Here's how to think about it:
* Groundhogs hibernate for around 4-6 months: This is the time they spend asleep in their burrows, with their metabolic rate slowing down drastically.
* During hibernation, their biological clock slows down: They don't experience time in the same way as when they are awake.
* The length of "winter" for a groundhog is the duration of their hibernation: While they might wake up briefly on warmer days, they spend the majority of the cold season asleep.
So, while the winter season for humans might last several months, for a groundhog, it's effectively the length of their hibernation period.