Researchers have released a new study saying that chimpanzees that are raised as pets or performers from an early age face behavioral issues that could last a lifetime.

Even though they are an endangered species and pose a huge threat to health and public safety, it is legal in most states to own a chimpanzee. Around 700 chimps are kept as pets in the U.S.

Researchers from the Lincoln Park Zoo looked at 60 chimps to access the long-term impacts of separation from an early age and determined that it causes behavioral and social deficiencies that last into adulthood, according to a release issued by the zoo.

The team spent 14 months studying animals with a range of personal histories in zoos across North America. Of the chimps studied, 35 were either pets or performers.

"Unusually for a study on this topic, we looked at the degree of human and chimpanzee exposure on individual chimpanzees along a continuum," said Steve Ross, director of the Fisher Centre for the Study and Conservation of Apes at Lincoln Park Zoo.

"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," Ross added.

Chimpanzees with high human exposure spent less time social grooming with other chimps, sometimes for decades after being reintroduced to their own species.

"One of the startling aspects of these findings is that these behavioral effects are so long-lasting," Ross said. "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. As a result, the process of integrating them with other chimpanzees can be challenging, stressful and even dangerous at times."

Ross said that their findings should encourage people to stop keeping chimpanzees as pets due to the detrimental effect it has on the animals.

"Chimpanzees are incredibly intelligent and sensitive animals," said Ross. "Denying them access to members of their own species, during the critical infanthood period, results in behavioral outcomes that last a lifetime. Even with the best possible care as adults, they often can't fit in with the other chimpanzees."

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