Some people want to raise chimpanzees as pets because they are brilliant and clever animals, but a new study reveals why raising pet chimps isn't really a good idea.

When chimpanzees are raised as pets, it appears they lose their ability to interact well with other chimps. They are also characterized by behaviors that are different compared with their counterparts and these can persist for years, even decades, after they have been transferred to a healthy sanctuary.

For the new study, "The impact of atypical early histories on pet or performer chimpanzees", published in the PeerJ on Sept. 23, Steve Ross and Hani Freeman from Lincoln Park Zoo's Lester E. Fisher Center for the Study and Conservation of Apes, conducted a study of 60 chimpanzees, which were all living in either sanctuaries or zoos. Of these chimps, 35 were former performers or pets.

The researchers found that the animals that were raised by humans and had less experience interacting with their own species during their first four years of life were more likely to exhibit reduced social competencies when they reach adulthood compared with their counterparts who had natural histories with other chimpanzees during their early years.

The chimpanzees that had more exposure to humans, in particular, were observed to engage less in social grooming behaviors, which scientists believe is an expression of friendship and social bonding among these animals. Ross explained that the failure to reciprocate grooming among chimps is equivalent to ignoring a handshake among humans.

"Grooming is the glue that holds chimpanzee society together," Ross said. "We found chimpanzees that were around humans a lot early in life tended not to do a lot of this behavior, even much later, after they learned to live with other chimpanzees. They just weren't good at maintaining these social bonds, and that was expressed by these lower rates of grooming."

Ross and Freeman also observed that the chimps that were raised by humans had lower frequencies of social and sexual behavior as adults compared with chimps that were more exposed to their own kind.

"One of the startling aspects of these findings is that these behavioral effects are so long-lasting," said Ross. "Chimpanzees which have found new homes in accredited zoos and good sanctuaries continue to demonstrate behavioral patterns that differentiate themselves from more appropriately reared individuals."