What are the reasons why groundhogs hibernate?

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Hibernation is a state of slowed metabolic rate that allows an animal to live off of stored fat for long periods of time. While in hibernation mode, and animal’s body temperature drops and most bodily functions are significantly slowed. Hibernation allows an animal to live through periods of extreme cold when food supplies are few or nonexistent. Groundhogs, unlike bears, enter true hibernation, and the core temperature of a groundhog can get below thirty two degrees Fahrenheit! This cold temperature cannot be held indefinitely, and so every hibernating animal wakes up periodically to move and reestablish body temperature. It used to be assumed that an animal’s metabolism decrease was due to the fact that body temperature was the first function to lessen during hibernation. Scientists recently discovered it is the slowing of the metabolism that decreases the temperature and not the other way around. This discovery proved that hibernation was an involuntary, internal mechanism and not one induced by the decrease in environmental temperatures.



Groundhogs are mostly herbivorous creatures, though they will eat insects and other arthropods from time to time. Because of this vegetation-dependent diet, a groundhog would find it increasingly difficult to find enough food to last through a long winter. To make it sensible to remain active during periods of poor nutrition, an animal needs to take in at least as many calories as it uses up in day to day activities. A groundhog is a rodent, and therefore needs to chew in order to keep its teeth at a manageable length. Without enough nutrient dense food to chew, the groundhog would operate at an energy deficit and ultimately die of starvation.

In order to make it through a hibernation state, a groundhog starts to eat a surplus of food in late summer, early fall. Fall is an opportune time for a groundhog to store up fat. Apples, acorns, walnuts, and other protein-rich, high calorie foods are available. Alfalfa, one of the staples of many groundhog diets, is at its peak in late summer, and provides a nutrient dense food source. Studies have shown that groundhogs with access to alfalfa can grow to be a third as large as groundhogs without the leafy resource. Animals with the widest variety of food sources can make it through the longest winters.

Interestingly enough, some big groundhogs will enter the hibernation state and never wake up. This strange death is not a result of starvation, but could be linked to the low body temperature or the nutritional health of the animal. Groundhogs that awaken early in the spring have that much more time to build up fat stores for next year’s winter. Some experts believe that disease also plays a part in groundhog deaths while in hibernation. If a body is already debilitated by an illness, any drop in body temperature may not be able to maintain enough energy for life support. Whatever the reason, young groundhogs seem to be most affected by this strange issue as well as groundhogs that wake up in late in the spring season.

Many mammals that live in winter climates hibernate or go through a form of hibernation. Sleeping the cold, dark winter months away instead of foraging for scraps of food day after day, might not be such a bad idea. Unlike deer, which are left to face the elements all year long, groundhogs will hunker down in their protected burrows—probably under your deck or shed—and sleep the frigid time away. You may wonder why all mammals in cold climates don’t hibernate. Some grazing animals, for example, need to eat and move constantly to maintain the health of their organs. Horses are unable to lie down for long periods of time without causing serious damage to internal functions, and for this reason, hibernation would be impractical.

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Here is are example emails that I received regarding groundhog control problem:

Hello, i came across your website after i had a very unusual encounter with a groundhog. I just moved to Pennsylvania and i live around a lot of open land. My car (a Honda CRV) is always parked outside on the driveway. Today i had just walked out of my garage and saw a Groundhog under my car and I love animals so of course what do i do, i stand there n watch it instead of scare it away! i was so excited at first until i saw it climb up into my car! i tried tapping the outside of my car to scare him loose. when that didn't work i opened the hood of my car. i saw it laying under the engine somewhere. i tried blowing on it but that didn't work. so finally i called an animal control number i found in the phone book and i asked for suggestions. the man told me to pour water on it. so i grabbed a cup n splashed it with water. He got out after that happened but even after he was still hanging around the bottom of my car. he wasn't too scarred to leave. at one point he even got back up onto my tire while i was right near by. Now maybe it was because he was scarred and he just wanted to be sheltered but I'm still concerned its because he's a little too comfortable there! (LOL) I'm nervous he will come back. is there any suggestions or tips you might have to either detour or prevent the critter from coming back into my car?! if so i would GREATLY appreciate it. I'm just scarred one day I'm going to get into my car to go somewhere and hurt him or run him over. also i wouldn't be too thrilled if he chewed or gnawed any wires. thank you very much! Susan

Hello, my name is Lori and I am sending a message regarding a woodchuck living at my parents house. He has apparently made a home underneath their shed in the backyard. But my mother is not happy about his choice in eating her flowers. We do have a trap and that we could use to transport him to another area, but I am concerned about the possibility of young ones. Can you tell me how to find out if there are any young? And what can I put in the trap in order to catch him/her? I want to do it the best possible way for the groundhog. I don't believe in hurting or stressing any animal. Can you tell me the best thing to do is? Thanks for your help. Lori

Read about Groundhog Under My Shed, Deck, or House or email me with questions about hibernating groundhogs.