The Love of a Stranger – Bonobos Care About Others

For the last month we have been reminded that Christmas is a time for sharing. But at the start of a new year how many of us carry this sentiment through the rest of the calendar months and how many of us would put a stranger before someone we know?

Our natural tendency if we are to share is to choose a person we known first. But bonobos  – also known as the “love monkey” (they are in fact great apes from the Congo, not monkeys) – nicknamed because they use sex as a currency for practically everything: grooming, feeding, reconciling conflicts; prefer to share with strangers than acquaintances.

According to new research, a bonobo (Pan paniscus) will invite a stranger to share a snack while leaving an acquaintance watching helplessly from behind a barrier. And they apparently value that more than maintaining the friendships they already have.

Professor of evolutionary anthropology at Duke University, Brian Hare who was involved in the study said: “It seems kind of crazy to us, but bonobos prefer to share with strangers. They’re trying to extend their social network.”

In order to measure this willingness to share Hare and graduate student Jingzhi Tan ran a series of experiments with bonobos living in the Lola ya Bonobo sanctuary in Kinshasa, Democratic Republic of Congo. The experiments involved piles of food and enclosures that the test subjects were able to unlock and open.

In the first series of experiments, a pile of food was placed in a central enclosure flanked by two enclosures, each of them holding another animal. The test subject had the knowledge and ability to open a door to either of the other chambers, or both. On one side was a bonobo they knew from their group (not necessarily a friend or family member) and in the other was a bonobo they had never really met, but had only seen at a distance.

When entering the chamber with the food, the test subjects could easily just sit down and consume it all themselves, or they could let in one or both of the other animals to share.

Nine of the 14 animals who went through this test released the stranger first. Two preferred their group mates. Three showed no particular preference in repeated trials. The third animal was often let in on the treat as well, but more often it was the stranger, not the test subject, who opened the door for them.

I’ve never had the privilege to see bonobos in action but it’s on a bucket list which is headed ‘Things to See/Do in Congo’. They are said to be the most similar to humans than chimps. In 51 trials of the experiment, there was never any aggression shown, although there was quite a bit of typical bonobo genital rubbing between the strangers.

To isolate how much motivation the animals receive from social interaction, the researchers ran a second set of experiments in which the subject animal wouldn’t receive any social contact with another animal. In the first of these experiments, the subjects couldn’t get any food for themselves regardless of whether they chose to open the door to allow the other animal to get some food. Nine out of ten animals shared with the stranger at least once.

In the final experiment without social contact, the subject animal was given access to the food in such a way that opening the door to share with the other animal would cost them some food. But they still wouldn’t have any social contact as a reward. In this instance, the animals chose not to share. “If they’re not going to see a social benefit, they won’t share,” Hare said.

“They care about others,” Hare added, but only in a sort of selfish way. “They’ll share when it’s a low-cost/low-benefit kind of situation. But when it’s a no-benefit situation, they won’t share. That’s different from a human playing the dictator game. You really have to care about others to give anonymously.”

The findings, which Hare calls “one of the crazier things we’ve found” in more than a decade of bonobo research, form yet another distinction between bonobos and chimpanzees, our two closest relatives. “Chimps can’t do these tests, they’d be all over each other.”

Bonobos share with strangers   (Tan and  Hare  2013) PLOS ONE