A note on enrichment for spontaneous tool use by chimpanzees ( Pan troglodytes)

Abstract

In the wild, decisions as to “when”, “where”, and “how” an animal acts are made based on the individual’s own choice; in contrast, the behaviour of wild animals in captivity may be under human control. To improve the physical and psychological well-being of captive animals, we should ensure that animals act on their own will, by ascertaining the voluntary nature of their behaviour. So far, most feeding enrichments permit an animal to use only one type of processing for each food item. This study was designed to permit voluntary tool-using behaviour by chimpanzees. Tube feeders from which chimpanzees could access orange juice using either tools or their hands were presented. Results showed that chimpanzees opted to use tools to access the juice in the feeders, even though the use of the mouth and the hands to obtain juice continued to occur intermittently until the end of the task. This finding demonstrated that when chimpanzees have the option to access juice through a variety of methods, they employ all available choices. It also supported the hypothesis that the behaviour of captive chimpanzees may come to resemble that of their wild counterparts as a function of behavioural freedom.