The woodchuck (Marmota
monax, Fig. 1), a member of the squirrel family, is
also known as the “ground hog” or “whistle pig.” It is
closely related to other species of North American
marmots. It is usually grizzled brownish gray, but white
(albino) and black (melanistic) individuals can
occasionally be found. The woodchuck’s compact, chunky
body is supported by short strong legs. Its forefeet
have long, curved claws that are well adapted for
digging burrows. Its tail is short, well furred, and
Both sexes are similar in
appearance, but the male is slightly larger, weighing an
average of 5 to 10 pounds (2.2 to 4.5 kg). The total
length of the head and body averages 16 to 20 inches (40
to 51 cm). The tail is usually 4 to 7 inches (10 to 18
cm) long. Like other rodents, woodchucks have white or
yellowish-white, chisel-like incisor teeth. Their eyes,
ears, and nose are located toward the top of the head,
which allows them to remain concealed in their burrows
while they check for danger over the rim or edge.
Although they are slow runners, woodchucks are alert and
scurry quickly to their dens when they sense danger.
throughout eastern and central Alaska, British Columbia,
and most of southern Canada. Their range in the United
States extends throughout the East, northern Idaho,
northeastern North Dakota, southeastern Nebraska,
eastern Kansas, and northeastern Oklahoma, as well as
south to Virginia and northern Alabama (Fig. 2).
In general, woodchucks
prefer open farmland and the surrounding wooded or
brushy areas adjacent to open land. Burrows commonly are
located in fields and pastures, along fence rows, stone
walls, roadsides, and near building foundations or the
bases of trees. Burrows are almost always found in or
near open, grassy meadows or fields. Woodchuck burrows
are distinguished by a large mound of excavated earth at
the main entrance. The main opening is approximately 10
to 12 inches (25 to 30 cm) in diameter. There are two or
more entrances to each burrow system. Some secondary
entrances are dug from below the ground and do not have
mounds of earth beside them. They are usually well
hidden and sometimes difficult to locate (Fig. 3).
During spring, active burrows can be located by the
freshly excavated earth at the main entrance. The burrow
system serves as home to the woodchuck for mating,
weaning young, hibernating in winter, and protection
Woodchucks prefer to feed
in the early morning and evening hours. They are strict
herbivores and feed on a variety of vegetables, grasses,
and legumes. Preferred foods include soybeans, beans,
peas, carrot tops, alfalfa, clover, and grasses.
General Biology, Reproduction, and Behavior
Woodchucks are primarily
active during daylight hours. When not feeding, they
sometimes bask in the sun during the warmest periods of
the day. They have been observed dozing on fence posts,
stone walls, large rocks, and fallen logs close to the
burrow entrance. Woodchucks are good climbers and
sometimes are seen in lower tree branches. Woodchucks
are among the few mammals that enter into true
hibernation. Hibernation generally starts in late fall,
near the end of October or early November, but varies
with latitude. It continues until late February and
March. In northern latitudes, torpor can start earlier
and end later. Males usually come out of hibernation
before females and subadults. Males may travel long
distances, and occasionally at night, in search of a
mate. Woodchucks breed in March and April. A single
litter of 2 to 6 (usually 4) young is produced each
season after a gestation period of about 32 days. The
young are born blind and hairless. They are weaned by
late June or early July, and soon after strike out on
their own. They frequently occupy abandoned dens or
burrows. The numerous new burrows that appear during
late summer are generally dug Fig. 3. Burrow system of
the woodchuck. Side entrance Nest chamber Main entrance
Fig. 2. Range of the woodchuck in North America. B-185
by older woodchucks. The life span of a woodchuck is
about 3 to 6 years. Woodchucks usually range only 50 to
150 feet (15 to 30 m) from their den during the daytime.
This distance may vary, however, during the mating
season or based on the availability of food. Woodchucks
maintain sanitary den sites and burrow systems,
replacing nest materials frequently. A burrow and den
system is often used for several seasons. The tunnel
system is irregular and may be extensive in size.
