Illinois is home to one of North America’s most dedicated hibernators — and if you’ve been watching for signs of life near a field edge or a backyard burrow, late winter is exactly the right time to pay attention. The marmot species that calls Illinois home spends up to four months underground each year, emerging in a predictable seasonal rhythm that nature-watchers can learn to anticipate.
In this guide, you’ll learn which marmot lives in Illinois, when it goes underground and when it comes back out, what it does in those first critical days after waking, where to find it across the state, and how to read the signs that one is active near you.
Which Marmot Species Live in Illinois
If you’re searching for marmots in Illinois, there is one species to focus on: the groundhog, also known as the woodchuck or whistle pig. The groundhog (Marmota monax), also known as the woodchuck, is a rodent of the family Sciuridae, belonging to the group of large ground squirrels known as marmots. It is the only marmot species with a native, established presence in the state.
Groundhogs, Marmota monax, are Illinois’ largest squirrel and one of the state’s few hibernating species. They belong to the family Sciuridae — the squirrel family — and are related to other marmots that occur in the western United States. Western marmot species such as the yellow-bellied marmot and hoary marmot are mountain and alpine animals; they do not naturally occur in Illinois.
The woodchuck is a stocky animal with a relatively flat head, blunt muzzle, short legs, and a bushy tail. Its fur is yellowish-gray brown to blackish, with the underside often lighter. Woodchucks have small ears and large black eyes. Woodchucks weigh 7 to 14 pounds and are approximately 20 to 25 inches long, including the tail.
Key Insight: The terms “groundhog,” “woodchuck,” and “whistle pig” all refer to the same animal — Marmota monax — Illinois’ only native marmot species.
Groundhogs are widespread throughout Illinois, found in virtually every county, from the northern regions bordering Wisconsin to the southern tip near the confluence of the Ohio and Mississippi Rivers. Woodchuck numbers appear to have decreased in Illinois in recent decades, though the species remains common across the state’s varied landscapes.
When Do Marmots Hibernate in Illinois
The groundhog’s hibernation is one of the most dramatic seasonal transitions of any mammal in Illinois. Unlike animals that simply slow down in winter, groundhogs enter a physiological state that is profoundly different from normal sleep.
Groundhogs are true hibernators, with drastic reductions in levels of physical activity and bodily functions. Leaving their summer burrows in October and November, they move to winter burrows to hibernate. Winter burrows are often dug in wooded areas and have only one opening. The hibernation nest is located at the end of the burrow, lined with grass, and blocked off with soil during hibernation.
During hibernation, the groundhog’s body undergoes remarkable changes. Researchers have found that while in hibernation, a woodchuck’s body temperature drops from about 97°F to 34°F, its breathing slows to approximately one breath every six minutes, and its heart beats only four times per minute. As one of Illinois’ few true hibernators, the groundhog may be underground for as many as four months depending on where they live.
Pro Tip: Groundhogs do not store food for winter. They survive entirely on fat reserves built up through intensive late-summer and fall feeding — so a well-fed groundhog in October is preparing for months underground.
Groundhogs hibernate longer in northern latitudes than southern latitudes. This means a groundhog in the Chicago area may stay underground somewhat longer than one in far southern Illinois near the Ohio River. Hibernating woodchucks lose as much as half their body weight by February.
When Do Marmots Come Out of Hibernation in Illinois
The moment Illinois groundhogs begin to stir is one of the quieter signs of the approaching season. You won’t usually see it announced dramatically — it happens gradually, guided by temperature and internal biology rather than any fixed date on a calendar.
Unlike most mammals in Illinois, woodchucks are true hibernators. They begin hibernation in October or November and come out of hibernation in mid- to late February. Beginning in late February and March, depending on the weather, groundhogs will begin coming out of hibernation.
The timing is not uniform across the state or even within a single population. Here in Illinois, groundhogs do typically emerge from hibernation in February, according to the University of Illinois Extension — however, they do not typically emerge so early in the month. Most male woodchucks that live in DuPage forest preserves are likely to hibernate until mid-February.
Important Note: Male groundhogs emerge before females. The first sightings of the season are almost always males, which wake earlier to scout territory and locate mates before full spring activity begins.
Male groundhogs emerge from their dens temporarily in early February, then reemerge in March to mate. Male groundhogs will wake up for one of these moments of arousal and emerge from their dens, typically sometime in February, to stumble sleepily around making house calls to females living in their two-to-three-acre territory. The males eventually head back to their own burrows for another round of torpor before they emerge again to mate in early spring.
By March, both males and females are consistently above ground and active. As one of Illinois’ few true hibernators, the groundhog may be underground for as many as four months depending on where they live. Except for extreme weight loss, they tend to emerge unharmed in February. These short-legged nibblers then move into more open areas to live closer to food sources and will dig new, more elaborate burrows, leaving their winter bed behind.
What Marmots Do Immediately After Hibernation in Illinois
Waking from hibernation is not a sudden event. The groundhog’s body transitions gradually from deep torpor to full alertness, and the animal’s first priorities after emerging reflect the biological pressures it faces after months underground.
Generally, the woodchuck’s body will go through a process of fast and slow heart rates, pushing blood flow around as it comes out of different states of torpor. Finally, the woodchuck is fully awake, usually about 30% lighter than when it went into hibernation.
