Stone the crows – New Zealand scientists have discovered the cunning birds seem to understand basic physics.
In one of Aesop's fables illustrating the virtue of ingenuity, a crow was able to drink from a half-filled pitcher by dropping stones in it to raise the water level.
In a re-creation of the fable, Auckland University psychology researchers Dr Gavin Hunt, Professor Russell Gray and Dr Alex Taylor presented wild New Caledonian crows with a tall half-filled tube of water, which had a small piece of meat floating on the surface.
When given a collection of stones, each of the four birds – Pepe, Caesar, Mimic and Laura – quickly learned to drop them into the tube to raise the water level, allowing them to fish out the food.
They were even more clever than that, however. When given a selection of small and large stones, the crows picked out the large stones, which displaced more water at once and brought the food within reach more quickly.
"[The] crows showed an immediate preference for large, rather than small stones, with two crows actually discarding small stones the first time they picked them up and before they had observed their effect on the water level," the researchers wrote.
The crows were also tested with heavy and light objects, with all of them choosing rubber cubes over polystyrene cubes the same shape and size.
The results of the various experiments showed the birds actually understood what they were doing, rather than simply doing something because it worked the first time, the researchers wrote.
"The differences between the causal and arbitrary tasks that we presented to the crows strongly suggest that cognitive mechanisms other than simple associative learning are involved."
The study has been published in PLoS ONE, widely seen as one of the world's leading general science journals.
Crows have previously shown they can use stick-like tools to manipulate their environment.
They have also been observed dropping nuts on to pedestrian crossings for passing cars to crack open, then waiting for the green man signal so they could collect their nuts safely.
The work was funded by the Marsden Fund.
WHO WAS AESOP?
A Greek writer who lived more than 2500 years ago. He became known for writing fables, or stories with a moral teaching.
Some of his best-known fables include The Tortoise and the Hareand The Boy Who Cried Wolf.
In the fable of The Crow and the Pitcher, a thirsty crow learns to raise the water level in a pitcher by dropping in stones. The tale concludes with the proverb: ''Necessity is the mother of invention.''
- The Dominion Post
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