Groundhog Facts

The groundhog secretes its territorial marking scent through three nipple like anal glands.
The female groundhog has one litter of usually three to five young per year.
Groundhog live from 6 to 10 years.
The "Gopher" in the Caddyshack movies is not actually a gopher - it is a groundhog.
The groundhog will climb trees in search of food.
The groundhog has been observed swimming.
The groundhog has earned its nickname "whistle-pig" due to its tendency to produce a high-pitched whistle when frightened which it will often times mix with both barking and chattering noises.
All groundhogs hibernate through the winter: systematically waking from their sleep in the spring by means of some sort of internal alarm clock that is not generally understood.
Groundhogs will travel a great distance to a food source.
The groundhog does not "chuck wood" of any kind.
A burrow and den system will be used for many seasons. The groundhog will keep the nesting area of the den clean and change bedding material regularly.

Acknowledgment:

Rene M. Bollengier. Jr., 1994. Woodchucks: Prevention and control of wildlife damage. Assistant Regional Director (retired). USDA-APHIS Animal Damage Control.