Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Despite advances in meteorological technology, we still keep a close eye on a rodent’s burrow every February 2 for a weather forecast. While groundhogs—also called woodchucks—have been associated with the end of winter and beginning of spring for centuries, there’s more to know about our rodent friends than their amateur Al Roker’ing.  No pee or poop Unlike bears, groundhogs are true hibernators. During hibernation, they don’t eat and rely on the fat stores they have built up and go into a deep and full sleep during the winter.  “They don’t wake up and walk around, go to the bathroom or anything like that,” Karen McDonald, STEM program coordinator at the Smithsonian Environmental Research Center in Maryland tells Popular Science. “The waste is actually being recycled in their body.” When they are awake in the spring, summer, and fall, groundhogs use restroom chambers in their burrows to limit odors and fecal contamination in their main chambers. They also reduce their …