey, trying to
take them by surprise. If the stalk is successful, the weasel rushes in and
grasps onto the prey animal with its front and hind feet. During the struggle
that follows, the weasel tries to position itself on the animal's back for a
series of bites to the base of the skull. Prey found in tunnels are attacked
head-on and killed by a crushing bite to the windpipe.
Weasels bound or lope with the back arched and tail held straight out or
slightly higher than the plane of the back. They swim well and climb trees
easily. Their small girth (1 to 1 1/2 inches) lets them slip through small
knotholes, crevices and tunnels when chasing prey.
Long-tailed weasels eat mice, rats, voles, squirrels, chipmunks, shrews,
moles and rabbits. Less common foods include birds, bird eggs, snakes, frogs and
insects. Least weasels specialize in taking small prey such as mice and voles.
They do most of their hunting in tunnels made by these rodents.
Long-tailed weasels have only one litter per year. They mate in July or August.
The fertilized eggs develop for eight days, then enter a dormant period. About 7 1/2
months later, the eggs attach to the wall of the uterus and resume development.
The young are born 23 to 27 days later, usually during April or May. Litter sizes
vary from one to nine and average four to five young. Young long-tailed weasels begin hunting
with their mother at 6 to 7 weeks and are ready to leave her at about 11 to 12 weeks.
Least weasels can breed year-round. They produce more young when rodent
numbers are high. For example, they might have one litter per year when food is
scarce and two or even three per year when prey is abundant. The gestation
period (pregnancy) is about 35 days long. There may be as few as one or as many
as ten young in a litter, but the average is four to five. The young develop quickly when
food is plentiful, reaching sexual maturity at 3 to 4 months. Under normal food
conditions, females reach sexual maturity at 4 months and males at about 8
Illinois allows a limited trapping season for weasels, but very few (usually
fewer than 20) are harvested each winter because populations are scattered and
few trappers attempt to catch them unless they're causing damage like killing
Few people manage habitat specifically for weasels. However, they benefit from
broader soil, water and wildlife conservation practices. Planting grass strips
along creeks, streams and rivers provides habitat for weasels and their prey
while reducing soil erosion and runoff from heavy rains. Woody fence rows
provide wildlife habitat and act as windbreaks that reduce soil erosion. Once
common in Illinois, many fence rows have disappeared because large fields with
few obstacles are more efficient for modern farm equipment. Some have been
removed because trees shade and wick away moisture from nearby crops, causing
lower yields. In these cases, a root plow can be used to trim tree roots next
to fence row and improve crop yields. Building brush or rock piles can provide denning areas for weasels and other wildlife.