Beavers use their large dorsally
flattened, scale-covered tail to maneuver in water.
Slapping the tail on the water surface is used as a
signal of alarm. Beaver also slap their tails
during periods of play. Split nail on the
second hind toe is used for grooming. Incisors
are large and continually growing. Fur is rich
brown with black to reddish guard hairs.
Underfur is soft and extremely dense with excellent
insulating qualities. Both sexes have a pair
of anal glands and castor sacs located ventrally.
Beavers emit anal gland secretions year round.
Total length: 34
to 40 inches. Weight: 30 to
60 pounds and sometimes heavier.
Occupies a wide variety of habitats in North
America. Water and associated woody vegetation
are the most essential components of beaver habitat.
Ideal beaver living sites include ponds, lakes,
streams, and rivers.
Beavers are strict herbivores. Beavers eat a
variety of woody and herbaceous species.
Willows, mountain alder, and aspen are important
foods. Will also consume herbaceous vegetation
during summer. Much of the woody vegetation
beavers cut is not used for food. Caches woody
vegetation near shore for winter food.
Life History: Builds stick
and mud dams across streams. Mostly nocturnal.
May build large conical houses at the edge of a lake
or burrow into the bank for a den along rivers.
Beaver life is based on a family unit consisting of
a pair of adults, yearlings, and kits. Breeds
form January through March. 2 to 4 young are
born after a 105 to 107 day gestation period.
One litter per year is produced. Two-year-olds
are eventually driven from or leave the parental
River otter - tail covered with fur. Muskrat -
smaller, tail slender.
The beaver is the largest North
American rodent. A common furbearer, the beaver
inhabits waterways of every North American state and
Canadian Province. A unique paddle shaped tail
distinguishes the species and self-sharpening teeth
allow beavers to mow down sizable trees. Beaver
often alter the landscape with the construction of
dams, canals and lodges. Beaver are territorial as
long as the habitat will support family groups
called "colonies". Beaver are powerful animals both
on land and in the water.
to grow in size throughout life, and weights in excess
of 60 or 70 pounds do occur when foods are abundant and
accessible during the entire year. Unlike many other
species, females are as large as males of the same age,
and they sometimes are larger. A paddle shaped, leathery
tail, positively identifies the species. An adult's tail
is usually about 10 inches long, and 5 or 6 inches wide,
with a thickness of 1/2 inch in the middle.
The hind feet of beaver are fully
webbed, and large. These feet often measure 6 inches in
length, and the spread of the toes is equal to or
greater than the length as the beaver swims. Five toes
with strong nails are found on the hind feet, including
unique split toenail on one toe which serves the beaver
as a comb for grooming. The front feet seem small in
contrast to the hind feet. These feet measure 2 1/2 to 3
inches in length and are not webbed at all. Beaver
normally swim with their front feet held against their
chest, and the large webbed hind feet provide the
propulsion with the tail acting as a rudder.
Guard hairs in beaver fur are 2
inches in length, overlaying a soft and dense underfur
about an inch deep. Colors vary from section to section,
and from blonde colors to nearly black. Both male and
female beaver have large glands, called castors, beneath
the skin on the lower bellies. These glands produce an
oil which the beaver combs into its fur to waterproof
it. This oil is also deposited by the beaver at selected
locations as territorial markers or mating attractants
in the spring of the year.
Beaver have transparent eyelids
which cover the eyes as the beaver submerges, enabling
the beaver to see well when submerged as the eyeball is
protected from abrasive particles suspended in the
water. The ears and nose of a beaver have valves that
close as a beaver submerges, preventing the entry of
water. Two upper and two lower incisor teeth dominate
the front of a beaver's mouth. The upper incisors
overlap the lower incisors, and friction from chewing
causes the teeth to self-sharpen to chisel sharpness.
Similar to birds and reptiles, beaver
have a single lower body opening, known as a cloaca.
