Acquisition and transmission of tool making and use for drinking juice in a group if captive chimpanzees (Pan troglodytes).
Rikako Tonooka, Masaki Tomonaga, Tetsuro Matsuzawa
The present study examined the acquisition and transmission of tool making and use in a group of chimpanzees. We set up a piece of apparatus that provided orange juice in an outdoor compound for a group of nine chimpanzees. Although they could reach the juice with their hands, eight of the nine subjects used tools. Fifteen kinds of tools in total were used, such as straw, twigs, and some kinds of leaves. The chimpanzees showed high selectivity with regard to tool type. They preferred to use Thuja occidentalis as a tool although there were 28 species of tree and several kinds of grass available in the compound. Two females initiated the use of the Thuja tool. Since then, five other individuals have begun to use it selectively. Before making the tools by themselves, these five chimpanzees first watched others using the Thuja tool for drinking juice, and then used the Thuja tool which had been used and left by another chimpanzee.
chimpanzees, tool use, acquisition, transmission