MANAGING BEAVER PROBLEMS IN KENTUCKY
Thomas G. Barnes
Historically, the beaver (Castor
canadensis) was North America's most important fur resource. During
the 1800s, the unrelenting pursuit and uncontrolled harvest of beavers
for their pelts led to extermination throughout much of the animal's range.
However, in the early 1900s the beaver received protection. Because of
this protection and resulting restoration efforts, including transplanting
beaver and changing land management practices, the beaver made a remarkable
comeback. Beaver numbers today are at, or exceed, their population levels
before the arrival of white settlers in North America.
Beavers sometimes cause problems or
become a nuisance when their feeding and dam-building activities conflict
with man. This publication provides information on the identification,
biology and natural history of beavers and how their feeding and dam-building
activities can be prevented or controlled.
The beaver, fairly common throughout
Kentucky, is North America's and Kentucky's largest rodent. It belongs
to the family Castoridae. Adult beavers weigh between 35 and 60 pounds,
with some reaching weights of 70 to 80 pounds. Adult beavers range in size
from 25 to 31 inches from the tip of their nose to the base of their paddle-shaped
tail. Beavers typically have large heads, indistinct necks, thick, stout
bodies and small ears and eyes.
Perhaps their most recognized feature
is a large, flat, hairless tail shaped like a paddle. This six- to eight-inch
wide and 10- to 12-inch long tail is used for support when the beaver is
on land and as a steering, swimming and communication device when it is
in the water.
Beavers are uniquely adapted for life
in the water. They have short, stout legs specialized for swimming and
working. The large, fully webbed hind feet are adapted for swimming, whereas
the small front feet are very dexterous, nimble and not webbed. Beavers
use their front feet for digging as well as for holding and manipulating
small twigs while they peel the bark off with their teeth.
Other adaptations for an aquatic lifestyle
include ears and nostrils with valves that close when the beaver is submerged,
eyes that are set high on the head to allow the beaver to see above water
when swimming and lips located behind the front teeth that close when a
beaver is submerged, allowing it to use its teeth under water.
Like many other rodent species, beavers
have a pair of continually growing, large, orange front teeth (incisors).
The beaver must keep the incisors worn back by using them daily.
Beaver fur, which was highly sought
after and is somewhat in demand today, is comprised of a gray, soft, dense
undercoat protected by long, coarse reddish-brown guard hairs. Color can
vary from blond to almost pure black. Beavers carefully groom and comb
their fur with oil from various glands, using the second claw on each hind
foot, which is split lengthwise. Grooming with oil helps keep the beaver
from becoming wet at the skin's surface. The beaver also has a pair of
scent glands called "castor sacs." These glands produce a substance called
castoreum which is used as a chemical signal to other beavers. It is almost
impossible to tell the difference between male and female beavers unless
the female is lactating and has swollen mammary glands.
Beaver Facts and Biology
The beaver is one of a few mammals,
other than man, capable of modifying its habitat to suit its needs. When
beavers move into an area, they quickly begin building dams to modify the
habitat more to their liking. Once the dam has been built from surrounding
timber, the subsequent flooding causes growing timber to die, and other
aquatic vegetation begins growing. Often, the new plants growing around
the edge of the pond (willows, sweetgum and blackgum) are preferred beaver
foods. Thus, good beaver habitat can be almost anywhere there is a year-round
source of water. Appropriate habitat can include streams, rivers, ponds,
lakes, large reservoirs, swamps, wetlands and drainage ditches.
Beavers are incredible, highly skilled
engineers. They build dams on fast- and slow-moving streams to create a
pond with a stable water level. They show unusual skill in selecting dam
locations. The dam is usually constructed of sticks, mud and stones and
provides the water impoundment for the main lodge.
Home to a beaver is its lodge or bank
den, depending on the situation. Lodges are dome-shaped structures built
of sticks and mud with a large interior chamber above the water line. Lodges
vary in size from 6 to 40 feet, depending on the number of beavers in the
colony. Beavers sometimes dig burrows into the banks of ponds, rivers and
drainage ditches instead of building a lodge. All lodge and bank den entrances,
normally two or more, are located underwater.
Beavers live in family units called
colonies, which range in size from two to eight beavers (the average colony
size is five to six). A colony consists of the adult pair, the current
year's offspring (kits), the previous year's offspring (yearlings) and
occasionally a 21/2 year old offspring. Beavers are highly territorial
animals, and they actively defend the colony's territory against outsiders
by using scent marking. When beavers become sexually mature around age
two, they leave their home colony to form a colony of their own.
Beavers mate in January or February.
Two to four one-pound kits (similar in appearance to the parents) are born
in March or April. Kits grow rapidly, nursing for approximately 60 days,
and by six months of age they weigh between eight and ten pounds. Beavers
have a relatively long life span for a wild animal. Most beavers do not
live beyond ten years of age, although some may live 20 years or more.
"Busy as a beaver" appropriately describes
beaver behavior. Primarily a nocturnal animal, beavers are active for approximately
12 hours each night, feeding and working on the dam. It is not uncommon
to see beavers during daylight hours, particularly in large reservoirs.
Most daily movements are centered around the pond and lodge. Individual
movements vary greatly.
The female parent in the colony is
relatively sedentary, occupied with caring for young during the spring
and summer. Two-year-old beavers may travel five to six miles in search
of appropriate habitat conditions necessary for establishing a new territory.
Other travels by individual beavers include wanderings by yearlings and
adults who have lost their mates.
Beavers feed on the cambium layer (just
under the bark) of woody plants and a variety of aquatic and upland vegetation.
