DNA barcoding identifies cryptic animal tool materials

Some animals fashion tools and other constructions out of plant materials to aid foraging, reproduction, self-maintenance, and protection. The choice of raw materials can affect the structure and mechanical properties of the resulting artefacts, with significant fitness consequences. Documenting animals’ material preferences is challenging, however, as manufacture behaviour is often difficult to observe directly, and materials may be processed so heavily that they lack identifying features. Here, we use DNA barcoding techniques to identify, from just a few recovered tool specimens, the plant species New Caledonian crows (Corvus moneduloides) use for crafting elaborate hooked stick tools in one of our long-term study populations. The method succeeded where extensive fieldwork using conventional approaches had failed, including targeted observations, radio-tracking, bird-mounted video-cameras, and behavioural experiments with wild and temporarily captive subjects. We believe that DNA barc...