Heart-Healthy Hibernators

Overwintering ground squirrels survive fluctuations in body temperature that would cause cardiac arrest in nonhibernators.

Written byJef Akst

| 4 min read

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CURLED UP FOR A NAP: A thirteen-lined ground squirrel assumes a posture typical of hibernation in the hands of University of Minnesota Duluth researcher Matthew Andrews.JAMES BJORK

Every fall, thirteen-lined ground squirrels (Ictidomys tridecemlineatus) in the United States retreat to their underground burrows for a long winter’s nap. They curl up in a tight ball and enter a state of torpor, where their body temperature drops to just a few degrees Celsius, their metabolism plummets by up to 95 percent, and their hearts beat just 3 to 10 times per minute. “It looks like they are dead,” says electrophysiologist Alexey Glukhov of the University of Wisconsin School of Medicine and Public Health. “When you touch them, they are cold and they are rigid.”

But like all hibernating animals, every week or two the squirrels stir from their slumber. Sometimes they’ll move around; other times they’ll simply stay in a tight ball. Upon ...

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Meet the Author

Jef Akst
Jef (an unusual nickname for Jennifer) got her master’s degree from Indiana University in April 2009 studying the mating behavior of seahorses. After four years of diving off the Gulf Coast of Tampa and performing behavioral experiments at the Tennessee Aquarium in Chattanooga, she left research to pursue a career in science writing. As The Scientist's managing editor, Jef edited features and oversaw the production of the TS Digest and quarterly print magazine. In 2022, her feature on uterus transplantation earned first place in the trade category of the Awards for Excellence in Health Care Journalism. She is a member of the National Association of Science Writers.
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