Tool use task as environmental enrichment for captive chimpanzees

Wild chimpanzees spend 50-80% of their time foraging, using tools and other forms of manipulation, while captive chimpanzees cannot. In this study, a device-honey in a bottle to be "fished" with artificial materials-that elicits tool use was presented to six captive chimpanzees housed in pairs. The task successfully reduced inactivity by about 52%, increased foraging opportunity from 0 to around 31% and elicited tool use and manipulation. Dominants, who had more access to the device, showed significantly more behavioural changes than subordinates. There was no statistical evidence of habituation to the device, though there was evidence of habituation to the materials. The task effectively extended the subjects' behavioural repertoire in the direction of that of wild chimpanzees. (C) 2002 Elsevier Science B.V. All rights reserved.