Chimpanzees who spend time with humans when they are young have issues adjusting to live with their peers later in life.
Those who were removed from their mothers early in life and raised by humans as pets or performers are likely to show behavioural deficiencies as adults, scientists say.
In a year-long study, researchers from Lincoln Park Zoo in Chicago observed 60 chimpanzees and concluded that those who were removed from their mothers early in life and raised by humans as pets or performers are likely to show behavioural and social deficiencies as adults.
Over the course of 14 months the researchers studied 60 chimpanzees with a range of personal histories, all of whom were living in a variety of zoos.
Of their study group, over 35 of the chimpanzees were former pets or performers.
The results suggest that chimpanzees raised primarily around humans with less experience around their own species during the first four years of life, tend to show reduced social competencies as adults than those with more natural early histories.
Specifically, chimpanzees with high human exposure in life tended to engage in less social grooming with their group-mates, a critically important behaviour for social bonding in chimpanzees.
Strikingly, these effects were expressed years, sometimes decades after their lives as pets and performers were over.
The study “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,” said Steve Ross, director of the Fisher Centre for the Study and Conservation of Apes at Lincoln Park Zoo.