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Seeing Their Shadow in City Lights

Ah, the groundhog. Largest, and arguably most adorable, form of squirrel in our country.

Tunneling torment.

‘Clairvoyant' climatologist.

Metropolitan maverick?

Just in time for Groundhog Day, researchers Robert Schooley and Liza Watson of the University of Illinois have determined what many green thumb gardeners may already know: groundhogs favor city life.

For two years, Watson, a wildlife ecology graduate student, observed 41 rural or urban groundhogs to determine the impact of urban landscapes on the animals' behavior, movements, and survival rates. Her method was a classic stakeout: because groundhogs aren't disturbed by stationary vehicles, she'd track their location via radio tags and observe their activities from 30 meters away in the passenger seat of a truck.

Watson recognized a distinct behavioral difference between the rural and urban groundhogs. Once habituated to humans and the urban landscape, groundhogs, which rely on sight rather than smell to detect predators, spend less time scanning for attackers and more time foraging for food.

"If you're standing up on your hind legs all the time looking for predators, you can't be feeding, and in order to survive hibernation, they need to spend as much time as possible feeding during the active season," she said.

This sense of security the urban woodchucks have been lulled into is likely due to the fact they have fewer predators than their rural counterparts. Urban landscapes are hostile ecosystems for coyotes, wolves, and other large predators, so groundhogs in these areas are less likely to be eaten. (Although I'd bet dodging SUVs and minivans is another matter...)

As an added bonus, food is readily available in the city. While urban and suburban areas restrict the size of home ranges, groundhogs have an abundant supply of grasses, ferns, bushes, and homegrown vegetables to pick from. Considering an adult groundhog is capable of eating a pound and a half of plant material a day, such ample supply of nourishment in private gardens and public parks is no doubt appealing to these oversized rodents.

With more food in their belly, a groundhog is less likely to awake mid-hibernation with hunger pains only to find snow-covered ground and leafless shrubs. The researchers found that deceased rural groundhogs not killed by predators (a majority) appeared to have died from starvation during hibernation, when an adult typically loses 35 to 40 percent of their body weight. In such a situation, they'd really be grateful to wake up and see no shadow.

Who knows, maybe next year we'll be getting weather predictions from Philadelphia Phil.