When and how do non-human animals develop tool use? Is tool use a latent ability in many species that arises when necessary, or does it require a necessary degree of cognitive evolution?
A recent study demonstrates that at least in one species, tool use arose facultatively in response to a new-- but tough to crack!-- prey species, suggesting that the cognitive groundwork is already present. The great antshrike, a red-eyed species of bird native to Brazil, has been observed using stone anvil tools to break open the shells of an invasive species of land snail. Before the land snail was introduced in the 1980s, the great antshrike had never been observed using tools.
The authors of this study suggest that three factors facilitated the learned tool use in great antshrikes:
1) There was a problem that would be difficult to solve without a tool: the tasty and nutritious land snails are encased in a large, hard shell.
2) Because the great antshrike is an omnivore, it "already had a broad repertoire of prey-capture behaviors and was thus a good candidate for tool-using behavior."
3) the practical difficulty of the required tool-- a stone anvil-- was quite low.
Thus, the flexible and innovative antshrikes could adopt this straightforward method of shell-crackin'. But what steps are required to transition from facultative and relatively basic tool use to the highly developed and specific tool manufacture evident in New Caledonian Crows? The same questions might apply to our own human ancestors.
In the meantime-- caviar, anyone?
Many thanks to the marvelous Paul Manning, Oxford DPhil Candidate in Zoology, for sending along yet another excellent article!
There are few examples of facultative tool use in animals under natural conditions. We provide the first description of tool use in great antshrikes (Taraba major), which were observed using stone anvils to break the shells of the land snail (Achatina fulica). This behavior is almost certainly of extremely recent origin given the lack of previous reports of tool use in T. major and the very recent (1980s) introduction of A. fulica into Brazil. Tool use in this particular population is probably a flexible behavioral trait that arose in response to the high density of exotic snails in this locality.