Video: Crow uses a metatool

The crows had to use a short stick to extract a longer stick from a cage – before using that to get a food treat

New Caledonian crows, famed for their tool-making skills, can also use tools to manipulate other tools. Such “metatool” use shows that the crows have the brainpower to apply their skills to a completely new situation and plan ahead to solve a task, researchers believe.

Working with captured wild crows, Russell Gray and his team from the University of Auckland in New Zealand hid a treat in a box so that a crow could only extract it with the help of a long stick. This kind of task is easy for the tool-using crows.

But then the researchers added a twist by placing the long stick in a cage, out of the crows’ reach. No problem: the birds used a second, shorter stick, to get the first one, then took it back to the box to get the food.


“Six out of seven crows tried straight away to use the short stick to get to the long tool. There was no trial and error,” says Gray.

Cognitive complexity

Metatool use is normally only seen in humans and apes. Even monkeys struggle in similar experiments. This is thought to be due to the cognitive complexity of the task, which requires using a tool on an intermediate object in a novel context before tackling the real goal, which is to extract the food.

Gray believes that the best explanation for such flexible, hierarchical behaviour is that the crows are using “analogical reasoning”, applying previous experience – tool gets food – to solve a novel, but structurally similar problem – tool gets tool gets food.

But Sabine Tebbich from the University of St Andrews in Scotland, who wasn’t involved in the study, thinks that while the crows’ behaviour in this experiment is “truly remarkable”, it is too early to make claims about analogical reasoning, because wild crows tend to use tools to explore their environment.

“We can’t rule out that they have done similar tasks before in the wild,” she says. More experiments are needed to show how the crows are reasoning, she says.

Nathan Emery from the University of Cambridge, UK, however, who recently found evidence for analogical reasoning in the food-hiding behaviour of closely related birds, says the crows probably use similar cognitive skills. “This study shows their ability to plan a few steps ahead and demonstrates another striking convergence between crow and ape intellectual abilities,” he says.

Journal reference: Current Biology vol 17, p 1 (DOI: 10.1016/j.cub.2007.07.057)