Bonobos will share with strangers: study

In a series of experiments, scientists have found that bonobos will share food with strangers.

The study, published in PloS One, was done through a series of tests.

The first test was to get bonobos to choose between sharing with a stranger, a groupmate or just eating the food themselves.

Thus the researchers allowed one bonobo to enter a room with highly desirable food, and open a door either to a group mate or a stranger bonobo they likely hadn't met before. The bonobos overwhelmingly tended to share, and were more likely to share with the stranger than the groupmate.

The second test was supposed to check to see if the bonobos were simply avoiding groupmates, so they set up much as they did before but only one of the doors had another bonobo behind it. This other bonobo was either a stranger or a groupmate.

"Subjects made a clear choice to share monopolisable food with strangers, while they were indifferent regarding groupmates (i.e. they did not avoid or approach groupmates). We thus confirmed that the results in experiment 1 were driven by an inclination to share with strangers," the researchers wrote.

The third test involved the bonobos being trained to pull a rope, that would open a door so that a stranger bonobo could get food that was out of reach. The bonobos in question were kept separate and couldn't interact with each other directly. "To raise the cost of the prosocial act, a novel toy was placed in the subjects' room so that helping also required forfeiting time playing," according to the researchers.

What they found was that in the majority of cases, the bonobos pulled the rope at least once, showing that even in cases with no immediate reward bonobos were inclined to help strangers.

Finally, the researchers upped the stakes and had the bonobos go through the same test again, but this time the food was within the reach of the bonobo who would be allowed to pull the rope. This demonstrated the limit to the bonobos charity as none of them pulled the rope, preferring to eat the food themselves.

"Our results demonstrate that prosociality and even other-regarding preferences toward strangers are not unique to humans," the researchers wrote, "our results also raise the possibility that bonobos have a unique prosocial preference for strangers over groupmates (i.e. while humans share with strangers they do not prefer them over groupmates.)"