Wire-Bending Crow Just Doing What Comes Naturally

Stages in the process of bending twigs into hooks in the wild. Rutz et al/Royal Society Open Science

A paper has put into context one of the most famous animal intelligence experiments of all time, showing that what looked like problem solving may have been natural behavior.

In 2002, a New Caledonian crow (Corvus moneduloides) named Betty bent a piece of garden wire into a hook so she could lift a small bucket baited with food up a tube from a spot she could not otherwise reach. The news went around the world, as it was the first time a bird had been seen bending material to turn it into a better tool.

Convinced that this was an example of problem solving on the wing, animal researchers deemed the example as evidence that New Caledonian crows had a level of intelligence previously unseen in birds. Harder and harder tests were given to the South Pacific birds, including some that would challenge many humans

However, Dr Christian Rutz of St. Andrews University has cast doubt on this wonderful story. In Royal Society Open Science, he shows that bending twigs into hooks is something New Caledonian crows do in the wild, suggesting the problem was not so far from Betty’s experience as had been thought.

“We had provided wild-caught crows with juicy treats hidden in wooden logs, as well as with their preferred plant material for tool manufacture. We were absolutely over the moon when the birds started making and using tools in our field aviaries,” Rutz said in a statement.

Then, however, one of the birds went a little too far, bending a twig tool even though such bending wasn't required to extract the food.

“We couldn’t believe our eyes,” Dr Rutz said. “Most birds trapped sticks underfoot before bending the tool shaft by bill, but one also pushed tools against the logs to flex them, and another wedged them upright into holes before pulling the shaft sideways, just as Betty had done. It turns out, the twigs that wild crows select for making their tools are pliable!”


a) Betty bending a wire in one of the first examples observed of New Caledonian crows' capacity to adjust tools. b-d) temporarily captive crows demonstrating their tool-making techniques. AAAS/Rutz et al/ Royal Society Open Science

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