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Spider monkeys hug to reduce group tensions.

Filippo Aureli

Hug It Out, Monkey

We all do it: Give friends and family a peck on the cheek, a quick hug, or maybe even a nose rub to say hello. It's a way of assuring each other that we have no hostile intent, anthropologists say. Now, primatologists report that spider monkeys embrace intensely after a period of separation for exactly the same reason.

Like humans and chimpanzees, spider monkeys (Ateles geoffroyi) live in small groups that split apart to feed or hunt (or shop at Saks) and then rejoin later in the day. For years, researchers have noticed that these monkey reunions are often accompanied by public displays of hugging. "They give a quick call and look intensely at each other, and then briefly wrap each other in their long arms in what's almost a passionate embrace," says Filippo Aureli, a primatologist at Liverpool John Moores University in the U.K. In some cases, the monkeys even curl their tails around one other.

To decipher the social meaning of these embraces, Aureli and primatologist Colleen Schaffner of the University of Chester in the U.K., studied two spider monkey communities on Mexico's Yucatan Peninsula. After analyzing some 195 "fusion events"--the moment when the monkeys got back together--the researchers noticed a distinct pattern. Individuals that embraced upon meeting again seldom behaved aggressively toward each other or the rest of the group. "This is always a time of potential friction and when they're most prone to fight," says Aureli, "because of the limited supply of food or other resources." Hugging is "their way of conflict management," he says. The team reports its findings online this week in Biology Letters.

"It's a valuable study," says Frans de Waal, a primatologist at Emory University in Atlanta, Georgia. "It shows how important greetings are in these fission-fusion societies, including our own."

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