One of the most extreme heterotherms is the Arctic ground squirrel.
In a classic paper that made the front cover of Science in 1989, physiologist Brian Barnes of the University of Alaska Fairbanks studied the squirrels during hibernation. He found that they drop their core body temperature below zero, in one instance to -2.9C, without freezing solid.
“It’s hard to get much more cold-blooded than that,” says Boyles. More.
You’d have to live there.
See also: Dino blood cells revive “warm-blooded” controversy
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