Compound tool construction by New Caledonian crows

A M P Von Bayern,A Kacelnik,S Danel,B Mioduszewska,A M I Auersperg

doi:10.1038/s41598-018-33458-z

Abstract

The construction of novel compound tools through assemblage of otherwise non-functional elements involves anticipation of the affordances of the tools to be built. Except for few observations in captive great apes, compound tool construction is unknown outside humans, and tool innovation appears late in human ontogeny. We report that habitually tool-using New Caledonian crows (Corvus moneduloides) can combine objects to construct novel compound tools. We presented 8 naïve crows with combinable elements too short to retrieve food targets. Four crows spontaneously combined elements to make functional tools, and did so conditionally on the position of food. One of them made 3- and 4-piece tools when required. In humans, individual innovation in compound tool construction is often claimed to be evolutionarily and mechanistically related to planning, complex task coordination, executive control, and even language. Our results are not accountable by direct reinforcement learning but corroborate that these crows possess highly flexible abilities that allow them to solve novel problems rapidly. The underlying cognitive processes however remain opaque for now. They probably include the species’ typical propensity to use tools, their ability to judge affordances that make some objects usable as tools, and an ability to innovate perhaps through virtual, cognitive simulations.

Highlights

Tool-related behavior, especially innovative tool manufacture, is intimately associated with human evolution, and may have co-evolved with specific neurological capacities, planning and complex task coordination[1]
We focus on a rare form of tool innovation, a type of tool manufacture that anthropologists and primatologists consider profoundly significant for understanding human evolution[1]
Innovative compound tool construction has been documented only through a few reports in captive great apes[7,8,10,13,14] and some authors consider it to be absent in wild chimpanzees (Pan troglodytes)[15,16]

Summary

Introduction

Tool-related behavior, especially innovative tool manufacture, is intimately associated with human evolution, and may have co-evolved with specific neurological capacities, planning and complex task coordination[1]. The components have specific roles (anvil, wedge, hammer) and are chosen and placed appropriately to make the assemblage functional, but this assemblage forms a tool and substrate composite rather than a compound tool, which is an integrated mobile object[14] In another example, at the Sonso community in Budongo Forest, Uganda, wild chimpanzees hold together multiple leaves and use them as sponges to extract water or honey from cavities[15]. The bundles of leaves are jointly mobile, but they form loose, amorphous aggregates of equivalent parts, and it is debatable whether, for the purpose of understanding tool-related cognition, it is useful to integrate them in the category of compound tools How such tool technologies are discovered and adopted by individual members of different natural populations is an important but as yet largely unsolved problem. It would provide a novel and independently evolved biological model[30] to help understanding the associated cognition

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