For animals that hibernate, making it to spring is no small feat. By the time they emerge, hibernating animals are often sleep-deprived: Most expend huge bursts of energy to arouse themselves occasionally in the winter so their body temperatures don’t dip too low.
Hibernation can last anywhere from a period of days to weeks to even months, depending on the species. Some animals, like groundhogs, hibernate for as long as 150 days, according to the National Wildlife Federation.
Though there’s no pinpointing the day hibernation ends, the timing in which wildlife emerge from their sleep can be predicted to an extent. Most animals stop hibernating during the spring because that’s when the days get longer and temperatures rise, meaning more food sources are available.