Woodchucks

The woodchuck, also known as the groundhog or whistle pig, is one of Pennsylvania's most widely distributed mammals.
Woodchucks - Articles

Updated: August 14, 2017

Woodchucks

On occasion, the woodchuck's feeding and burrowing habits conflict with human interests. This fact sheet covers woodchuck biology, food habits, damage caused by woodchucks, and damage control methods.

The woodchuck (Marmota monax), also known as the groundhog or whistle pig, is one of Pennsylvania's most widely distributed mammals. 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 short tail is well covered with dark brown fur. Woodchucks usually are a grizzled brownish-gray, but white (albino) and black (melanistic) individuals can occasionally be found. Both sexes are similar in appearance, but the slightly larger males weigh an average of 5 to 10 pounds. The total length of the head and body averages 16 to 20 inches, and the tail is usually 4 to 7 inches 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.

General Biology

In general, woodchucks prefer to construct their burrows in open farmland and wooded or brushy areas adjacent to open land. However, they also can be found in woodlands, on abandoned farms, and occasionally in suburban areas where the combination of food and cover provides satisfactory habitat. Burrows commonly are located in fields and pastures, along fence rows, and stone walls, roadsides, and near building foundations or the bases of trees.

A woodchuck burrow serves as home to the woodchuck for mating, raising young, hibernating, and escaping danger. Woodchuck burrows can be identified by the large mound of excavated earth at the main entrance. On this mound, which is constantly renewed by debris from within, the woodchuck frequently sits to look for danger. From the entranceway, which is 10 to 12 inches in diameter, the burrow goes down at a rather steep angle and then levels off into a narrower tunnel. A single nest chamber, used for sleeping and raising young, is formed at the end of the burrow. Other rooms are used as toilet areas. By separating nest areas from toilet areas, the den is kept relatively clean and free from disease. In addition to the main entranceway, there are commonly one to three secondary entrances. These secondary entrances are dug from below and do not have mounds of earth beside them. They are often well hidden and sometimes difficult to locate. Woodchucks usually range only 50 to 150 feet from their den and can retreat quickly into the burrow when threatened.

Woodchucks primarily 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. When not feeding, they sometimes bask in the sun during the warmest periods of the day. Woodchucks are also good climbers and sometimes can be seen in lower tree branches.

Woodchucks are among the few mammals that enter into true hibernation. Hibernation varies with latitude, but generally begins near the end of October or early November and continues until late February and March. Males usually come out of hibernation before females, and juvenile males may travel long distances in search of a mate. Woodchucks breed in March and April. A single litter of two to six (usually four) 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. Young woodchucks frequently occupy abandoned dens or burrows. The numerous new burrows that appear during late summer are generally dug by older woodchucks. Once occupied, a burrow system may be used for several seasons. Old burrows not in use by woodchucks provide cover for rabbits, weasels, and other wildlife.

Woodchuck tracks

Woodchucks have a life span of about three to four years. Their primary predators include hawks, owls, foxes, coyotes, bobcats, weasels, dogs, and humans. Many woodchucks are killed on roads by automobiles.

Description of Damage

On occasion, the woodchuck's feeding and burrowing habits conflict with human interests. Damage often occurs on farms, in home gardens, orchards, and nurseries, around buildings, and sometimes around dikes. Damage to crops such as alfalfa, soybeans, beans, squash, tomatoes, and peas can be costly and extensive. Homeowners may lose their entire tomato patch. Fruit trees and ornamental shrubs may be damaged by woodchucks as they gnaw on woody vegetation. 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 building foundations.

Legal Status

In Pennsylvania, woodchucks are classified as game animals. Game protection is removed when woodchucks damage personal property. In that case, woodchucks can be controlled by the property owner using the lawful means described in this fact sheet.

Damage Control

Woodchuck damage is a common problem, but it can be controlled in a number of ways. If you feel that you cannot properly handle the damage control techniques, many wildlife pest control operators are available throughout the state. Contact your county extension office or the yellow pages for information regarding these operators.

Exclusion

The most permanent control method is fencing. However, the practicality of fencing depends on the size of the area to be fenced. Fences should be at least 3 feet high and made of heavy poultry wire or 2-inch woven-mesh wire. To prevent woodchucks from burrowing under the fence, bury the lower edge 12 inches in the ground with the lower 6 inches bent at an L-shaped angle leading outward. Fences should extend 3 to 4 feet above the ground. As an additional measure, place an electric wire 4 to 5 inches off the ground and the same distance outside the fence. When connected to a fence charger, the electric wire will prevent climbing and burrowing. Bending the top 15 inches of wire fence outward at a 45° angle will also prevent woodchucks from climbing over the fence. Fencing is most beneficial when used to protect home gardens and has the added advantage of keeping rabbits, dogs, cats, and other animals out of the garden area. In some instances, a single electric wire placed 4 to 5 inches 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.

