Happy Groundhog Day!

Every year on February 2, we celebrate Groundhog Day. But what are groundhogs, and why do they have their own holiday?

Groundhogs (a.k.a. woodchucks) are medium-sized rodents, typically weighing 7–10 pounds. Common through much of the eastern United States and Canada, they have a brushy tail, mottled brown fur and short legs, which give their movement a characteristic “waddle.” Groundhogs are active during the day and prefer to eat vegetation such as clover, dandelions, alfalfa and garden crops. They dig burrows in which they rest, raise young and hide out from predators. These food preferences and burrowing behavior can often cause conflict with humans.

When winter comes, groundhogs hibernate in their underground burrows, blocking the entrance with leaves. During this period (typically November–February in Illinois), a groundhog’s body temperature drops to that of the burrow (around 40–50 degrees) and their heart beats just a few times per minute. Hibernation may sound easy, but groundhogs lose approximately 30 percent of their body weight! Once they emerge, they have to spend most of their time feeding to prepare for next year.

Lincoln Park Zoo’s Urban Wildlife Institute is currently monitoring four groundhogs in the Chicago area. We’re studying them to better understand the outcomes of relocating “nuisance” groundhogs. Relocation is often used to manage wildlife conflict with humans, but we know relatively little about what happens when animals are released. What risks do they face in their new locations? How do their movements compare to groundhogs that aren’t relocated? Do they stay at the release sites and find new territories or do they attempt to return home? By tracking them with radio transmitters, we plan to monitor around 50 groundhogs over two years to answer these questions.

So research aside, what is Groundhog Day? Groundhog Day originates in Europe, where farmers predicted the length of winter based on the emergence of burrowing animals such as badgers and hedgehogs. Europeans brought this tradition to North America, using groundhogs as the local burrowing mammals.

As the tradition goes, if it’s a clear day the groundhog will see its shadow and winter will continue for six more weeks. But if the weather is overcast, spring is right around the corner! Unfortunately for the tradition, February 2 is a little early for groundhogs to emerge from hibernation in Illinois. But we’ll be monitoring our study animals that day anyway and excitedly anticipating their future return!

Liza Lehrer

Liza Lehrer, M.S., is a research coordinator in Lincoln Park Zoo's Urban Wildlife Institute.

Groundhog Field Update One
Zoo scientists Liza Lehrer and Julia Kilgour are checking in with the groundhogs they track for a project studying the outcomes of wildlife relocation. “Looks like groundhog number one has not emerged yet,” Liza reports. “Groundhogs cover their burrow entrances with leaves while they are hibernating.“

Groundhog Field Update Two
“Groundhog two is still hibernating!” says Liza. “His burrow entrance is covered with snow and there’s no sign of tracks. Burrow entrances are often under fallen trees or rocks that offer protection and soft soil for digging.”

Groundhog Field Update Three
How do zoo scientists Liza Lehrer and Julia Kilgour find the groundhogs they’re tracking for their project? “We're able to find the groundhogs using radiotelemetry,” says Liza. “Radio transmitters emit a signal that we can pick up using an antenna and receiver.”

Groundhog Field Update Four
“Looks like there’s some activity around this groundhog’s burrow entrance,” says Liza. “The entrance appears to be open. However, the radio signal tells us he’s still hibernating. We’ll be monitoring the groundhogs closely in coming weeks to find out when they emerge and start moving around again!”


Thanks for monitoring these fantastic little rodents! Where can I donate funds to this cause to help these little wood chuckers?

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