Bird and Emery make the fascinating observation that rooks, who do not use tools in the wild, are capable of insightful problem solving related to sophisticated tool use, including spontaneously modifying and using a variety of tools, shaping hooks out of wire, and using a series of tools in a sequence to gain a reward. They suggest that the ability to represent tools may be a domain-general cognitive capacity rather than an adaptive specialization and question the relationship between physical intelligence and wild tool use. That is, they question the common invoking of tool use as a candidate trait (together with language, cumulative culture, and excessive prosociality) for promoting the development of human intellectual uniqueness. (I might point to the ongoing debate on whether animals other than humans have causal beliefs, see Wolpert and Shettleworth's letters to nature which comment on an essay by Bolhuis and Wynne, mentioned in a previous MindBlog post.
Bending wire into hooks by rooks. (Left) Fry extracting the bucket containing a worm using a piece of wire she had just bent. This photo was taken after the experiment was completed but the hook and posture are typical of experimental trials. (Right) Photographs of the successful hooks used by all 4 subjects (excluding the 2 trials where the straight wire was used to stab the bucket), with the successfully used end facing right. Numbers indicate trial number.