Within three months these young hogs can usually take care of themselves completely. They communicate with one another through a low bark and a high pitched whistle. One less common name for the groundhog is whistle pig. Groundhogs are known to fight among themselves, and also with natural enemies to defend their lives. Another means for the groundhog to survive is through hibernation.
Hibernation begins in the fall.
By this time of year the animal has gained quite a bit of weight in preparation for a deep winter sleep. Dependent on the outside temperatures, sometime around October they will enter their burrows where they remain for the next four or five months. During that time they are almost completely inactive. Their normal body temperature dips to about 38 degrees, while the heart rate drops from about 80 to 4-5 beats per minute. 2 Most of the tradition that surrounds Groundhog Day is derived from the groundhog's awakening after hibernation.