Groundhogs (Woodchucks)

A groundhog, also called a woodchuck, is a large burrowing ground squirrel (Marmota monax) that weighs 5-12 pounds and lives in the eastern and central US. It eats grasses and garden plants by day and digs big burrows under sheds, decks and field edges, which is where most conflicts with homeowners start.

Groundhogs are not aggressive and rarely bite, but one animal can strip a vegetable garden in a few days, and its tunnels can undermine slabs, steps and shed floors. Below: how to identify one, how it differs from gophers and marmots, its yearly cycle, and what actually keeps it out.

What a groundhog looks like

• Body: stocky, low and heavy, 16-27 inches long including a short, bushy 4-7 inch tail.
• Fur: grizzled brown to gray-brown with lighter tips; feet dark brown to black.
• Head: short ears, small dark eyes, large white or cream incisors that are visible when it chews.
• Behavior: often sits bolt upright at the burrow mouth to look around; gives a sharp whistle when alarmed (hence "whistle-pig").
• Activity: active in daylight, mostly early morning and late afternoon. That alone separates it from most other yard diggers, which work at night or underground.

They are good swimmers and can climb fences and low trees, which matters when you plan a fence.

Groundhog vs gopher, woodchuck and marmot

Woodchuck vs groundhog: same animal, two names. Regional habit decides which one people use.

Groundhog vs gopher: people mix these up because both dig. The differences are easy to see:

If you have many small mounds with no open holes, it's a gopher or a mole, not a groundhog.

Marmot vs groundhog: the groundhog is a marmot. In the western mountains you'll meet the yellow-bellied and hoary marmots, which look similar but live in rocky slopes and high meadows. In eastern lowlands and suburbs the marmot is the groundhog.

Burrows and signs

The burrow is the clearest sign. Main entrances are 10-12 inches across with a large fan of soil and rocks in front; there are usually one or two hidden "plunge holes" without dirt nearby. The tunnel system can run 2-6 feet deep and 25-50 feet long, with separate nest and toilet chambers.

Favorite sites: under sheds, decks, porches and concrete slabs, along fence lines, at the edge of woods and in brushy field borders.

Other signs:

• Garden plants eaten down to the stems, often in daylight. Beans, peas, squash, lettuce, cabbage family and melons are favorites.
• Gnawed fruit, clipped flowers, chewed young tree bark.
• Worn paths through grass between the burrow and the garden.
• Damaged irrigation lines and wiring near burrows.

Groundhog burrows are later used by foxes, skunks, rabbits and opossums, so an old hole with fresh activity isn't always a groundhog.

Yearly cycle and hibernation

Groundhogs are true hibernators. In fall they fatten up, then sleep from roughly October-November to February-March, with body temperature dropping to around 40°F and heart rate to a few beats a minute. In the South the hibernation period is shorter.

Males wake first, often in February, and visit females' burrows. Mating follows in March-April. (Groundhog Day on February 2 is folklore, not biology.)

Baby groundhogs

After about a month of gestation, a litter of 2-6 baby groundhogs (usually 4-5) is born in April or May, blind and hairless. They first come out of the burrow at about 6 weeks, in June, and disperse to dig their own burrows by mid to late summer. That's why you suddenly see several young groundhogs in July.

If you see a baby near a burrow, leave it be. Don't evict or exclude a groundhog from April through July: you'd trap young in the burrow or orphan them.

Groundhog lifespan

In the wild most groundhogs live 2-3 years; a few reach 6. Predators include foxes, coyotes, hawks, owls and dogs; cars and people kill many. Captive groundhogs can reach 10-14 years.

Are groundhogs dangerous?

Not to people in normal circumstances. They avoid contact and flee to the burrow. A cornered groundhog will hiss, chatter its teeth and bite hard, so don't grab one or let dogs corner it.

Rabies is possible: groundhogs are among the rodents most often reported rabid in the eastern US, though it's still uncommon. Treat a groundhog that approaches people, acts confused or partly paralyzed as possibly rabid and call animal control. If bitten or scratched, wash with soap and water and call your doctor.

The bigger risk is structural: burrows under slabs, foundations and steps can cause settling and cracking, and tunnels in fields or lawns are an ankle and mower hazard.

Groundhog repellent: what works and what doesn't

• Fencing works best. Use welded wire or chicken wire at least 3-4 feet high, with the bottom foot bent outward in an L and buried 10-12 inches, or simply laid on the ground and pinned. Leave the top 12-15 inches unattached and floppy so a climbing groundhog falls back. A single electric strand 4-5 inches above ground outside the fence makes it much more reliable.
• Commercial repellents (castor oil, capsaicin/hot pepper, putrescent egg, predator urine) can make a small bed less attractive for a while. They wash off, need weekly reapplication and don't make an established animal leave its burrow.
• Ammonia rags, mothballs, gas cartridges in the burrow: mothballs used this way are an off-label pesticide use; gas cartridges are EPA-registered but only legal per label and risky next to buildings. Don't use them under a deck or house.
• Ultrasonic devices, spinning pinwheels: no good evidence they work.
• Exclusion of an existing burrow: after mid-August (once young have dispersed) or before April, loosely plug the hole, wait for the groundhog to leave, then install an L-shaped wire skirt so it can't dig back under the shed or deck.

Live trapping (a 10x12x32-inch cage baited with cantaloupe, apples or fresh greens) is common, but many states restrict relocating wildlife, and relocated groundhogs often die or come back. Check your state wildlife agency rules first, or hire a licensed wildlife control operator; a typical groundhog removal runs roughly $150-$400 in most areas (approximate).

Related yard animals

Groundhogs share yards with voles, moles, skunks (which often move into old groundhog burrows) and squirrels. Matching the damage to the right animal is the first step before you buy any trap or product.