LAST September, deep in the swamp forest of the Democratic Republic of the Congo, Nahoko Tokuyama of Kyoto University in Japan heard a scream. It came from a male bonobo whose hand was trapped in a snare. What happened next shows that bonobos (Pan paniscus) don’t forget their lost friends, and will travel long distances to find them. This caring behaviour may be down to the species’ female leadership.
The snares are set to catch other species, says Tokuyama’s colleague Takeshi Furuichi. Injured animals almost always get left behind and die.
Not so for bonobos. As soon as the other group members realised the male was trapped, they gathered around him. One untangled the snare from woody ground vines, enabling the male to move. Another tried and failed to remove the wire. Later in the day, the bonobos returned to the dry forest to sleep. The injured male could not follow.
The next morning, to the researchers’ surprise, the bonobos travelled almost 2 kilometres back to where they had last seen their injured friend. The animals had already ruled out the area as a good source of fruit, suggesting they went back just to find him. He had moved on, but rejoined the group six weeks later (Primates, DOI: 10.1007/s10329-012-0298-2). “It’s the first time we’ve observed this behaviour in primates,” says Furuichi.
Amy Cobden at Emory University in Atlanta, Georgia, says she has “never seen this behaviour before”, but it is not surprising given bonobos’ nature. “They seem very concerned for each other’s emotional status.”
Furuichi thinks bonobo society is so caring because groups are led by females, who need support to rear their infants. “The unity of the group is more important to them,” he says. Most primate groups are led by males, who can benefit by losing other male members.