By Susan Milius
SNOWBIRD, UTAH — Wake up and smell the armpit.
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That’s basically what Belding’s ground squirrels do in spring when hibernation has wiped out their memory of their society’s smells, says Jill Mateo of the University of Chicago. Using their own body odors as reference points, the ground squirrels figure out anew each year who’s kin and who’s not.
Self-sniffing as a guide to kinship has earned the nickname “armpit effect.” Biologists have theorized that plenty of animal species rely on their armpits when they do favors for kin or avoid relatives as mates. “There’s tantalizing evidence for the armpit effect in people,” Mateo says, but ruling out other possible explanations has been tricky in any species.