Preferred woody foods include willow, birch, maple, alder, cherry and poplar,
although they can and will feed on the leaves, twigs and bark of most species
of woody plants. During the summer beavers will also eat water lilies,
pond weeds and cattails. Sometimes beavers will travel substantial distances
from the pond or stream to get to corn or soybean fields, where they cut
the plant off at ground level and drag it back to the water. What they
do not eat, they use for construction material in dams and lodges.
Benefits of Beavers
Beavers are generally considered beneficial
in situations where they do not compete with people for the use of the
land, water or timber. Harvest of beaver pelts may be a source of income.
While fur prices vary from year to year based on fashion trends, a recent
survey done by the Kentucky Department of Fish and Wildlife Resources reported
that more than 1,500 beaver pelts, valued at more than $20,000, were sold
during the 1986-87 trapping season. Beaver ponds also attract a wide variety
of other furbearing animals including mink, muskrat and raccoon. The value
of these pelts, based on the same survey, was in excess of $1.4 million.
The unique dam- and pond-building attributes
of beavers create favorable habitat for a variety of wildlife species,
including fish, ducks, shorebirds, amphibians and reptiles. The variety
of wildlife attracted to these ponds can be used for recreational, scientific
or aesthetic purposes.
Ponds created in beaver dams help stabilize
water tables, reduce rapid runoff from heavy rainfall and reduce soil erosion
by depositing silt in the pools. Beaver castoreum is used in numerous trapper's
lures, perfumes and cosmetics. Finally, beaver meat is excellent table
fare if properly prepared.
Most beaver damage is relatively easy
to identify. Much of tiffs damage is associated with or is a result of
dam building, bank burrowing, tree cutting or flooding. Spring and fall
are the periods when landowners experience the most severe damage from
Damage in urban areas includes cutting
or girdling of ornamental and shade trees or shrubs. Because beavers are
rodents with large sharp incisors, damage to trees appears as clean, knife-like
cuts at a 45-degree angle.
In rural areas, beavers may dam drainage
ditches and small streams and plug drain pipes or culverts. This can lead
to localized flooding of roads, timber lands or agricultural cropland.
A hazard associated with beavers is
giardiasis, a disease caused by a protozoan (Giardia lamblia). This
pathogenic intestinal parasite can be carried by beavers and transmitted
to humans through the local water system. The extent of giardiasis is unknown
in Kentucky, although some beavers with the parasite have been found in
Prevention and Control of Beaver Problems
Beavers are classified as furbearing
animals in the state of Kentucky. An open trapping season is established
for the legal harvesting of these animals, and they are subject to all
applicable state laws and regulations. Consult the Kentucky Department
of Fish and Wildlife's trapping digest for more information on removal
of beavers during the legal trapping season.
If a beaver is damaging your property,
you can kill the animal at times other than the legal trapping season.
After the animal has been destroyed, you must contact your local conservation
officer for disposal of the carcass.
If the beaver pond has been in existence
for a considerable period of time (even if it is flooded cropland), the
area may be officially classified as a wetland. Under the provisions of
the 1985 Food Security Act, Conservation Reserve Provision, it may be illegal
to destroy the dam and drain the wetland. Contact the U.S. Army Corps of
Engineers in Louisville or your local Agricultural and Soil Conservation
Service, Soil Conservation Service or Kentucky Department of Fish and Wildlife
Resources office for an on-site visit and recommendation.
Nonlethal Prevention and Control
Individual high-value shade or ornamental
trees can be protected from beavers by wrapping them with 1/4- or 1/2-inch
hardware cloth to a height of four feet. Small areas around culverts, drains
and ponds in urban areas can be fenced using netwire with small mesh wire.
Another method of discouraging beavers
is to install a device to manipulate the water level of a pond. This can
be accomplished by installing a three-log drain (Figure 3) or wire mesh
culvert that the beavers cannot plug. Lowering the water level in the summer
encourages wild or planted foods to grow, providing excellent habitat and
food for waterfowl.
For more information on constructing
water control structures to discourage beavers and enhance waterfowl habitat,
contact a Kentucky Department of Fish and Wildlife Resources District biologist
or the Cooperative Extension Service.
One innovative way to discourage beavers
is the use of a high tensile electric fence (Figure 4). Stake a portable
battery or solar-powered charging unit some distance from a run (slide)
or a hole knocked into the dam. If you are placing the wire across a slide,
mow or trim the vegetation very close to the ground. Finally, string a
single strand of wire three inches above the ground or water's surface
so the beavers will strike it as they pass through the slide or attempt
to repair the hole in the dam. This electric shock acts to repel the animals;
if they are shocked enough, they will move to another area.
Daily tearing out dams and removing
dam construction materials with dynamite may cause a colony or individual
beaver to move. This is very dangerous and not recommended. Even if this
procedure is effective, the beavers may move into a new area and become
even more troublesome.
There are no chemical repellents or
toxicants (poisons) registered for controlling beavers in Kentucky. The
only control method that works well is trapping. The most effective trap
is a number 330 Conibear (instant-kill-type) trap. This trap is designed
to be placed underwater near a break in the dam, at the lodge entrance,
near a slide or on a beaver run (Figure 5a), (Figure 5b), (Figure 5c),
(Figure 5d).Trapping should be done by an experienced trapper because these
traps exert a tremendous pressure and impact when tripped. Therefore, appropriate
care must be taken when setting and placing the trap.
The Kentucky Department of Fish and
Wildlife Resources, #1 Game Farm Road, Frankfort, KY 40601 provides technical
guidance to landowners experiencing beaver problems. If the beaver problem
is large in scope or particularly severe, contact USDA-APHIS-ADC, 3231
Ruckriegel Parkway, Louisville, KY 40299 for assistance.
It is against the law in Kentucky to
destroy or harm a beaver lodge or den. Contact the Kentucky Department
of Fish and Wildlife Resources or USDA-APHIS-ADC in Louisville for technical
guidance before destroying dams.