Groundhogs are true hibernators, meaning they sleep through the winter regardless of conditions.
(Cephas / Wikimedia Commons)
When winter descends on Indiana, furry, scaly and slimy creatures alike hunker down for hibernation. However, warmer and shorter winters are causing some species to sleep later – or not at all.
Hibernation is a complicated process governed by different conditions across plant and animal species. Some trees, for example, take their cues to grow leaves and fruit by day length whereas others do so based on temperature.
Under historic conditions, these cues line up in predictable ways. But with the climate changing, species can’t rely on those seasonal patterns.
Indiana University biology professor and mammal expert David Polly said that changes to plant hibernation can have far-reaching effects on ecosystems.
“If their cycles get off sync, then the whole food web becomes involved in some of that complexity,” Polly said. “That's probably what worries climate change biologists the most.”
Greg Demas is a biology professor who studies animal timing at IU. He said that hibernation for most animals is governed by “hibernation genes” triggered by certain conditions.
Indiana species like bats and chipmunks are facultative hibernators; they hibernate under the right conditions but stay awake if those conditions aren’t met.
“There is actually evidence that some animals are coming out of winter hibernation earlier, and therefore the food may not be available when they're coming out of hibernation in early spring,” Demas said. “Other species, like chipmunks, aren't even going into hibernation, and it's affecting their survival.”
Groundhogs are Indiana’s only obligate hibernators, meaning they sleep for several months each winter regardless of conditions.
Hibernation is physically taxing for groundhogs – their body temperature falls to just above freezing and their heart rate declines to four to 10 beats per minute. By the time groundhogs emerge, they’ve lost around half of their bodyweight.
Polly said early springs could be difficult for groundhogs.
“Normally they'd be coming out before a lot of other populations have gotten going in the spring, and they’d have a chance to beef up again,” he said. “Whereas now everything may be going on as normal, and other species competing for the food or predators are more numerous or whatever by that time. So, it could be detrimental to them depending on the situation.”
Chipmunks and groundhogs are not endangered in Indiana, and their populations remain stable (for some bat species, it’s a different story). Still, the full impact of changing sleep patterns on ecosystems may not be known for some time.
