Breed of Crow Uses a Tool to Catch Its Grub

(Sept. 16) -- Think you know your way around a toolbox? The New Caledonian crow could give you a run for your money – and it's helping scientists shed light on why an elite group of animals rely on tools to do everyday tasks while most species face the world empty-handed.

The crow, a resident of several islands off Australia, is one of the animal kingdom's best toolmakers. It shapes leaves and branches into skewers that it then pokes at grubs burrowed into tree trunks. The irritated grubs clamp on to the skewer, thereby forming a convenient grub shish kebab.

But grub extraction is an art that's difficult for young crows to master. Even experienced crows can spend half an hour fishing for a grub. So why bother?

In the journal Science, an analysis of the crows' feathers and blood shows that grubs are the crow world's equivalent of the Big Mac. They are so laden with fat and protein that only three grubs provide an entire day's worth of calories.

"The perfect food source," lead researcher Christian Rutz of Oxford University told AOL News.

The discovery is the latest finding in a long-running campaign to understand why some animals use tools and others don't. The answers could help shed light on the evolution of intelligence and on whether tool use played a role in the development of humans.

Many species are known to use tools in the wild, ranging from sea otters -- which use rocks to break open mussel shells -- to the Galapagos woodpecker finches, which fashion cactus spines into levers to pry insects out of their holes. The harder scientists look for tool use among animals, the more they find:

• Some of the dolphins living along the coast of Australia wear sea sponges on their faces as they scout the ocean bottom for food. The sponges help dislodge hidden fish, according to a study published in 2008. Sponge-using dolphins "are able to exploit food that others can't readily access, namely burrowed prey," study author Janet Mann of Georgetown University, explained via e-mail.

• Chimps in the African nation of Guinea use stone and wooden cleavers to chop hard, volleyball-sized fruits into manageable chunks, a team led by Kathelijne Koops of Cambridge University reported last year. The tools are reminiscent of the stone chippers and cutters made by ancient humans, suggesting that the ape ancestor of humans and chimps may have used tools.

• Rooks, which live in Britain and are similar to American crows, don't use tools in the wild, but they quickly made use of tools in the laboratory to reach worms in experiments published by a different Cambridge University team last year. The rooks even figured out how to bend a piece of straight wire to make a hook to grab a worm-laden bucket. So wild rooks can use tools; they just don't need to.

The rooks' adeptness shows that animals that use tools aren't necessarily smarter than those that don't, said Rutz, the New Caledonian crow researcher. The crows he studies have both the motivation to use tools -- the super-rich grubs -- and good luck. They face no competition from woodpeckers and don't have to worry much about being picked off by an eagle or hawk while they fuss with their skewers.

"Maybe this combination [of factors] is so rare that it only occurred several times," Rutz said.

Animals that use tools must have a combination of smarts, bodies that allow them to make tools and the ability to pass their handiness on to their children or other animals, Martha Robbins of the Max Planck Institute for Evolutionary Anthropology told AOL News. But there are other, less tangible requirements.

Gorillas, she points out, are much like chimpanzees. They're both social animals that live in similar habitats and have big brains. Chimps are the world's best tool users, other than humans. Gorillas don't use tools much at all. The reason isn't known, but it may have to do with culture: Different groups simply do things differently. Separate populations of chimps have their own ways of using tools, for example, though Robbins fears some of those distinctions will be lost to science as chimps are killed off in the wild.

"We need more time" to study tool-use culture, she said. "And we need to be able to do this before we lose them."