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
Rutz followed up by watching crows in the wild and saw some do the same thing. He noted that the crows preferred tools from the shrub Desmanthus virgatus, which can be reshaped if flexed past its desired form. Rutz has previously reported that wild crows value their tools so highly they will store them for safe-keeping.
The researchers speculate that a bent tool has advantages because the tool tip can be optimally positioned within the crow’s field of view, while the other end is held in its beak.
So what does this mean for crow intelligence? Rather than on-the-spot problem solving, Betty may have been using a tool technique that went back generations.
However, the idea of New Caledonian crows as avian geniuses doesn’t rest on Betty alone. The capacity to understand Archimedes Principle and to change their social networks when they might learn something new from a peer suggests that their reputation is well earned.
Complicating matters, rooks, a species that do not use tools in the wild at all, have been observed shaping hooks when given wire, suggesting that predisposed behavior is not necessarily the full explanation.
Nevertheless, Rutz claimed: “Our study is a powerful reminder of the importance of basic natural history research,” in order to get an idea of an animal's wild behavior before testing them in the lab.