Woodchucks or groundhog (Marmota monax)

Click here for “Wildlife Damage Management Fact Sheet Series–Woodchucks” from Cornell University 

Size: 

20–27″ long, excluding tail; 5–12 pounds. 

Signs of their presence: 

Adults often seen basking in the sun, in a grassy area, on a fence post, stone wall, large rock, or fallen log—always near its burrow. 

Sounds: Occasional sharp whistles and low churrs, given at times of danger. 

Odor is distinctive. Will often see flies around an active burrow. 

Scat: Rarely seen (woodchucks excavate a privy off their main burrow). 

Evidence of their feeding: Chewed wood. Chewing on fresh plants similar to that of rabbits; difficult to pin on woodchucks without supporting evidence. 

Dens: Will see a large mound of dirt and stones by the main entrance to their burrow; the secondary entrances, which were dug from the inside, generally don’t have a dirt mound by their opening. Well-worn trail from entrance to entrance, or to the garden. 

Diet: 

Herbivore. Woodchucks eat succulent grasses, weeds, clover, fruits (apples, cherries, pears), berries, field and garden crops (cabbage, lettuce, beans, peas, carrots, alfalfa, soybeans), and ornamental plants (they love phlox). They’ll climb trees to take fruits such as cherries, apples, and pears. 

Typical activity patterns: 

Social style: Generally solitary. 

Daily activity: Diurnal, most active in the early morning and evening. They rely on dew as their water source. Woodchucks have good eyesight, and are good swimmers. They’ll climb trees up to a height of about 20 ft, although more usually, they keep to 8–12 ft. 

Hibernator? Yes. Hibernates deeply from the time of the first heavy frost through early spring. Occasionally hibernates in small groups. 

Migrates? No. 

Where found: 

In Michigan woodchucks can be found everywhere, including the Upper Peninsula.  

Habitat: 

 Meadows, woodlots, hay fields, pastures, hedgerows, idle fields, parks, suburbs. Dens usually found in open fields; near fence rows or woodland edges; under barns, sheds, porches, decks, stone walls, and wood piles. 

Territory and home range: 

 Territorial. Woodchucks may skirmish to establish dominance. Subordinate woodchucks avoid dominant ones. Home ranges overlap and are usually small. Woodchucks rarely travel more than 50 yards from their den, even to feed. Their burrows can be 2–5 feet deep and as much as 60 feet long. There are usually 2 or 3 (but perhaps as many as 5) entrances, possibly including a well-hidden, straight-down “plunge hole”. 

Breeding habits: 

Pair bonding style: Polygamous. Females raise young alone. 

Breeding dates: Late February through March. 

Birthing period: Late March to early May. Gestation takes about 31 days. 

Litter size: 3–4. 

Weaning dates: at 5–6 weeks. 

Amount of time young remain with parents beyond weaning date: Young stray from burrow alone at 6–7 weeks, mid-June to early July. Mother drives young from her burrow by July. 

Common nuisance situations: 

Time of year: Calls peak in July and August, although their damage may begin in spring and last into the fall. 

What are they doing? 

Feeding, or just filing down their front teeth, which never stop growing. Woodchucks raid gardens, fields, lawns, orchards, nurseries, and may gnaw or claw on shrubs and fruit trees. Occasionally chew on outdoor furniture, decks, and siding while scent-marking or filing their teeth. 

Marking their territories: They may strip off the bark at the base of a tree that’s near their burrow entrance. 

Burrowing. Look for burrow entrances among shrubs near vegetable and ornamental gardens; under woodpiles, brush piles, and stone walls; under sheds, porches, decks, and crawl spaces. Burrows in fields may damage agricultural equipment, while those in pastures may trip livestock, resulting in injuries. 

Disease risks: Low. Mange, rabies (rarely), raccoon roundworm. 

Legal status in Michigan: 

Unprotected. Woodchucks can be trapped or shot any time of the year. However, if one decides to hunt woodchucks it must be done in accordance with the hunting and firearm laws. 

May be taken year-round if they are doing or about to do damage on private land 

Best practices 

Just when you thought it was all over, year-old woodchucks will occupy abandoned burrows. You can try filling in the burrows, but they may re-open the holes. 

Remove artificial food sources and shelter: 

Remove brush piles and debris 

Trim tall grass and brush around the tree line and structure 

Protect vulnerable crops: 

Erect a “rat wall” fence around gardens, orchards, and fields. Make sure the woodchucks can’t climb over or dig under this barrier. Use 1–1 1/2″ chicken wire.  

The fence should be 4 feet high and buried 2 feet deep;  

Bend the edge outward into a “L” shape that sticks out at a 90° angle to prevent the woodchucks from burrowing underneath it.  

Bend the top 15″ of the fence out at a 90° angle to keep them from climbing over it, leave this portion a little flimsy  

 Add an electric wire strung 4–5″ above ground level, and 4–5″ from the outside of the fence. 

Another modification of the rat wall design. Use 2 × 4″ welded wire that’s 2 ft. high, bottom buried in the L-shaped shelf as described above. String an electric wire across the top of the fence. (Durable and effective but more expensive.) 

Keep them from denning under buildings: 

First step: Remove any current residents. Exclude them with a one-way door when young are old enough to be mobile. 

