Chimpanzees and Bonobos Use Touch to Reassure Before Food Stress, Study Finds

Chimpanzees and bonobos engage in touching, embracing and kissing to reassure one another before stressful feeding situations, researchers at Durham University reported. The team observed the apes at two sanctuaries in the Democratic Republic of Congo and Zambia during the five minutes before peanuts were distributed, an experiment designed to mimic natural feeding conflicts in the wild.

Individuals that initiated or received reassuring contact were more likely to reach the food and eat alongside others without conflict.

More tolerant groups displayed higher rates of such touch, including sequences in which multiple apes formed what the researchers called reassurance trains by embracing one another in succession. Chimpanzees, despite their reputation for aggression, also performed close-contact gestures such as placing fingers in one another's mouths.

"Before stressful events, they come together, they reassure each other, they touch each other, they hug each other," said Prof Zanna Clay.

"Comparing bonobos and chimpanzees — our two closest relatives — offers fascinating insight into the evolutionary roots of social behaviour and how they, and we, manage tension, competition and cooperation," said Dr Jake Brooker. He noted that social touch ranks among the oldest forms of communication and likely predated language.

The researchers concluded that the use of touch to build trust and cooperation may date back at least seven million years, before humans, chimpanzees and bonobos diverged from a common ancestor.

The findings appear in the journal Proceedings of the Royal Society B: Biological Sciences.