Behaviour 2019
Bending and unbending of tools by New Caledonian crows (Corvus moneduloides) in a problem-solving context. †
Magdalena van Buuren1, Jessica Alfredsson2, Berenika Mioduszewska1, Sabine Tebbich1, Auguste von Bayern3. 1University of Vienna, Vienna, , Austria; 2UmeŚ University, UmeŚ, , Sweden; 3Max Planck Institute for Ornithology, Seewiesen, , Germany

New Caledonian crows (NCCs) are proficient tool makers. Tool bending by a captive NCC in 2002 has been cited as a striking case of causal reasoning in an animal. Further studies examining the flexibility of this behavior in a problem-solving context are lacking. Here we tested a total of 17 captive NCCs in one tool bending and three unbending tasks. In the first bending and unbending tasks, the subjects were trained in the use of the correct tool before being tested with pliant but inadequate tools. Three out of five subjects bent tools and one out of five unbent tools consistently. In the second unbending task, subjects were untrained and were provided with a tool requiring two straightening actions to reduce the possibility of accidental modification. Four out of ten subjects solved the task at least once, and two did so consistently. In the third unbending task, the subjects were challenged in a task requiring a novel unbending behavior. One NCC succeeded in both unbending tasks. From our results, NCCs could flexibly bend or unbend pliant materials to solve a novel task. The underlying mechanisms varied across individuals, although trial and error learning prevailed.