Crow Tools: Hatched to putter

New Caledonian crows are the first vertebrates to be shown definitively to have an instinctive tendency to make and use tools, contend researchers who doubled as bird nannies.

THE NATURAL. A hand-raised young crow uses a twig to poke food out of a slot without ever having seen the trick before. R. Toft

Two crows hand raised without seeing twig use spontaneously started using sticks to poke food out of crevices, says Benjamin Kenward of the University of Oxford in England. These untutored birds employed the twigs as competently as did two other crows that Kenward coached in twig poking.

One of the untutored birds also spontaneously made a crude version of a leaf tool that the species makes in the wild. Kenward and his colleagues report on their young crows in the Jan. 13 Nature.

“This is the first time we know for sure that a vertebrate has an inherited predisposition to manufacture tools,” Kenward says.

Several birds, such as woodpecker finches and burrowing owls, routinely use tools. They and the other handy species may act on inborn urges, says Kenward, but proving it by raising young animals away from any exposure to tool use is difficult and time-consuming.

The New Caledonian crow (Corvus moneduloides) is one of the few animal species known to not only use tools but also make them routinely. For example, the crows tear strips off Pandanus leaves, making jagged edges (SN: 3/22/03, p. 182: Techno Crow: Do birds build up better tool designs?).

Kenward and his colleagues decided to test for innate manufacturing capabilities when crows brought to England were having trouble incubating their eggs. Kenward gave up much of his normal life for months to foster four little crows.

He gave two of them twig lessons several times a day. A video shows him dragging a stick through a crevice as a young crow clamps its beak on the twig, as if helping.

Even though the other two birds never saw other birds or Kenward use twigs, they spontaneously picked up sticks and poked at food placed in a slot. One of them ripped a strip of Pandanus leaf into a food poker but didn’t create a jagged edge.

Gavin Hunt of the University of Auckland in New Zealand says that he’s not surprised by Kenward’s finding. Keepers at the Noumea Zoo in New Caledonia have told him that one of their crows spontaneously began using stick tools, says Hunt.

However, he proposes that learning from elders also contributes to the use of sophisticated tools in the wild. Geographic patterns of tool design suggest that crows have improved their technology, much as people have, by building on the work of earlier generations, he says. The new study “fits perfectly” with this idea, he adds.

Kenward agrees and even speculates that people’s ancestors might have had a crowlike propensity for toolmaking.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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