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Strange (and Sweet) Primate Behaviors

Posted by Richard Conniff on October 22, 2013

A bonobo consoles a distraught pal (Photo: Clay & DeWaal)

A bonobo consoles a distraught pal (Photo: Clay & DeWaal)

One of the persistent myths about the natural world is that animals live in a constant state of aggression, confrontation, and even open combat.  But even relatively brutal chimpanzees spend only about five percent of their day in aggressive encounters–and 20 percent grooming social allies.

The truth is that the social and emotional lives of other primates are in many ways a lot like our own, and two new studies add to the growing evidence.  In the first, published in Evolution and Human Behavior, the researchers found that chimpanzees, like humans, typically form friendships with individuals who have similar personalities. Researchers Jorg J. M. Massen and Sonja E. Koski spent hundreds of hours observing chimpanzee troops at two European zoos, paying particular attention to individuals who liked to sit together.  These friends turned out to be similar in sociability based on how much time they spent grooming, and whether they liked to hang out in a crowd, or off on the periphery.  They also resembled each other in boldness—that is, the willingness to mob an apparent threat, like an artificial snake.

That suggests why friendships may matter as much to chimps as to humans: They make it more likely that individuals will find a mate, reproduce, keep the kids alive, and stay well themselves.  Friends also support each other in conflicts.  For chimps, as for humans, having friends is natural and necessary. These are social creatures, never meant to live in isolation.

The other study, just out in Proceedings of the National Academy of Sciences, looks at the emotional lives of bonobos, a separate chimp species thought to be even more closely related to humans. Researchers from Emory University studied bonobos rescued from the bushmeat and pet trades, at a forested sanctuary on the outskirts of Kinshasa in the Democratic Republic of Congo.  The emotional life of non-human primates is “still rather a taboo subject in animal behavior,” co-author Zanna Clay told TakePart, in an email.  Old School researchers suspect it as a form of anthropomorphism—that is, projecting human feelings onto animals.

But Clay and co-author Frans de Waal became interested in the topic when they noticed striking differences in how individuals behaved.  “Some juveniles were real social stars, they were always dashing about keen to play and groom with everyone,” said Clay. She was particularly impressed by Pole (pronounced Po-lay), ”a brave and very sociable young male, with lots of friends and lots of energy.”

Despite the oversexed reputation of bonobos, their lives are not a perpetual love-in.  Conflict is normal, and the celebrated “bonobo handshake” can alternate at times with the bonobo slap in the face.  When another bonobo “gave him a whack,” said Clay, Pole shrugged it off.  When the same thing happened to less resilient individuals, though, they often worked themselves into a screaming fit.  That caused other bonobos to move away.

Pole moved closer instead, even if the victim was “still too worked up to accept the comforting touch,” said Clay.  He risked getting whacked again.  But he often stuck around to hold the victim in a comforting embrace for minutes afterwards[RC3] . Pole was clearly a master at regulating emotional response to distress, both his own and that of other bonobos.  And that fit the overall pattern: “It seemed to be that the best consolers were also the best ones at regulating social and emotional events overall.”

The two researchers realized they were witnessing a phenomenon already well documented in human children:  Individuals who are better at regulating their own internal emotions are also better at empathizing with others.

As in humans, what happened to the individual early in life also made a critical difference. Individuals who had lost their mothers “at the hands of illegal bush-meat hunters in the forest” suffered a sharp emotional setback.  The Lola ya Bonobo Sanctuary  provided a loving caretaker to help rehabilitate each orphan. But “there are still some things that only the actual mother is able to provide,” said Clay. These orphans were less likely to recovery quickly from stress or console others, and they tended to be more anxious.  For instance, they scratched themselves more often, a common means of distracting themselves from stress.

But the researchers also found cause for hope in the way the orphans made an effort at re-building normal social lives.  “Our results,” Clay and de Waal write, “demonstrate the striking resilience of these bonobo orphans.  The fact that they were able at all to reconcile conflicts, console others, and engage in … play and grooming, suggests that they were managing reasonably in their social world.”

Clay is now deep in the forests of the Congo beginning research to find out if the same emotional patterns also play out in the lives of bonobos in the wild.

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