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Captive Chimpanzees Show Signs Of Mental Illness

06/27/2011 11:48 am ET | Updated Aug 27, 2011

Repetitive rocking and self mutilation are not animal behaviors you'd expect to see on your visit to the zoo, but according to new research compiled by the University of Kent's School of Anthropology and Conservation, and published in the online journal PloS One, that might be something seen more in zoos around the world.

Research conducted by Dr Nicholas Newton-Fisher and Lucy Birkett show "serious behavioral abnormalities" among captive chimpanzees. The study was conducted among 40 socially-housed chimpanzees from zoos around the U.S. and UK and determined that the abnormal behavior, which is similar to symptoms of mental illness in humans, was prevalent despite efforts by zoo keepers to create a social atmosphere.

As an article by ScienceDaily reported, the "abnormal behaviors" have been attributed to the fact that many of the zoo-bound chimpanzees live in environments dissimilar to their natural habitat, and have controlled diets instead of hunting and gathering in the wild.

Newton-Fisher told ScienceDaily he doesn't believe the emergence of abnormal behaviors is from lack of care from zoologists.

"The best zoo environments, which include all zoos in this study, try hard to enrich the lives of the chimpanzees in their care," he said. "Their efforts include providing unpredictable feeding schedules and extractive foraging opportunities, and opportunities for normal social interactions by housing chimpanzees in social groups. There are limits to what zoos can provide, however; the apes are still in captivity."

Despite the many efforts to make zoo environments more like home, Newton-Fisher thinks more dramatic action might need to be taken.

"We suggest that captivity itself may be fundamental as a causal factor in the presence of persistent, low-level, abnormal behavior -- and potentially more extreme levels in some individuals. Therefore, it is critical for us to learn more about how the chimpanzee mind copes with captivity, an issue with both scientific and welfare implications that will impact potential discussions concerning whether chimpanzees and similar species should be kept in captivity at all."

These results come on the heel of another study published in PloS ONE, which found that some apes are capable of "insightful reasoning" when faced with a complex problem.

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