Pruetz, J. D. E., McGrew, W. C. 2001. What does a chimpanzee need? Using natural behavior to guide the care and management of captive populations. In: Special Topics in Primatology, volume 2. The Care and Management of Captive Chimpanzees.
Their tendency toward natural behavior is probably little changed from their wild counterparts, despite the overwhelming influence of captivity on behavior... From a chimpanzee's point of view, it would be better to stimulate behavior characteristics...