New Caledonian crows show behavioural flexibility when manufacturing their tools

摘要

New Caledonian crows have demonstrated flexible behaviour when using tools and solving novel problems. However, we do not know whether this flexibility extends to tool manufacture. Here, we show that these crows respond to different tool-using problems by altering the length of the tools that they manufacture; on average, crows made shorter tools for tasks requiring short tools and longer tools for tasks requiring long tools. They continued to do so when they could not simultaneously see the tool-manufacturing material and the apparatus requiring the use of a tool. Despite altering the length of their tools, the crows frequently did not make tools short or long enough to reliably extract the bait, though this may have been due to shortcomings in the task presented to them. Our results demonstrate that these crows have a degree of behavioural flexibility when making tools, which may be used in the wild during foraging.