Yet another example of how chimpanzees exhibit altruistic behavior toward each other. (Why do we continue to act as though this is surprising or as though we humans are the only moral species?)
Last September, a group of wildlife researchers were studying wildlife in an African rainforest when one of them, Nahoko Tokuyama of Kyoto University in Japan, heard a scream.
It came from a bonobo chimpanzee who had stepped into a snare.
As soon as other members of the group realized that one of their own was trapped, they gathered around him. One of them untangled the snare from vines, enabling him to move. But they still couldn’t free him from the wire. Eventually, at the end of the day, the bonobos returned to the dry forest, more than a mile away, to sleep. The injured male had to be left behind.
Next day, the researchers watched as the bonobo group returned to where their group member had been snared. It turned out he wasn’t there – apparently he’d managed to free himself.
Takeshi Furuichi, another member of the research team, noted that when they see other animals caught in snares, those animals are almost always left behind to die. But not so in this case.
So, what struck the research team was the extent to which the male bonobo’s family and friends had gone in order to help him. Since the area where he’d been trapped was not a particularly good source of fruit, the only reason for them to go back was to help him.
Furuichi suggests that the difference is that bonobo groups are led by females. Most primate groups are led by males, and since males compete, they can benefit by losing other male members. But females need the support of males to help rear their young. That makes for a more caring society.
“It’s the first time we’ve observed this behavior in primates,” Furuichi says in the report. “The unity of the group is more important to them.”
So, what happened to the male who had been snared and, after being helped by his group, had apparently managed to free himself? Six weeks later, the team observed him back with the group.
The following is from the abstract of the report, which you can find here.
This is the first report to demonstrate that a large mixed-sex party of bonobos traveled a long distance to return to the location of a snare apparently to search for a member that had been caught in it.
An adult male was caught in a metallic snare in a swamp forest at Wamba, Luo Scientific Reserve, Democratic Republic of the Congo. After he escaped from the snare by breaking a sapling to which the snare was attached, other members of his party assisted him by unfastening the snare from lianas in which it was caught and licked his wound and tried to remove the snare from his fingers. In the late afternoon, they left him in the place where he was stuck in the liana and travelled to the dry forest where they usually spend the night.
The next morning, they traveled back 1.8 km to revisit the location of the injured male. When they confirmed that he was no longer there, they returned to the dry forest to forage. This was unlike the usual ranging patterns of the party, suggesting that the bonobos traveled with the specific intention of searching for this injured individual who had been left behind.
The incident described in this report likely occurred because bonobos usually range in a large mixed-sex party and try to maintain group cohesion as much as possible.
For another example of cooperation among chimpanzees, go here.