Direct observations of pandanus-tool manufacture and use by a New Caledonian crow (Corvus moneduloides)
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New Caledonian crows are reported to have impressive pandanus-tool manufacture abilities. These claims are based on an extensive artefact record. However, inferring behavioural and cognitive abilities without direct observation of tool manufacture is problematic. Here we report (and document on video) direct observations of a crow making and using stepped pandanus tools at Pic Ningua. We observed (1) a bias for making tools on left edges consistent with that previously found at the site, (2) faithful manufacture of a stepped design with high overall congruence in the shapes of tools, (3) the use of convergent rips to first form the tapered end working away from the trunk then the wide end working towards the trunk, (4) appropriate functional use of stepped tools by use of the leaf-edge barbs to hook food from holes, and (5) consistent holding of tools on the left side of its head when using them. Our observations verify most of the claims based on the artefact record, but the crow’s exact manufacture technique was slightly different to that inferred previously.
KeywordsNew Caledonian crow Pandanus-tool manufacture and use Laterality
The accompanying video clip shows the crow manufacturing a two-stepped pandanus tool on the left edge of tree B (anticlockwise-spiralling leaves). The tool, which is shown in Fig. 1, is 17.7 cm long. The bird first forms the tapered section, working away from the trunk. The process ends with a rip (rip A in Fig. 4). It then moves its bill to a position past the end of rip A and proceeds to cut in from the leaf edge. The distance of the cut in from the edge generally matches the distance of rip A in from the edge. After completing the cuts at the wide end, the crow rips the end back towards the trunk (rip B) to meet rip A. The tool is then removed from the leaf and the manufacture is completed. Note that the crow inverts its head to manufacture the tool.
Hunt_Gray_animation.mpeg (1.94 MB)