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Adult bonobos cry like babies to elicit the support of others

Bonobos (Pan paniscus) are our closest living primate relatives and share more than 98 percent of their DNA with us. They are also among the most vocal of the great apes, using around 15 different call types to communicate particular emotional states, such as screaming, threat barks, greetings and alarm calls. For a long time, it was thought that great apes had no control over their emotional expressions but made them instinctively in response to the specific emotional state.

However, a new study of captive bonobos in the Democratic Republic of Congo has revealed an altogether different situation. Psychologists at Durham University have found that adult bonobos use “baby-like” distress calls to curry favor with group members after a conflict. The calls are often accompanied by other behavior typical of baby bonobos, such as pouting, whimpering and throwing tantrums. 

The researchers suggest that these calls are used strategically to reduce the chances of another conflict with the opponent, and to elicit comforting behavior from others in the group. The adult bonobos usually stop signaling their distress in this way once they receive support from other adults, whereas immature bonobos will continue to call even after they have been consoled. 

The study, published in the Philosophical Transactions of the Royal Society B, Biological Sciences, was based on research carried out on two bonobo groups (over 40 individuals) at the Lola ya Bonobo Sanctuary in Kinshasa (Democratic Republic of Congo), the world’s only bonobo sanctuary. 

The researchers examined how bonobo victims communicate about their distress after a fight, and whether these signals affect the responses of bonobo bystanders. The findings indicated that adult bonobos were less likely to be re-attacked after a conflict with an opponent if they displayed behavior and made calls typical of baby bonobos. They were also more likely to elicit a comforting response from the bystanders.

The analysis also showed that a bonobo is sensitive to who is present in the audience when it is attacked, and will display more signals in general if more bonobos in the social audience are nearby. This suggests bonobos adapt their communication signals depending on which individuals are in the close vicinity. The results thus indicate that expressions of emotion are not simply instinctual read-outs of internal states but can be used in flexible and strategic ways to manipulate others and purse social goals. 

“Bonobos are highly sensitive to social situations and who is surrounding them. They have rich emotional lives and are able to communicate their emotional states in flexible ways to influence their group members,” said study lead author Dr. Raphaela Heesen

“In using specifically “baby-like” signals, bonobos might increase their chances to be consoled by others and alleviate their own stress level following aggressive attacks. Our research shows that emotions and their expression do not only play a role in the regulation of social life in our own species, but also in our closest living primate relatives.”

“The act of comforting a victim in distress has long been considered a form of empathy that is initiated by the bystander. However, our study reveals that the victim’s own signals may be used strategically to shaping these responses,” said study senior author Dr Zanna Clay.

“By producing signals that make them seem more like infants, bonobo victims can promote the chances of receiving comfort from others. This highlights the important role that communication plays in shaping empathic responding.”

The researchers thus emphasize that bonobos have flexible ways of communicating their emotions, just like humans. The study sheds light on understanding the emotional life of these animals with a focus on the potential evolutionary origins of the communication of emotions.

By Alison Bosman, Staff Writer

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