Innovative pandanus-tool folding by New Caledonian crows

Abstract

The ratcheting of evolutionary innovations over time has enabled humans to produce complex technology. This process requires (1) technological innovations, (2) the accurate transmission of innovations by social learning, and (3) the faithful maintenance of new technology by its standardised reproduction. Although nonhuman primates are good behavioural innovators, there is no evidence that they have evolved cumulative technology. It has been previously suggested that New Caledonian crows have made cumulative changes to their pandanus tool manufacture. However, technological innovation by individual New Caledonian crows in the wild had not been observed. Here, we report that two distantly related male crows at the same location have a novel way of using pandanus tools by first folding them into a boomerang-like shape. The fine manipulation to fold tools was highly routinised and its two main manipulatory components (direction of head movement and holding technique) were exclusively lateralised. As a consequence the fold arrangement was invariable irrespective of a tool's position before folding. The males' tool-folding confirms that New Caledonian crows have a disposition to routinise and lateralise complex sequences of manipulatory actions. Such a disposition may facilitate the evolution of cumulative technology because it can act to standardise the reproduction of a technological innovation.

Restricted gene flow and fine-scale population structuring in tool using New Caledonian crows

“…However, it is currently impossible to assess the significance of such effects as the species' dispersal and recruitment strategies are unknown. To advance with these questions, we conducted a first detailed genetic study, examining population structuring, gene flow and local relatedness patterns in a suite of study sites (the relatedness of a few selected birds had previously been examined on the sister island Maré; Hunt et al 2007). Using microsatellite and mt-haplotype profiling, we show that New Caledonian crow populations can exhibit a substantial degree of fine-scale structuring.…”

A complex adaptive system may be essential for cumulative modifications in tool design

“…This disposition, though, does not exclude learning and innovation in the development and transmission of their tool behaviour (Hunt & Gray, 2007;Hunt et al, 2007b). Indeed, technological improvement in tool design is likely to be underpinned by adaptations supporting both fixed phenotypes and flexible mechanisms (Meulman et al, 2012).…”

“…Their innovative foraging techniques in the wild (e.g. Hunt et al, , 2007bHunt, 2014) and impressive problem solving ability under experimental conditions (e.g. Taylor et al, 2010Taylor et al, , 2012 demonstrate that they can develop innovative foraging solutions, despite having a genetic disposition specifically for basic tool use.…”

Is primate tool use special? Chimpanzee and New Caledonian crow compared

“…In finalizing the making of a hook tool, the crows 'sculpt' the hook from the existing fork of a twig, by bending the end of the twig, removing small pieces of wood, and sharpening the point [16,20,46]. They fold the wide tools made of Pandanus leaf [22].…”

“…Most notable is the sculpting of hook tools from particularly detached twigs [14,16,46], a form of non-human extractive technology shown only by NCC. Whether detaching bits of a flat object such as a Pandanus leaf is three-or only twodimensional is unclear, but folding the leaf to create a new shape surely qualifies [22]. Wire-bending by captive crows to make hooked tools, albeit with artificial raw materials, shows comparable extractive function [47, but cf.…”