What goes on in a groundhog burrow?
Well, not much in the winter. You might say they take a long nap. Groundhogs go into deep hibernation, greatly reducing their metabolic rate and body temperature. They hibernate in the deepest portion of the burrow where it is below frost line. That means their body temperature can drop as low as 39-40 degrees Farenheit. Like humans, their internal clock is affected by annual changes in the amount of daylight. Hormonal responses to cyclic changes in production of melatonin, a sleep-related hormone, signal them to wake up!
