Chimps raised among humans may have problems as adults

There are plenty of good reasons why chimpanzees should not be pets or performers, no matter how cute or humanlike they appear: They are wild animals. They can be violent with each other. And they can be violent toward humans — even humans that have a long history with the chimp. Plus, there’s evidence that seeing an adorable chimp dressed up like a miniature human actually makes us care less about the plight of their species.

Now comes evidence that the way that chimps are raised to become pets or entertainers — taking them away from other chimps at a young age and putting them in the care of humans, who may or may not feed and care for them properly — has long-term, negative effects on their behavior. “We now add empirical evidence of the potentially negative welfare effects on the chimpanzees themselves as important considerations in the discussion of privately owned chimpanzees,” Hani Freeman and Stephen Ross of the Lincoln Park Zoo in Chicago write September 23 in PeerJ.

Freeman and Ross compiled life history and behavioral data on 60 captive chimps living in zoos. Some of the animals had always lived in zoos and grew up in groups of chimpanzees. Six were raised solely by humans and were later placed in zoos after they became too big or too old for their owners to care for them. Others had a more mixed background.

The researchers looked at the relationship between the various aspects of the chimps’ behavior and the degree of contact chimps got before the age of four with both humans and chimps. The less contact the animals had with other chimps, the more likely they were to not groom other chimps in their group, and the less likely they were to exhibit sexual behavior such as mounting. “Grooming and sexual behavior are important components to the dynamics of social groups in chimpanzees,” the researchers note. “Decreases in these behaviors could have the potential to be related to animal management and welfare issues connected with social interactions between chimpanzees.”

In other words, keepers shouldn’t expect the chimps raised with humans to interact in the same ways as chimpanzees that were raised with others of their species. And those differences in interactions could affect a chimp’s well-being.

Not every chimp had similar problems, though, Freeman and Ross note. Some of the human-raised chimps fit in with the other chimps better than others. The researchers don’t know why, but it might have something to do with how they are managed in the zoos, which could be something to investigate in the future.