Every February 2, residents of Punxsutawney, Pennsylvania awaken a groundhog from its winter's nap. According to lore, if the groundhog casts a shadow, then six more weeks of winter lie ahead. If not, then residents can look forward to an early spring. This Groundhog Day tradition has roots in the behavior of real groundhogs, which briefly emerge from hibernation in late winter before returning to their burrows for the rest of the season. Clear text...