B-183

WOODCHUCKS

Rene M. Bollengier, Jr.

Assistant Regional Director (retired)

USDA-APHIS-

Animal Damage Control

Concord, New Hampshire 03302-2398

Fig. 1. Woodchuck, Marmota monax

Damage Prevention and

Control Methods

Exclusion

Buried welded or woven wire fences.

Single-strand electric fences.

Frightening Devices

Scarecrows and other effigies.

Repellents

None are registered.

Toxicants

None are registered.

Fumigants

Gas cartridges.

Aluminum phosphide.

Trapping

Live traps.

No. 2 leghold traps.

Conibear® traps.

Shooting

Effective where legal and safe.

Identification

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 mar-

mots. It is usually grizzled brownish

gray, but white (albino) and black

(melanistic) individuals can occasion-

ally be found. The woodchuck’s com-

pact, 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 dark brown.

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Coop erat ive Extension 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

B-184

Both sexes are similar in appearance,

but the male is slightly larger, weigh-

ing 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 con-

cealed 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.

Range

Woodchucks occur 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, southeast-

ern Nebraska, eastern Kansas, and

northeastern Oklahoma, as well as

south to Virginia and northern Ala-

bama (Fig. 2).

Habitat

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 op en, grassy mead-

ows 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 mou nds 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 pro-

tection when threatened.

Food Habits

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 feed-

ing, 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 mam-

mals 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 (usu-

ally 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 o f the woodchuck.

Side entrance

Nest

chamber

Main

entrance

Fig. 2. Range of the woodchuck in North America.

B-185

by older woodc hucks. 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 sea-

son or based on the availability of

food. Woodchucks maintain sanitary

den sites and burrow systems, replac-

ing nest materials frequently. A bur-

row 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 bur-

rows not in use by woodchucks pro-

vide 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 usu-

ally made when the animal is startled

at the entrance of the burrow. The pri-

mary predators of woodchucks

include hawks, owls, foxes, coyotes,

bobcats, weasels, dogs, and humans.

Many woodchucks are killed on roads

by automobiles.

Damage

On occasion, the woodchuck’s feeding

and burrowing habits conflict with

human interests. Damage often occu rs

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 c ostly and

extensive. Fruit trees and ornamental

shrubs are damaged by woodchucks

as they gnaw or claw woody vegeta-

tion. Gnawing on u nderground 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 consid-

ered 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 Con-

trol representative, or extension agent

before shooting and/or trapping prob-

lem individuals.

Damage Prevention and

Control Methods

Exclusion

Fencing can help reduce woodchu ck

damage. Woodchucks, however, are

good climbers and can easily scale

wire fences if precau tions are not

taken. Fences should be at least 3 feet

(1 m) high and made of heavy p oultry

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 elec-

tric wire 4 to 5 inches (10 to 13 cm) off

the ground and the same distance out-

side the fence. When connected to a

UL-approved fence charger, the elec-

tric wire will prevent climbing and

burrowing. Bending the top 15 inches

(38 cm) of wire fence outward at a 45

o

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.

Frightening Devices

Scarecrows and other effigies can pro-

vide temporary relief from woodchuck

damage. Move them regularly and

incorporate a high level of human

activity in the susceptible area.

Repellents

None are registered.

Toxicants

None are registered for woodchuck

control.

Fumigants

Gas cartridge (carbon monoxide).

The most common means of wood-

chuck control is the use of commercial

gas cartridges. They are specially de-

signed 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 p rolonged 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 bur-

row 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 igni-

tion 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 open-

ings, if necessary, by placing the

pieces of precut sod, grass side

down, over the opening. Placing the

sod with the grass side down pre-

vents 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 prob-

lem areas.

Burrows can be treated with gas car-

tridges 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. Aluminum

phosphide is a Restricted Use Pesticide

and can be applied only by a certified

pesticide applicator. Treatment of bur-

row 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 bur-

rows should be retreated.

Aluminum phosphide in the presence

of moisture in the burrow produces

hydrogen phosp hide (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. Tab-

lets 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 applic ation and use of alumi-

num phosphide for woodchuck con-

trol may vary from state to state.

Check with your state pesticide regis-

tration 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.

Trapping

Steel leghold and live traps. Traps

may also be used to reduce wood-

chuck 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 regula-

tions. Steel traps should not be

employed in areas where there is a

possibility of capturing p ets or

livestock.

Live trapping can sometimes be diffi-

cult, but is effective. Live traps can be

built at home, purchased from com-

mercial 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 ani-

mal 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 veterinar-

ian supervision), by shooting, or by

carbon dioxide gas.

Conibear® traps. 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 fumi-

gants and shooting p resent 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. S ome state or local laws pro-

hibit the use of Conibear® traps except

in water. Consult your state wildlife

department or USDA-APHIS-ADC

office for regulations.

Shooting

In many states, woodchucks are con-

sidered 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

B-187

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 pro-

fessional would be especially valuable

when and where large numbers of

woodchucks are causing serious eco-

nomic losses. Shooting can be used as

a follow-up to other, more substantial

control activities.

Rifles with telescopic sights are com-

monly used in the sport shooting of

woodchucks. A variety of calibers can

be used, but .22-caliber centerfire rifles

are most popular. Occasionally, shot-

guns are used to eliminate wood-

chucks that are causing damage. The

objective is to remove the animal as

humanely as possible without wound-

ing 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 conditions exist.

Acknowledgments

I thank the state directors of USDA-APHIS-

ADC, whose comments and editing improved

this publication.

Figures 1 through 3 from Schwartz and

Schwartz (1981), adapted by Jill Sack Johnson.

For Additional

Information

Burt, W. H., and R. P. Grossenheider. 1976. A

field guide to the mammals. 3d ed.

Houghton Mifflin Co., Bosto n. 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: biolo gy, 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.

Editors

Scott E. Hygnstrom

Robert M. Timm

Gary E. Larson