Crows are so smart that they seem to understand the concept of tool value

A new study has shown that crows can assign value to their tools, just as we do.

“Many of us will bother with a brand new phone and make sure it is not scratched, lost or lost. But we can handle an old phone with a cracked screen quite carelessly,” said behavioral ecologist Barbara Klump now at the Max Planck Institute, Germany.

New Caledonian Collars (Corvus moneduloides) are so well known for their ingenuity that scientists have used them as a model to help puzzle over the development of tool use and associated behaviors such as planning.

Not only can these clever crows use found objects as tools, they can shape or even build them from several parts that are individually useless – something previously only observed before in primates.

In the wild, they use these twig tools, carefully held in their beaks, to bother larvae that are safely tucked away in wood slits. The larvae will bite the tool defensively so the birds can retreat and eat it. But crows have to put their tools away while eating so they can fall to the ground or even be stolen.

The researchers used 27 wild-caught crows for their experimental experiments so that their results were not biased by previous training.

By offering the crows a choice between the two tool types, the team confirmed that the birds strongly preferred to use hooked stick tools.

Non- (left) and hooked (right) tools and their use. (James St Clair et al, Nat. Ecol. Evol, 2018)

“Hooked tools are not only more expensive to obtain, but they are also much more efficient,” explained University of St Andrews behavioral ecologist Christian Rutz.

“Depending on the foraging task, crows can extract prey with these gears up to 10 times faster than with bog-standard non-hook gears.”

Seventeen of the birds were then observed during two experiments each on separate days. In both, they were presented with tree trunks that contained holes of various sizes with bait with meat or spiders. In one treatment, they had access to branches suitable for hooked tool constructions, and the other with only straight sticks.

Subjects were significantly more likely to express storage behavior (storage of tools underfoot or in holes) when foraging with hooked stick tools they had manufactured … than when foraging with stick tools without hooks they had retrieved from blade debris , “the team wrote in their paper.

This remained true as the connected tools were provided by researchers, suggesting that the tool itself was subject to assigned value rather than the time they put into it.

In addition, they used the safest storage method – storing tools in holes – far more for hooked tools.

“It was exciting to see that crows are just a little more careful with tools that are more efficient and more expensive to replace,” said the University of St. Louis. Andrews ethologist James St Clair.

“This suggests that they have some perception of the relative ‘value’ of different tool types.”

Given corvettes, including ravens and New Caledonian crows, have also shown the ability to plan ahead, and it makes sense that they can also assign value to the objects they use to help prioritize them.

The team notes that not all New Caledonian crows make the hooked stick tools, so their results can only be generalized across the populations that do. Their sample size was also too low to fully address some of the variables, such as material selection, they admit.

But at least one other collar species, the Hawaiian collar (Corvus hawaiiensis) has also demonstrated such storage behavior.

We have long underestimated the abilities of birds given their relatively small brains. But physiological studies have shown that the dense packing of their neurons outweighs what they lack in size.

Behavioral studies constantly reveal that these modern dinosaurs are capable of behaviors that we once only thought humans were capable of – such as self-control – evidence, like everything else biological, intelligence is a complicated and messy spectrum that is not just spontaneous occurred with the arrival of our species.

This study was published in eLife.

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