Post by Jen Berlinghof

Late last summer, I literally watched a groundhog (Marmota monax) fatten up before my eyes. He’d made a burrow in the field outside my office window and frequently visited the rain gardens around the Edward L. Ryerson Welcome Center in Riverwoods, part of the Lake County Forest Preserves in northern Illinois. We watched him scamper back and forth, snipping flower tops here and there, always with a mouth crammed full of flora.

Fast forward to early February, and as I look out across the same field, now dotted with small snow drifts punctuated by tufts of grasses gone tawny, I think about that groundhog curled tight in his burrow and deep in hibernation, oblivious to the hubbub of a day in his honor.

February 2 is about halfway between the winter solstice and the spring equinox. Historically, people have celebrated this seasonal crossroads in many ways. Groundhog Day in the United States is best described as a case of mistaken identity. It stems from a Germanic tradition involving hedgehogs and badgers as weather predictors for farmers. When German settlers arrived in Pennsylvania, they carried on this custom, substituting groundhogs, which were plentiful in the Keystone State.

While groundhogs can’t predict the weather, they do have other notable traits. It seems that we humans can’t quite agree on what to call them. Two common nicknames are woodchuck (which derives from a Native American word, wuchak) and whistle-pig (an homage to the high-pitched squeaks they use to signal danger). Groundhogs are rodents, and in fact, they’re Lake County’s largest squirrel, weighing in at up to 15 pounds. They can be seen swimming and climbing trees to elude predators such as raptors and coyotes (Canis latrans), which threaten to detour them away from their main focuses of food, architecture, and mating.

Except for mating season, groundhogs are solitary and spend the summer and early fall bulking up on a mostly plant-based diet, with some slugs and grubs as occasional ingredients. During this time, they also use their powerful front claws to create complex burrows. Their underground abodes have multiple entrance holes and can stretch up to 50 feet over several levels with numerous chambers. They even have a dedicated restroom chamber.

Once temperatures drop in late fall, groundhogs retreat alone to these palatial homes and begin hibernation. Unlike other animals that merely hunker down for cold bouts in the winter, groundhogs are true hibernators. They oscillate between short periods of arousal and long periods of torpor. In this altered state, groundhogs lose up to a third of their body weight. Their heart rate plunges from 80 to five beats per minute and their body temperature falls from 98 to 38 degrees Fahrenheit, about the same as inside a refrigerator.

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 the females living in their two-to-three-acre territory. It’s more a first date than anything else, but weather forecasting certainly isn’t on the radar for these rodents. The males eventually head back to their own burrows for another round of torpor before they emerge again to mate in early spring.

At the burrow I’ve been keeping tabs on, there are no tracks or signs of this groundhog rendezvous yet. But like the end of winter, whether it’s six weeks longer or not, my groundhog friend’s reemergence is one more thing to look forward to this spring.

Get close to a real groundhog, make some tracks, and test your trivia knowledge at our Groundhog or Woodchuck? Drop In program, February 2, 11 am–4 pm. Learn more about one of Lake County’s few true mammal hibernators. FREE. No registration required. All ages welcome. Meet at the Edward L. Ryerson Welcome Center.