The first priority is not food — it’s finding a mate. Beginning in late February and March, groundhogs come out of hibernation not to predict the weather, as folklore would suggest, but rather to find food as they will have lost a large portion of their body weight during hibernation, and to find a mate for the year. Male woodchucks emerge from hibernation earlier than females in order to establish territories, dominance hierarchies, and to search for mates.
Pro Tip: If you spot a groundhog in late February wandering slowly and looking somewhat thin, you’re likely seeing a male in his brief first-emergence phase — checking in on nearby females before retreating underground again for a few more weeks.
After mating, feeding quickly becomes the dominant behavior. They emerge from hibernation with some remaining body fat to live on until the warmer spring weather produces abundant plant materials for food. Shortly after they go looking for mates, newly-awakened groundhogs remember they haven’t eaten for five months. Groundhogs tend to forage and eat more than ever in spring, especially when they’re caring for newborn babies.
Groundhogs usually have one litter per year that averages four or five young born in April. Thermoregulatory basking is also common — groundhogs spend time sunning near burrow mouths to warm up after cold nights or after spring emergence. If you see one sitting motionless near a burrow entrance on a mild morning, it is likely doing exactly this.
Where to Spot Marmots in Illinois
One of the most accessible aspects of watching groundhogs in Illinois is that you don’t need to travel far. In Illinois, woodchucks can be found nearly everywhere — meadows, woodlots, hay fields, pastures, hedgerows, idle fields, parks, and suburbs.
What groundhogs really like is edge habitat — where a forest or wooded lot meets an open grassy area. They can forage for food in the grass while keeping an eye out for predators — coyotes, hawks, or foxes — and retreat if necessary. This preference for habitat edges makes roadsides, forest preserve boundaries, and the margins of agricultural fields some of the most reliable places to look.
| Habitat Type | What to Look For | Best Time to Visit |
|---|---|---|
| Forest preserve edges | Burrow mounds near tree lines | Early morning, late afternoon |
| Agricultural field margins | Animals feeding in open grass | Morning, when dew is present |
| Roadsides and fencerows | Upright sentinel posture near burrows | Mild spring days, late February–April |
| Suburban parks and office grounds | Burrows under shrubs or near foundations | Any daylight hour in spring |
| River corridors | Animals along embankments | Spring and early summer |
Northern Illinois groundhogs are abundant, often seen in agricultural fields and along roadsides. In central Illinois, they are common in both rural and suburban areas, frequently inhabiting parks and gardens. In southern Illinois, while their density may be slightly lower due to habitat differences, they are still present and active.
Suburban office parks have become a sweet spot for groundhogs, according to wildlife researchers. “They can graze on all that grass and not have to cross a lot of roads.” The Chicago River also offers an excellent corridor for groundhogs to travel along, so kayakers may spot woodchucks along an embankment.
If you’re interested in observing other wildlife that stirs in spring, you might also enjoy learning about when snakes come out in Illinois, another group of animals whose seasonal emergence closely follows warming temperatures. For a broader look at hibernation timing across the region, see our guides on when bears come out of hibernation in Kentucky and when bears come out of hibernation in Indiana.
How to Tell If a Marmot Is Active in Illinois
You may notice signs of groundhog activity before you ever see the animal itself. Learning to read these clues can help you confirm whether a groundhog is actively using an area — and whether it has recently emerged from hibernation.
Burrow entrances with fresh soil
An active den will show a large mound of dirt and stones by the main entrance to the burrow; secondary entrances, which were dug from the inside, generally don’t have a dirt mound by their opening. Fresh, loose soil around an entrance is a strong indicator of recent activity.
Well-worn trails
A well-worn trail from entrance to entrance, or leading to a garden, is a reliable sign of regular use. These paths become more visible in spring as vegetation is still low.
Feeding evidence
Groundhogs will first venture out to assess their environment, looking for signs of danger and the presence of fresh vegetation before fully re-engaging with their surroundings. Clipped grass stems, nibbled clover, and disturbed garden beds near a burrow are all indicators of post-hibernation feeding.
Daytime sightings near the burrow
Woodchucks are diurnal, most active during the day, particularly in the early morning and late afternoon hours. They stay close to their burrows when feeding and typically only stay above ground a couple of hours per day. Seeing a groundhog sitting upright — its characteristic “sentinel” posture — near a burrow entrance is one of the clearest signs of active presence.
Common Mistake: Assuming a burrow is inactive just because no animal is visible. Groundhogs spend most of their time underground even during active months. Check for fresh soil, tracks, and nibbled vegetation rather than relying on direct sightings alone.
Track patterns
Woodchucks have four toes on the front paws and five toes on the back paws. The tracks are spaced about four inches apart when woodchucks are walking and 12 inches apart when they are running. Woodchuck tracks are about 1½ inches long. Look for these in soft soil or mud near burrow entrances after rain.
Comparing activity across seasons can also deepen your understanding. Groundhog behavior in late winter and early spring differs noticeably from summer patterns, when animals are focused on intensive feeding rather than territory-scouting. For a broader sense of how hibernating mammals time their emergence in neighboring states, the guides on bears emerging in Massachusetts and bears emerging in Maryland offer useful seasonal context.
Whether you’re watching from a forest preserve trail, a rural roadside, or your own backyard, Illinois groundhogs follow a reliable seasonal rhythm. The mid-to-late February window is your first opportunity to catch them above ground after a long winter underground — and by March, the state’s fields and forest edges come alive with their steady, purposeful activity once again. Knowing when and where to look makes all the difference.