This single opening serves the urinary and bowel tracts,
the secreted oil from the castor glands, and covers the
reproductive organs of both males and females.
usually live in family units consisting of the older
mated pairs, young from the previous year, and young
from the current season called kits. Breeding season
takes place in late January or February in most states.
Young from the previous year are about 22 months of age
at this time and they are evicted from the colony to
relocate and seek mates of their own. The gestation
period of beaver is 107 days and the adult male and kits
usually take up a temporary residence in a bank den
while the new litter is being born in April, May or
June. The birthing process may take several days, and 3
to 5 kits are a typical litter size. Beaver kits are
fully furred when born, their eyes are open, and the
incisor teeth are visable. Newborn beaver kits take to
the water easily, and they might be swimming before they
are one day old. Most adult beaver are monogamous, and
stay with their mate throughout life.
Beaver require deep
water for protection from their enemies, and they alter
the landscape a great deal with dam building and
flooding. Dams can be hundreds of feet in length, and
vary in height from only a few feet to 7 or 8 feet, and
even higher at times.
Permanent lodges are often
constructed by piling layer after layer of sticks into a
large conical form above the waterline. Two or more
underwater tunnels are then chewed up into the pile, and
an inner chamber hollowed out to serve as a living
quarters. Finally the outside of the lodge is plastered
with mud and rocks, except for the peak, which is left
porous enough to allow an air exchange to the inner
chamber. There are two levels to the chamber. One level
is near the waterline near the "plunge holes", where the
beaver shed water before climbing to the higher resting
or nesting areas.
In areas prone to flooding, or where
strong currents may be present, beaver usually construct
bank dens by digging tunnels from underwater up into
banks. Bank dens often have two or more submerged
entrances. Many times the beaver will construct a pile
of sticks over the tops of the underground living
chambers. These piles of sticks are sometimes called
Shallow pockets are sometimes dug
into banks near the waterline and these are known as
"feed pockets". In northern areas, beaver construct
"feed piles" by submerging large amounts of small trees
and limbs to serve as a food source after ice prevents
the beaver from activity above the ice. These feed piles
are usually constructed close to the den as a
convenience to the kit beaver, who do not normally
travel far from the den itself.
At times, solitary beaver will be
found living alone. These beaver are known as
"bachelors", whether they are male or female.
Adult beaver mark out their
territories in early spring by dragging up mud and
debris from the bottom and depositing the debris in
mounds along the shores, where they also deposit oil
from their castor glands. These "castor mounds" often
leave a reddish stain on the bank, and the odors are
powerful enough for a human to easily detect.
Beaver are very territorial, and
territories seldom overlap. Generations of beaver may
continuously inhabit a choice area, even building canals
to help float food from inland cutting sites. If and
when food supplies are exhausted, they do relocate to
better area. Once beaver have determined to claim a
territory, they are very difficult to dissuade. If the
activities of the beaver flood roads or damage property,
the beaver usually have to be removed to prevent
Although beaver normally submerge for
3 or 4 minutes at a time, they are quite capable of
holding their breath for 12 to 15 minutes. They exhale a
little in spurts as they swim or work under water, and a
large beaver is quite capable of traveling nearly 1/2
mile under the surface before it must surface for more
Migrations of beaver usually occur
with the breaking up of ice in late winter or early
spring as the 22 or 23 months old beaver are expelled
just prior to birthing time for the new litter. These
beaver may chose to go up or downstream. Although these
beaver are capable of reproducing, they usually do not
until the next season, after a mate and a new territory
have been established. Most new colonies are established
within a few miles of the home colony.
Beaver are primarily vegetarians
although an occasional beaver may eat a dead fish.
Preferred foods include the bark of aspen, willow,
cottonwood, and dogwood, and many other varieties of
trees and shrubs. In early spring, beaver will often eat
bark and twigs of evergreens. In season, beaver will
also eat water lilies, leaves, grasses, roots, and a
variety of crops including corn, wheat, oats, carrots,
potatoes, apples, clovers, and alfalfa.
alter the habitat a great deal with the building of
dams, and the resulting flooding of lowlands. The deeper
water behind dams creates a better habitat for muskrats,
and a variety of other wildlife species such as fish and
waterfowl. Mink and otter hunt regularly around beaver
dams. These locations provide suitable denning sites as
well for these furbearers.