If this is a preventive action, or there are no young present, can: 

Screen areas under decks, porches, and houses with the rat wall fence, as described above. Attach the top of the fence to the structure. 

If young are present, remove the entire family before blocking the entrance to their den: 

If the young are older and mobile, install a one-way door over the entry hole. They’ll leave but won’t be able to re-enter. 

Trap and release strategies to reduce the risk of orphaning wildlife:  

The best way to prevent orphaning is to convince your customers to wait until the young are mobile before removing, repelling, or excluding the family from the site. If that’s unacceptable, you can try to capture and remove both the female and all of her young and hope that she will retrieve them and continue to care for them. 

Capture the mother and young. Cover cages during transport to minimize stress. Release them on-site, preferably in the morning, or euthanize them.  

Place the female and young in a release box. Many NWCOs use a simple cardboard box, others use a wooden nest box, such as a wood duck box, and some prefer plastic boxes. Use a larger box with a 7″ hole. (One NWCO recommends a 2 × 2 × 1 ft. box.) 

Make sure the animal cannot immediately get out of the box by covering the hole. Then move them to a quiet place outdoors. Remove the cover so the female can get out of the box.  

Another option is to build a box with a sliding door. Leave the door open about an inch, to keep the heat inside but make it easy for the female to slide it fully open so she can retrieve her young. 

Some NWCOs prefer to use heated release boxes. Use heat when appropriate, and make sure that the box doesn’t get too hot. You may want to provide heat in just one area. Also, assume that if you put something in the box, they will chew on it. Don’t give them access to anything that they shouldn’t eat, such as wires. That means that if you choose to use a household heating pad as the heat source, make sure the animals can’t reach the wires. To avoid that problem, build boxes with a double floor, place the heating pad in the space between the floors. Other options for heat sources include microwaveable heating pads and warm soapstones. 

If you can’t catch the female, put the young in the release box and locate it as close to the entry site as possible. 

Cover the hole to the burrow with a soft plug to make sure that no woodchucks are still using it. Check the next day to see if the young are still there. If so, they’ve probably been abandoned. There hasn’t yet been enough research on this technique, so its effectiveness is unknown. It’s likely to be more effective with older, more experienced females; younger females might abandon their young more readily. 

Trapping strategies: 

Live traps: 

Cage trap should be at least 10x10x24″. Double door traps should be at least 10 × 10 × 30″. 

Traps should be closed at night to avoid catching a non-target species 

Conceal the trap, using grass or canvas. 

Bait the trap with apples, cantaloupe, cabbage, carrots with the tops, peas, or lettuce 

Do not put too much bait in the trap 

Using a trap that already had a woodchuck in it may be helpful 

Taking dirt from the mound outside the burrow can also be beneficial  

Choose the size of trap based on the size of the burrow’s hole, but realize that woodchucks can wreck a smaller trap. 

Foothold traps, #1 or 1 1/2. Must be covered 

Check traps twice daily, and provide shade and protection from weather. Woodchucks can overheat easily. 

Clean any brush away from the opening of the trap, or it may interfere with the door. 

Can also set trap without bait, placing it directly in front of the hole. Dig down a bit and use fencing to guide the woodchuck into the trap. 

Lethal traps: 

Spring is the best time for control, when the adults are active but before the young are born. It’s also easier to see the burrows then, and other animals are less likely to be inside. Woodchuck burrows provide shelter to several species. 

Body-gripping trap, or a 5 × 5 Buckeye, placed at the entrance to the burrow. To reduce the risk of catching pets or unintended wildlife, cover the hole and the trap with a weighted box or hardware cloth. Another option is to add a one-way trigger to the trap, so it only fires when the woodchuck is leaving its burrow. See chapter five for details. 

Modify the trigger to help ensure a top-to-bottom strike (which is more humane) and to prevent the woodchuck from refusing to enter the trap. Woodchucks don’t like to have anything brush against their eyes or whiskers, so separate the trigger and center it on the bottom of the trap. Proper positioning helps to ensure a cleaner, more humane catch. 

Other lethal techniques: 

Carbon monoxide gas cartridges may be used to kill woodchucks in their burrows. These gas cartridges do pose a fire hazard so don’t use them near buildings, under sheds, or near stumps. They could ignite grass, buildings, gasoline, and other flammable objects. 

Do not use this method from October on, wait until they come out of hibernation. Woodchucks will seal off their burrows so the fumigation will be ineffective.  

Preferred killing methods: 

CO2 chamber 

Lethal trap 

Shooting, using a shotgun, a .22 caliber rifle, or a centerfire rifle where safe (target the head, if no rabies testing is needed, or the heart/lungs) 

Lethal injection of barbiturate, if possible 

Acceptable killing methods: 

Stunning and chest compression 

Pesticides (carbon monoxide fumigants) for NWCOs with a commercial pesticide applicator license. 

Control Methods that don’t work particularly well, or aren’t legal in Michigan: 

Filling their burrows with as many rocks as possible may make it unsuitable. However, they may just remove the rocks.  

Woodchucks do not like the smell of lavender, plant a row of lavender around a garden or vulnerable area to prevent the woodchuck from entering 

Commercial deer and rabbit repellents, as well as some pesticides thought to repel woodchucks, weren’t that effective at keeping them away from crops.  

For information on legal pesticides click the following link, https://www.michigan.gov/mdard/0,4610,7-125-1569_16988_35291—,00.html