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Crow Makes Wire Hook to Get Food

Robert Winkler
for National Geographic News
August 8, 2002
 
The New Caledonian crow is one of the few birds that probes for food with twigs, a form of tool use. Now, three Oxford University, England researchers have discovered that one such crow, a captive female, has gone a step further.

To obtain out-of-reach food, the crow repeatedly took a piece of straight wire and bent it to create a hook. According to the researchers, who report their findings in the August 9, 2002 issue of Science, this behavior suggests that New Caledonian crows "rival nonhuman primates in tool-related cognitive capabilities."

New Caledonian crows living in the wild do create hooked probes from twigs, but the captive crow did something very different.

"To our knowledge, there are no confirmed reports of any animal making a hook out of unnatural material, such as wire, to solve a new problem," said Alex Kacelnik, a behavioral ecologist who coauthored the report with Alex A. S. Weir and Jackie Chappell.




"The surprising thing about our crow is that, faced with a new problem, she worked out a new solution by herself," said Kacelnik. "In the wild, New Caledonian crows make hooks by working on twigs, but they live in social groups and follow age-old techniques in response to problems that the species may have been exposed to for thousands of years."

The crow, named Betty, was caught as a juvenile in Yaté, New Caledonia in March 2000. Since then, she has shared a large indoor room and a small outdoor aviary with Abel, a male brought to the laboratory in Wytham, Oxford after spending ten years in a New Caledonia zoo. A hatchway leads from the indoor room to a testing area.

Betty's toolmaking abilities came to light by accident during an experiment in which she and Abel had to choose between a hooked and a straight wire for retrieving small pieces of pig heart, their favorite food. When Abel made off with the hooked wire, Betty bent the straight wire into a hook and used the tool to lift a small bucket of food from a vertical pipe. This experiment was the first time the crows had been presented with wire.

The researchers then devised a new experiment to test Betty's startling behavior systematically. They placed one piece of straight garden wire on top of the tube and waited for either crow to try retrieving the food. In her ten successful retrievals, Betty bent the wire into a hook nine times. Abel retrieved the food once, without bending the wire.

Betty almost always tried to get the food with the straight wire first. She then made hooks of varying shapes by wedging one end of the wire into taped-up sections of the tube apparatus and tray, or by holding it in her feet, while pulling the other end with her bill.

The researchers say that Betty's creation of hooks cannot be attributed to the shaping or reinforcement of randomly generated behavior. And since she had no other crows to model, no training with pliant objects, and very limited prior experience with wire, they see her actions as novel and purposeful.

"To solve a new problem, she did something she had never done before," said Kacelnik. "Naturally, she must have exploited abilities she acquired doing other tasks in the past, but she showed the capacity to solve a new problem in a creative way by reorganizing her experience."

In their Science article, the researchers point out that Betty's accomplishment—purposefully modifying objects into tools without prior experience—is almost unknown in the animal world. The article cites an experiment in which chimpanzees failed to straighten a length of piping, and pass it through a hole to retrieve an apple, until they were coached.

For Kacelnik, Betty's use of creative problem-solving based on past experience may be evidence of inferential reasoning. Some scientists, he said, believe that even apes lack this capability.

"We do not yet know how far Betty and her fellow New Caledonian crows go in this direction, but this particular case is tantalizing," said Kacelnik. "We are very curious to learn the extent and nature of the cognitive adaptations that allow this. It may turn out that these crows are also better than other species of related organisms at solving tasks not involving tools. We are working on it."

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