A new study finds that cold tolerance might be linked to changes in a specific cold-sensing protein in the sensory nerve cells of the ground squirrels and another hibernator. The altered protein may be an adaptation that helps the animals drift into hibernation.

In experiments, mice, which don’t hibernate, strongly preferred to hang out on a hot plate that was 30° Celsius versus one that was cooler. However, Syrian hamsters (Mesocricetus auratus) and the ground squirrels (Ictidomys tridecemlineatus) didn’t seem to notice the chill until plate temperatures dipped below 10° Celsius, notes study coauthor Elena Gracheva, a neurophysiologist at Yale University.