Spontaneous Invention of Ladders in a Group of Young Chimpanzees

Abstract

One member of a social unit of 8 wild-born captive chimpanzees learned to gain access to elevated points such as windows and trees by using a pole as a bridge between two points. ‘Ladder making’ behavior soon spread across the rest of the group. In some cases 2 or more animals collaborated in setting up poles. This paper describes the developmental history and the social background of this behavior, and indicates its implications for theories of nonhuman tool-using.