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