A new study suggests that bonobos show responsibility towards preparation partners similar to those of people working together on a task.
Until now, research has only shown that humans can work together towards a common goal that is presumed to require round-trip exchanges and the assessment of being bound to a partner (SN: 10/5/09).
Primate biologist Raphaela Heesen of the University of Durham in England and colleagues studied 15 of the endangered great apes in a French zoo. Investigators interrupted 85 cases of social grooming, in which one monkey cleaned the skin of another and 26 cases of personal grooming or solitary play.
The interruptions consisted of a guard calling a bonobo in a grooming pair to attend a food reward or a guard quickly opening and closing a sliding door to an indoor enclosure, which usually signaled time to eat and attracted the two bonobos.
Social preparers resumed, on average, 80 percent of the time after food rewards and 83 percent of the time after sliding door interruptions, researchers report Dec. 18 in Science Advances. In contrast, self-cleaning or playing alone has only resumed about 50 percent of the time, on average.
Bonobos usually resumed social preparation with the same partner within a minute of an interruption, usually near the original preparation site. Groomers often occupied the place where they had left in the body of a couple. And bonobos more often vocalized, gestured, or otherwise communicated when restarting social preparation if they had been in charge of initiating the session or interrupting it to get a food reward. This has been especially true for the highest-ranking bonobos in the community, suggesting a certain awareness of breaking a joint commitment and wanting to signal a friendly intention when rejoining lower-ranking grooming partners.
Still, bonobos are likely to think in less complex ways than people about mutual commitments, say Heesen and colleagues. In previous studies, even 3-year-olds were much less willing to interrupt joint tasks for reward than bonobos in new experiments.