Dam building on trout streams can
have an adverse effect on trout survival by slowing the
water and allowing it to warm to temperatures higher
than the trout can tolerate. Dams also serve as barriers
to migrating trout and salmon. At times, beaver cause
significant amount of property damage by cutting trees,
and flooding large areas also killing the timber.
Culvert plugging is common, and often causes roads to
flood and to wash out.
Beaver are also host to an internal
parasite, giardiasis. Water reservoirs inhabited by
beaver can and do become contaminated by the giardiasis
cysts, which are too small to be filtered out of the
drinking water. These cysts hatch in the small
intestines of people who drink the contaminated water
resulting in diarrhea, nausea, and stomach aches.
Serious beaver predators include
mountain lions, wolves, lynx and bobcats. At times, a
bear can and will kill mature beaver. Juvenile beaver
are vulnerable to coyotes, eagles, and large owls as
well. Tularemia can be a devastating disease in beaver,
wiping out entire populations when conditions are good
for disease transmissions. Tularemia infects livers, and
is usually fatal to beaver of all ages.
A beaver is considered to be old at
12 year of age.
Best Management Practices
Special Regulations Note
STATEWIDE SEASON DATES:
Trapping Districts 1, 2 and 3: November 1 - April 15 of
the following year. Trapping Districts 4, 5, 6 and 7:
September 1 - May 31 of the following year, except State
Wildlife Management Areas and specific closures (See
Beaver that have been legally
trapped can be dispatched with a firearm.
Owners and lessees of property
being damaged by beaver may request a free permit to
remove beaver under provisions of state law between
April 16 - May 31 and Sept. 1 - Oct. 31. A landowner may
remove damaging beaver without a permit between June 1 -
Aug. 31. Please contact your local game warden for
further information and to request a damage control
A person participating in a
beaver damage complaint must have in their possession
the damage permit issued to the landowner (or a copy
thereof) during control activities. Damaging beaver may
be removed by trapping or shooting.
Closures - All
areas closed to beaver trapping are also closed to otter
Trail Creek and Trapper Creek drainages and Canyon Creek
upstream from the National Forest boundary.
Broadwater County: Those portions of Dry Creek, Confederate Gulch,
White's Gulch, Avalanche Gulch, Eagle Creek, Crow Creek,
Jenkins Creek on public land.
Deer Lodge County:
The entire Dry Cottonwood Creek drainage.
That portion of the Gallatin River and all of its
tributaries above the Gallatin River Bridge at the Squaw
Creek Ranger Station.
Gallatin and Park
Counties: That portion of the Yellowstone River
and all of its tributaries inside the Gallatin National
Forest boundary above the Yellowstone River Bridge on
Interstate Highway 90 at Livingston.
The entire Smart Creek, Wyman Creek, Swamp Gulch Creek,
and Sand Basin Creek drainages.
Lewis and Clark County:
The Blackfoot River upstream from the mouth of Bartlett
Creek including the entire Bartlett Creek drainage.
The entire Cedar Creek, Big Creek and Flatrock Creek
Missoula and Mineral
Counties Missoula County: Nine Mile Creek
drainage above Pine Creek.
The entire Pikes Peak drainage.
Sweet Grass County:
That portion of the East Boulder River and all its
tributaries from the Gallatin National Forest boundary
upstream to the headwaters of the East Boulder River.
Sweet Grass and Park
Counties: That portion of the Main Boulder
River and all its tributaries from the mouth of Falls
Creek upstream to the headwaters of the Main Boulder
The entire Teton drainage including all tributaries of
the South, Middle, West and North Forks of the Teton
River, downstream to the National Forest boundary.