Tool using behaviour in animals

Initially, scientists considered that human beings were the only organisms able to use and manufacture tools. Early studies developed by Köhler (1925), Yerkes & Yerkes (1929) and Goodall (1970) shed light on this topic. At present, there is striking evidence supporting that this type of behaviour is widespread across many species. Although there is a general consensus on the importance and the evolutionary implications of animal tool use, there is no complete agreement on its definition instead. Beck (1980) elaborated the most influential proposal to describe this behaviour and his first version has recently been revisited and updated (Shumaker et al, 2011). This new version defines tool use as: “The external employment of an unattached or manipulable attached environmental object to alter more efficiently the form, position, or condition of another object, another organism, or the user itself, when the user holds and directly manipulates the tool during or prior to use and is responsible for the proper and effective orientation of the tool”. From this perspective, these authors consider that when an agent only manipulates the object to be altered instead of manipulating the tool, it is proto-tool use and not true tool use. The term “tool” refers to an object or organism which is manipulated by the agent, and by definition it has to be external to the user itself, i.e. it must not be an attached part of the agent´s body. There is a vast variety of reports on different objects used as tools, e.g. sticks, wands, stones, leaves, mud, and other objects supplied within experimental contexts. Characterization of an object/organism as a tool implies the identification of a motor pattern, performed by the agent, which involves the use of this entity to produce a modification in another object. If the tool is modified prior to use, this modification is considered tool manufacture. Beck recognizes four modes of tool making: detach, subtract, reshape and combine. Tool using behaviour by non human primates provides foundations to generate hypotheses about the origins of human technology. Ethological studies on non-human primates in nature have revealed local behavior repertoires that are highly distinctive of different communities. Much of this cultural variation is related to problem solving mediated by the use of tools (McGrew, 1992; Whiten et al, 1999; Avital & Jablonka, 2000; Whiten & Boesch, 2001), and the acquisition of these population-specific techniques is based on socially biased learning. In the last decades tool use in animals has received much attention and a huge number of observational and experimental studies have been conducted, especially with Aves and Mammalia orders.