Burrows may be as deep as 5 feet (1.5 m) and range from
8 to 66 feet (2.4 to 19.8 m) in total length (Fig. 3).
Old burrows not in use by woodchucks provide cover for
rabbits, weasels, and other wildlife. When startled, a
woodchuck may emit a shrill whistle or alarm, preceded
by a low, abrupt “phew.” This is followed by a low,
rapid warble that sounds like “tchuck, tchuck.” The call
is usually made when the animal is startled at the
entrance of the burrow. The primary predators of
woodchucks include hawks, owls, foxes, coyotes, bobcats,
weasels, dogs, and humans. Many woodchucks are killed on
roads by automobiles.
On occasion, the
woodchuck’s feeding and burrowing habits conflict with
human interests. Damage often occurs on farms, in home
gardens, orchards, nurseries, around buildings, and
sometimes around dikes. Damage to crops such as alfalfa,
soybeans, beans, squash, and peas can be costly and
extensive. Fruit trees and ornamental shrubs are damaged
by woodchucks as they gnaw or claw woody vegetation.
Gnawing on underground power cables has caused
electrical outages. Damage to rubber hoses in vehicles,
such as those used for vacuum and fuel lines, has also
been documented. Mounds of earth from the excavated
burrow systems and holes formed at burrow entrances
present a hazard to farm equipment, horses, and riders.
On occasion, burrowing can weaken dikes and foundations.
Legal Status In most states, woodchucks are considered
game animals. There is usually no bag limit or closed
season. In damage situations, woodchucks are usually not
protected. The status may vary from state to state,
depending on the control technique to be employed.
Consult with your state wildlife department,
USDA-APHIS-Animal Damage Control representative, or
extension agent before shooting and/or trapping problem
Prevention and Control Methods
Fencing can help reduce
woodchuck damage. Woodchucks, however, are good climbers
and can easily scale wire fences if precautions are not
taken. Fences should be at least 3 feet (1 m) high and
made of heavy poultry wire or 2-inch (5-cm) mesh woven
wire. To prevent burrowing under the fence, bury the
lower edge 10 to 12 inches (25 to 30 cm) in the ground
or bend the lower edge at an L-shaped angle leading
outward and bury it in the ground 1 to 2 inches (2.5 to
5 cm). Fences should extend 3 to 4 feet (0.9 to 1.2 m)
above the ground. Place an electric wire 4 to 5 inches
(10 to 13 cm) off the ground and the same distance
outside the fence. When connected to a UL-approved fence
charger, the electric wire will prevent climbing and
burrowing. Bending the top 15 inches (38 cm) of wire
fence outward at a 45o angle will also prevent climbing
over the fence. Fencing is most useful in protecting
home gardens and has the added advantage of keeping
rabbits, dogs, cats, and other animals out of the garden
area. In some instances, an electric wire alone, placed
4 to 5 inches (10 to 13 cm) above the ground, has
deterred woodchucks from entering gardens. Vegetation in
the vicinity of any electric fence should be removed
regularly to prevent the system from shorting out.
Devices Scarecrows and
other effigies can provide temporary relief from
woodchuck damage. Move them regularly and incorporate a
high level of human activity in the susceptible area.
Repellents None are
Toxicants None are
registered for woodchuck control.
Gas cartridge (carbon monoxide). The most common
means of woodchuck control is the use of commercial gas
cartridges. They are specially designed cardboard
cylinders filled with slow-burning chemicals. They are
ignited and placed in burrow systems, and all entrances
are sealed. As the gas cartridges burn, they produce
carbon monoxide and other gases that are lethal to
woodchucks. Gas cartridges are a General Use Pesticide
and are available from local farm supply stores, certain
USDA-APHIS-ADC state and district offices, and the
USDA-APHIS-ADC Pocatello Supply Depot. Directions for
their use are on the label and should be carefully read
and closely followed (see information on gas cartridges
in the Pesticides and Supplies and Materials sections).
