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 ...
