Chimpanzees need parental guidance to play safely
In central Zambia, at the Chimpanzee Wildlife Orphanage, dozens of parentless chimpanzees grow up in companionship, without adults. This is a successful arrangement for the young chimpanzees, because in the wild, orphanhood can lead to death.
But even in the shelter, life without parents has its drawbacks. Studies conducted on a wide variety of social animals have shown that normal social development depends on the presence of mature individuals, so orphans are at a disadvantage.
To find out how maternal nurturing shapes the interactions between chimpanzees, researchers monitored the play of two populations of young chimpanzees: a group of orphans and a group of chimpanzees whose parents had raised them. Surprisingly, the orphans initiated the game more often than the members of the mother-supervised group. "I was relieved to see that the orphans were highly motivated to try and play because it is commonly seen as a sign of mental health," says research student Edwin van Leeuwen, who led the study at the Max Planck Institute for Psycholinguistics in Nijmegen, the Netherlands.
But even though the orphaned chimpanzees loved to play, they didn't always excel at it. For the most part, the games lasted less than 60 seconds, compared to the non-orphan chimps' games which lasted several minutes at a time. Also, the study published in the Journal of Animal Cognition reports that the orphans' play turned violent five times more often than the play of their non-orphan peers.
What prevents the play of chimpanzees raised under maternal supervision from degenerating into violence? They may have learned to use subtle cues that allow for a calm atmosphere. It is easy to mistake and interpret many play behaviors, such as biting and hitting, as aggression, and growing up around adults may teach the young the rules of friendly behavior.
And it is possible that the strict supervision of the mother from a young age sets sustainable limits. If mothers consistently intervene when the game gets out of hand, "then over time, the young raised that way learn not to escalate," says Claudio Teni, a monkey researcher at the University of Birmingham in England.
The good news is that the young orphans have plenty of time to learn social norms. "Orphans can mature into a fairly competent social life," says van Leeuwen, "as long as they have the opportunity to live a life of freedom in a large and appropriate environment with many other monkeys." According to him, in Chimpanzee there are four such groups that include adult orphans and that overall "they look healthy and stable and have typical behavior of chimpanzees."
