Groundhogs do hibernate. The hibernation period for groundhogs typically starts no later than sometime in November, depending on when the cold weather commences. Groundhogs typically become active again as early as February.
Depending on the severity of winter, some groundhogs may only be in hibernation for about two months, but these animals have the ability to sustain for up to five months. When groundhogs are active they have a heart rate of up to 100 beats per minute, but in hibernation it decreases to fewer than 10 beats per minute. Groundhogs have a similar body temperature to humans when active, around 98 degrees Fahrenheit, but their body temperature is less than half of that in hibernation.