Chimpanzees should not be raised as pets. When young chimpanzees are taken away from their mothers in the first four years of their lives, they wind up with poor behavioral and social tendencies later in life.

This is the first long-term study done on the effects of raising chimpanzees away from other chimpanzees. The study was published Sept. 23 in the journal PeerJ. The study was led by Steve Ross, Ph.D., who directs the Fisher Center for the Study and Conservation of Apes at Lincoln Park Zoo.

The study followed a group of 60 chimpanzees over the course of 14 months. The chimpanzees all lived currently in zoos or sanctuaries associated with either the Association of Zoos and Aquariums or the North American Primate Sanctuary Alliance.

A little more than half of the chimpanzees studied (over 35 of the 60) were pets or performers before they entered the zoo or sanctuary. The study found that the chimpanzees who had more experience with humans than with other chimpanzees in the first four years of their lives had fewer social abilities than chimpanzees who had been raised with other chimpanzees from birth. One of the biggest differences was that the chimpanzees who had been raised by humans showed less interest in social grooming, which is an important part of chimpanzee social life. The researchers found that this was true even years after the chimpanzees had left the humans and gone to live with other chimpanzees.

"Unusually for a study on this topic, we looked at the degree of human and chimpanzee exposure on individual chimpanzees along a continuum," said Ross. "This showed that those chimpanzees with more atypical beginnings to their lives, spending much more time with humans than with their own species, tended to behave differently than those that stayed with their family through infanthood."

Chimpanzees are the primate most closely related to humans. This study sheds new light on the importance of bonding with mothers early in life for chimpanzees.

Chimpanzees are currently endangered. However, it is legal to own a chimpanzee as a pet or for use in performances. Many chimpanzees wind up in zoos or sanctuaries after being kept by humans when their owners decide they are too much work to care for. This study shows that keeping a chimpanzee for personal or public use away from a social group of other chimpanzees has real, lasting damage to the chimpanzee's social well-being. Ross said that he hopes this study will help discourage the use of chimpanzees as pets or performers in the United States.