Happy Groundhog Day! Every February 2, we look to the meteorological expertise of these burrowing mammals to learn about the seasonal forecast: If the groundhog sees his shadow due to sunny weather, he will retreat into his den for another six weeks of winter. If the sky is overcast and he doesn’t see his shadow, then the winter will end early.
Despite the lore surrounding groundhogs passed on from the Pennsylvania dutch, these furry ground squirrels do not typically offer the most reliable of weather forecasts. This legend may have first sprung up because groundhogs can, in fact, be seen emerging from a deep slumber in their cozy dens to poke their heads out into the early February cold. Male groundhogs will wake up around this time and leave their own burrows in search of a den to share with a nearby female groundhog. They will hibernate together for the rest of the winter months in her burrow, and when they both wake up in the spring they will already be well-acquainted with one another.
Groundhogs are one of only three types of animals in Maine that spend the cold and snowy winter months hibernating. A few species of bats and the meadow jumping mouse join the groundhog in making up Maine’s team of “true” hibernators. This means that when the shorter days and hormones begin to signal to these animals that it’s time to hunker down for the winter and go to sleep, they mean business. Touching or moving these animals will not be enough to wake them up once they begin their hibernation.
True hibernators slow down their metabolisms and decrease their body temperatures drastically. They spend much of the fall foraging for food to build up their fat stores so that when they begin hibernating, they will only need to wake up every so often to eat some of their food stash and raise their body temperature before going back to sleep. A groundhog may eat enough in the fall that its abdomen is covered in an inch of fat, and its body temperature can drop from about 99 degrees to 37 degrees Fahrenheit. Humans, on the other hand, can enter a state of hypothermia from a body temperature drop of just three degrees. During hibernation, a groundhog’s heart rate can drop from 80 beats per minute to 5, and their breathing slows from 16 breaths per minute to 2.
This coma-like state is what separates true hibernators from other animals who also slow down and spend much of the winter sleeping. Many of the warm-blooded wild animals who seem to disappear in the winter do not hibernate, but actually enter a lighter slumber known as torpor. Black bears have quite a reputation for being able to sleep all winter long, but they can be roused quite easily if disturbed. It is wise to remember that a bear can certainly wake up if poked! A bear will decrease his body temperature, metabolism, breathing rate and heart rate in the cold months, but not as drastically as the true hibernators. A black bear’s body temperature only drops by about ten degrees, compared to the 62 degree temperature drop experienced by groundhogs. Although black bears are not true hibernators, their strategies for enduring the winter are certainly impressive: bears do not need to eat, drink, or pass waste for 100 days, and can actually convert their body’s waste materials to help maintain their organ and muscle tissue while sleeping the winter away.
Groundhog Day is an excellent time to stop and appreciate the amazing adaptations and survival strategies of the animals doing their best to make it through the winter in Maine–just like us!
If you are interested in learning more about the natural history of these animals or in meeting our resident non-releasable groundhog (and the star of these pictures), Clover, you can visit our website to learn more about the programs offered by the Traveling Natural History Program: http://tnhp.chewonki.org.