Chimpanzees who spend their formative years away from mom - which is what happens when they are raised as pets or entertainers - act abnormally even decades after separation.
Until about age seven, wild chimpanzees are inseparable from their mothers. These first few years are a critical time for young chimps to learn from older relatives and gain insight into everything from tool use to grooming skills.
But chimpanzees raised among humans, rather than other chimps, spend less time grooming each other, according to a recent study in the journal PeerJ. And the importance of chimp grooming cannot be understated. It's "the glue of their society," says animal behavior expert Steven Ross, an author of the study, to the Dodo.
Ross, a chimpanzee conservationist at Lincoln Park Zoo in Chicago, is the director of a program called Project ChimpCARE, which began in 2008. It's a response to "more and more calls from private owners" who were looking to place chimpanzees in zoos, he says.
Although chimpanzees are an endangered species, it's legal to privately own the animal in several states. There are roughly 200 chimps in private hands in the United States - that is, apes raised as pets, for entertainment, or living in small roadside zoos. To see how these animals fared after being returned to a more natural social structure in a zoo or sanctuary, Ross and his colleague Hani Freeman made detailed observations of 60 chimpanzees across the U.S.