09/14/2026
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The 350 beats per minute dropping to 4 and body temperature falling toward 40 degrees are both well documented, so the infographic's numbers hold up. Here's the caption.
Right now, chipmunks are running one of the most frantic food operations in the backyard, and most people barely notice it happening under their own porch steps. Every trip out means cheeks stuffed to several times the size of the head, hauling acorns, seeds, and nuts down into an underground burrow that can stretch out surprisingly far beneath the soil.
By late September, that burrow's pantry chamber is packed, and the chipmunk starts sleeping right on top of the stash it has spent weeks building. This isn't hibernation in the way most people picture it. Chipmunks don't build up the thick layer of body fat that true hibernators like groundhogs rely on to sleep straight through winter. Instead, they store food because they have to wake up and eat it.
Late October is when the burrow gets sealed off. The chipmunk plugs its entrance with soil and retreats below ground, cutting itself off from the surface world for the season. What happens physiologically after that first hard freeze is genuinely extreme for a small mammal. A chipmunk's resting heart rate normally runs around 350 beats per minute, and once it drops into torpor, that rate can crash to somewhere around 4 beats per minute. Body temperature falls from close to 100 degrees Fahrenheit down toward the temperature of the burrow itself, often into the low 40s.
This is where chipmunks diverge from animals that hibernate continuously. Instead of one long uninterrupted sleep, a chipmunk cycles in and out of torpor throughout the winter, typically every few days. It wakes up, its heart rate and body temperature climb back to normal, and it eats directly from the food pile it stashed back in the fall before dropping back into torpor again. That's the entire strategy: no fat reserves to slowly burn through, just a buried pantry and a body built to shut down almost completely between meals.
It's a useful reminder that a quiet pile of leaves by the foundation or a small hole near the base of a step isn't nothing. There's very likely an entire winter survival system running underneath it, built on months of frantic collecting and a heart rate that can swing from 350 beats a minute to nearly stopped, over and over, until spring finally arrives. ๐ฟ๏ธ๐