Manufacture and use of hook-tools by New Caledonian crows

TOOL behaviour in wild birds has been described as mostly stereotyped(1,2), and tool manufacture involves little modification of material(3-5). Here I report in New Caledonian crows Corvus moneduloides the manufacture and use of two different types of hook tool to aid prey capture: hooked-twig and stepped-cut barbed pandanus leaf. Crow tool manufacture had three features new to tool use in free-living nonhumans: a high degree of standardization, distinctly discrete tool types,vith definite imposition of form in tool shaping, and the use of hooks. These features only first appeared in the stone(6) and bone(7) tool-using cultures of early humans after the Lower Palaeolithic(6,7), which indicates that crows have achieved a considerable technical capability in their tool manufacture and use.