Mesh fence sunk into the ground

Frightening

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

No repellents are registered for use against woodchucks in Pennsylvania.

Toxicants

No toxicants are registered for woodchuck control in Pennsylvania.

Fumigants

Two types of fumigants are registered for use on woodchucks. Both work by producing a toxic gas in the burrow system. These gases are toxic to other wildlife species. Follow label instructions and use only on burrows that are actively used by woodchucks.

Gas Cartridges (Carbon monoxide)

The most common means of woodchuck control is the use of commercial gas cartridges. These specially designed cardboard cylinders are filled with slow-burning chemicals. They are ignited and placed in a burrow system, and all entrances to the burrow are then 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 often are available from local farm supply stores. Directions for their use are on the label and should be closely followed.

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:

  • Locate the main burrow opening (identified by a mound of excavated soil) and all other secondary entrances associated with that burrow system.
  • 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.
  • Prepare the gas cartridge for ignition and placement by following the written instructions on the label.
  • Kneel at the main burrow opening, light the fuse, and immediately place (do not throw) the cartridge as far into the hole as possible.
  • Immediately after positioning the ignited cartridge in the burrow, close the main opening by placing the piece of precut sod, grass side down, over the opening. Placing the sod with the grass side down prevents the lit fuse from being smothered. 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.
  • Continue to observe the site for four to five minutes and watch nearby holes. Continue to reseal those from which smoke is escaping.
  • 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

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 tightly sealed, but try to 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. These tablets are presently approved for outdoor use on noncropland and orchards. Tablets should not be used within 15 feet 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, and must be protected from moisture, open flames, and heat. Aluminum phosphide should always be applied as directed on the label.

Trapping

Live traps should be at least 10 x 10 x 24 inches in size. A live trap may be placed either at the burrow entrance, in major travel lanes, or at the site of damage. Place guide logs on either side of the trap to help funnel the animal into it. A trap should also be covered with dark canvas or grass to conceal it.

Bait traps with apple slices, carrots with tops, cantaloupe pieces, lettuce, cabbage, or ample amounts of fresh peas. Replace the bait daily and remove any wilted pieces from the trap. Where food is abundant, woodchucks may not enter live traps. In that case, block the trap door open for several days to allow the animal to take the bait regularly. Once this has happened, set the trap. Check all traps twice daily, morning and evening, so that captured animals may be quickly removed.

After the animal is trapped, it should be humanely euthanized or released elsewhere on the landowner's property. Since woodchuecks are considered a potential rabies vector, the Game Commission does not allow them to be relocated to other properties.

Shooting

Woodchucks can be legally shot anytime of the year if they are damaging property. There is no bag limit on woodchucks, but hunters must possess a valid Pennsylvania hunting license. If shooting can be accomplished safely, landowners and/or hunters can either reduce woodchuck populations or maintain a low population of woodchucks where necessary. Landowners and hunters should agree on hunting arrangements prior to initiating any shooting activities. Shooting also can be used as a follow-up to other control activities.

Summary

Woodchucks often cause problems in agricultural and sub- urban areas. They can damage vegetable crops, and their burrows can potentially damage tractors and lawn equipment. There are many forms of woodchuck damage control available to homeowners. Exclusion is the most effective way to alleviate vegetation damage. As with all control techniques, make sure woodchucks are responsible for the damage before taking action.

Authors

Prepared by Shannon N. Thurston, assistant wildlife extension specialist; Margaret C. Brittingham, professor of wildlife resources; and Lisa M. Williams-Whitmer, former assistant wildlife extension specialist.

Illustrations © Penn State College of Agricultural Sciences

Acknowledgments

Portions of this fact sheet were adapted from Prevention and Control of Wildlife Damage, a two-volume manual edited by Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson and published by the University of Nebraska's Cooperative Extension Division, USDA APHIS-ADC, and the Great Plains Agricultural Council's Wildlife Committee. Partial funding for this fact sheet was provided by the Wild Resource Conservation Fund.

Instructors

Avian ecology Effects of shale gas development on forests and birds forest songbirds Human impacts on bird population Wildlife habitat management on private lands Landscaping for birds and wildlife

More by Margaret C. Brittingham, Ph.D.