November 3, 2003

Risky diddling bonds baboons

Male apes share intense greetings only with close friends.

by John Whitfield
Nature News

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Want to show someone you really like them? Slap them in the face.

That, at least, seems to be the message of baboon salutations. The closer the social bond between two animals, the more intrusive and risky the greeting when they meet. For male Guinea baboons (Papio papio), this involves ritualized fiddling with each other's genitals.

Baboons impose on each other to demonstrate and test the strength of their relationship, says Jessica Whitham of the University of Chicago. The hazards involved in such intimacy mean that only truly trusting apes will get up close and personal, she says.

"Male baboons have a high potential for aggression. One bite to the genitalia with sharp canines can effectively end a male's mating career," says Whitham. She and her colleagues spent nearly 200 hours over six months watching a colony of captive baboons at Chicago's Brookfield Zoo.

Penis and scrotum diddling is the culmination of a complex greeting ritual that begins with face pulling and progresses through rump presentation and embracing.

The baboons that were more likely to embrace or exchange diddles also spent a lot of time together, and groomed one another frequently1. Aggressive interactions led to frostier greetings.

Genital fiddling is unique to guinea baboons, but other primates invade each other's space in similarly challenging ways. White-faced capuchin monkeys, for example, stick their fingers up each other's noses in greeting.

But we shouldn't look for a human equivalent, says Whitham: "Most human greetings do not carry the same potential costs as those exchanged between adult male baboons."

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