A new study found that chimpanzees raised as performers or pets have higher chances of developing social problems that will lead into their adulthood, according to The Washington Post. 

Study leader Dr. Steve Ross of the Fisher Center for the Study and Conservation of Apes at the Lincoln Park Zoo (Illinois) and his colleagues observed 60 chimpanzees from various zoos and sanctuaries for 14 months. Thirty-five chimpanzees were once performers or were raised as pets.

Researchers' observations revealed that chimpanzees raised primarily around humans with less experience around their own species during the first four years of life, showed reduced social competencies as adults compared to those with more natural early histories. Chimpanzees that were accustomed to life with humans did not engage in social grooming with their groupmates.

Social grooming is a common practice among chimpanzees in which they help others to maintain their appearances. It is also a means of bonding, building relationships and resolving conflicts. Social grooming also involves gentle touches, stroking, scratching and massaging.

"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 infant hood," Dr. Ross explained in a press release.

The study highlighted the importance of maternal care on the behavioral development of primates.

Chimpanzees that were previously performers or pets are often turned over to sanctuaries and zoos once they become old enough, or if the previous owner cannot take care of them anymore.

Chimpanzees are listed as endangered species, but in the United States, the law permits a person to keep one as a pet. Ross expects that the findings of their study will help shift the policy towards providing better care for the chimpanzees.

Further details of the study were published in the Sept. 23 issue of the journal PeerJ.