Kissing and Dissing Cousins

Among Belding's ground squirrels, kin get special treatment

• Laura Tangley
• Aug 01, 2002

It's the classic case of self-sacrifice for one's kin. When a predator approaches, a female Belding's ground squirrel rears up on her hind legs to bark a warning to her mother, sisters and daughters, risking her own life to protect theirs. She does not give the warning, though, if only strangers--or even aunts and cousins--are present.

In Darwinian terms, the squirrel's behavior makes sense. By saving the lives of family members that share half her genes (mothers, daughters and sisters), she leaves behind a generous genetic legacy even if she dies herself. That would not hold true for cousins (nor for strangers, of course), yet biologists have long wondered whether the rodents are simply unable to recognize their more distant relatives as kin.

In a recent study, Jill Mateo of Cornell University discovered that female Belding's squirrels can in fact identify their cousins and distinguish them from strangers. They do this by sniffing glands located near the other animals' mouths, a behavior that looks like kissing. "It's as if these squirrels are reading DNA fingerprints and drawing the family tree with their noses," says Mateo.