Be careful when using gas cartridges. Do not use them in
burrows located under wooden sheds, buildings, or near
other combustible materials because of the potential
fire hazard. Gas cartridges are ignited by lighting a
fuse. They will not explode if properly prepared and
used. Caution should be taken to avoid prolonged
breathing of fumes.
Each burrow system should
be treated in the following manner:
1. Locate the main burrow
opening (identified by a mound of excavated soil) and
all other secondary entrances associated with that
burrow system. B-186
2. With a spade, cut a
clump of sod slightly larger than each opening. Place a
piece of sod over each entrance except the main
entrance. Leave a precut sod clump next to the main
entrance for later use. 3. Prepare the gas cartridge for
ignition and placement following the written
instructions on the label. 4. Kneel at the main burrow
opening, light the fuse, and immediately place (do not
throw) the cartridge as far down the hole as possible.
5. Immediately after
positioning the ignited cartridge in the burrow, close
the main opening or all openings, if necessary, by
placing the pieces of precut sod, grass side down, over
the opening. Placing the sod with the grass side down
prevents smothering the lit cartridge. Make a tight seal
by packing loose soil over the piece of sod. Look
carefully for smoke leaking from the burrow system and
cover or reseal any openings that leak.
6. Continue to observe the
site for 4 to 5 minutes and watch nearby holes. Continue
to reseal those from which smoke is escaping.
7. Repeat these steps
until all burrow systems have been treated in problem
areas. Burrows can be treated with gas cartridges at any
time. This method is most effective in the spring before
the young emerge. On occasion, treated burrows will be
reopened by another animal reoccupying the burrow
system. If this occurs, retreatment may be necessary.
Aluminum phosphide is a Restricted Use Pesticide and can
be applied only by a certified pesticide applicator.
Treatment of burrow systems is relatively easy. Place
two to four tablets deep into the main burrow. Plug the
burrow openings with crumpled newspapers and then pack
the openings with loose soil. All burrows must be sealed
tightly but avoid covering the tablets with soil. The
treatment site should be inspected 24 to 48 hours later
and opened burrows should be retreated.
Aluminum phosphide in the
presence of moisture in the burrow produces hydrogen
phosphide (phosphine) gas. Therefore, soil moisture and
a tightly sealed burrow system are important. The
tablets are presently approved for outdoor use on
noncropland and orchards for burrowing rodents. Tablets
should not be used within 15 feet (5 m) of any occupied
building or structure or where gases could escape into
areas occupied by other animals or humans. Storage of
unused tablets is critical — they must be kept in their
original container, in a cool, dry, locked, and
ventilated room. They must be protected from moisture,
open flames, and heat.
The legal application and
use of aluminum phosphide for woodchuck control may vary
from state to state. Check with your state pesticide
registration board, USDA-APHIS-ADC representative, or
extension agent when considering use of this material.
Aluminum phosphide should always be applied as directed
on the label.
Steel leghold and live traps. Traps may also be used
to reduce woodchuck damage, especially in or near
buildings. Both steel leghold and live traps are
effective. Trapping should be used in areas where gas
cartridges or aluminum phosphide may create a fire
hazard or where fumes may enter areas to be protected.
Woodchucks are strong animals and a No. 2 steel trap is
needed to hold them. Before using steel traps, consult
your state wildlife department or USDA-APHIS-ADC
representative for trapping regulations. Steel traps
should not be employed in areas where there is a
possibility of capturing pets or livestock. Live
trapping can sometimes be difficult, but is effective.
