DNA helps solve riddle of how clever crows craft tools

Image: James St Clair - A clever piece of detective work by an international team, including a researcher from The Australian National University (ANU), has helped solved the mystery of which plants a population of crows on New Caledonia use to craft tools. The crafty crows are well known for making their own stick tools with hooked tips to retrieve invertebrate prey from small holes and crevices. The New Caledonian crow is the only non-human animal known to manufacture hooked tools in the wild.  "They put a lot of effort into making them. They use specific plants with forked stems, which they remove and then process into hooked tools for foraging," study co-author Dr Linda Neaves from ANU said.  "But they remove leaves and much of the bark, making it impossible to quickly identify the plant species."   While Dr Neaves' collaborators from the University of St Andrews in Scotland had been able to determine what plants the crows were using to make these tools at two of their long-term study sites, a third remained a puzzle.  "The plants used in one of the study sites is an introduced shrub, and in the other, they seem to use a variety of raw materials. But no one had ever seen the crows make the tools at the third site, so we had no idea what species it was," Matthew Steele from the University of St Andrews said. After years of trying to work it out using a range of approaches - including behavioural observations in the wild and in field aviaries, radio-tracking of birds, and working with local botanists to examine collected tools - the crow team was at a loss.