Live traps can be built at
home, purchased from commercial sources (see Supplies
and Materials), or borrowed. Bait traps with apple
slices or vegetables such as carrots and lettuce, and
change baits daily. Locate traps at main entrances or
major travel lanes. Place guide logs on either side of
the path between the burrow opening and the trap to help
funnel the animal into the trap. Check all traps twice
daily, morning and evening, so that captured animals may
be quickly removed. A captured animal can be relocated
to an area with suitable habitat where no additional
damage can be caused. The animal can also be euthanized
by lethal injection (by a veterinarian or under
veterinarian supervision), by shooting, or by carbon
Conibear® traps are effective in some situations. A set
in a travelway, such as between a wood pile and barn,
can be very effective. Sets can also be made at the main
entrance of the burrow system. Logs, sticks, stones, and
boards should be used to block travelways around the set
and/or to lead the animal into the set. No bait is
necessary for Conibear® sets. Conibear® 110s, 160s, and
220s are best suited for woodchuck control. Conibears®
are well suited for use near or under structures in
which fumigants and shooting present a hazard. Conibear®
110s will handle young, small animals, while 160s and
220s will also handle larger adults. Conibear® traps
kill the animal quickly and care should be taken to
avoid trapping domestic animals such as cats and dogs.
Some state or local laws prohibit the use of Conibear®
traps except in water. Consult your state wildlife
department or USDA-APHIS-ADC office for regulations.
In many states, woodchucks are considered game
animals. Therefore, if shooting is permitted, a valid
state hunting license may be required. In some states
there is no closed season, nor is there usually any
limit on the number of woodchucks that can be taken by
hunters. If shooting can be accomplished safely,
landowners and/or hunters can reduce or maintain a low
population of woodchucks where necessary. Landowners and
hunters should agree on hunting arrangements prior to
initiating any shooting activities. Another alternative
would be to have a professional USDA-APHIS-ADC
representative do the job. He or she will be familiar
with legalities and techniques. Contracting with a
Animal Damage Control professional would be especially
valuable when and where large numbers of woodchucks are
causing serious economic losses. Shooting can be used as
a follow-up to other, more substantial control
Rifles with telescopic
sights are commonly used in the sport shooting of
woodchucks. A variety of calibers can be used, but
.22-caliber centerfire rifles are most popular.
Occasionally, shotguns are used to eliminate woodchucks
that are causing damage. The objective is to remove the
animal as humanely as possible without wounding it.
Shotgun gauge, range, and shot size should be considered
when using this method. Use a 12-gauge with No. 4 to No.
6 shot. The range should be within 25 yards (23 m).
Carefully assess the area behind and around the target
for safety. Pellets can ricochet, causing injury or
serious damage in background areas. Use of a rifle or
shotgun should be conducted only if good shooting
I thank the state
directors of USDA-APHISADC, whose comments and editing
improved this publication. Figures 1 through 3 from
Schwartz and Schwartz (1981), adapted by Jill Sack
Burt, W. H., and R. P.
Grossenheider. 1976. A field guide to the mammals. 3d
ed. Houghton Mifflin Co., Boston. 289 pp.
Lee, D. S., and J. B.
Funderburg. 1982. Marmots. Pages 176-191 in J. A.
Chapman and G. A. Feldhamer, eds. Wild mammals of North
America: biology, management, and economics. The Johns
Hopkins Univ. Press, Baltimore, Maryland.
Marsh, R. E., and W. E.
Howard. 1990. Vertebrate pests. Pages 791-861 in A.
Mallis, ed. Handbook of pest control, 7th ed. Franzak
and Foster Co., Cleveland, Ohio.
Schwartz, C. W., and E. R.
Schwartz. 1981. The wild mammals of Missouri. Rev. ed.
Univ. Missouri Press, Columbia. 356 pp.
Whitaker, J. O. Jr. 1980.
Audubon Society field guide to North American mammals.
6th ed. Alfred A. Knopf, Inc. New York.
Scott E. Hygnstrom Robert
M. Timm Gary E. Larson
PREVENTION AND CONTROL OF
WILDLIFE DAMAGE — 1994
Division Institute of Agriculture and Natural Resources
University of Nebraska - Lincoln
United States Department
of Agriculture Animal and Plant Health Inspection
Service Animal Damage Control
Great Plains Agricultural
Council Wildlife Committee