Crafty Crows Teach Each Other How to Make Tools

October 16, 2015 | Sarah Tse

A New Caledonian crow using a Pandanus tool to dig for treats.
Photo credit: Mark Sibley

Calling someone “birdbrained” will no longer pack quite the same offensive punch, according to a new study on toolmaking among crows.

While we’ve observed many animals repurposing found objects as tools, the ability to create tools from raw materials was long thought to strictly belong to primates. Various primate species have demonstrated their craftsmanship in building tools to acquire food, communicate, traverse obstacles, and even attend to their dental hygiene. Even more remarkably, these primates pass down their technological acumen to each new generation, building up the same sort of cumulative culture responsible for most human achievements.

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But a new study may open up that distinction to include birds — specifically, the New Caledonian crow. These crows fashion tools out of Pandanus leaves by cutting segments out of the saw-toothed edges. They can then use this tool to dig grubs out of logs. Most peculiarly, scientists have observed the birds experimenting with different designs — wide, narrow, and stepped shapes, depending on geography.

To figure out how the crows were transmitting ideas for these different tool shapes, Carina Logan of UC Santa Barbara’s Sage Center for the Study of the Mind devised a study to test the cognition of these crafty crows. She had the crows play with specially designed apparatuses with multiple doors, one of which hid a reward in the form of a hard-boiled egg. This way, crows with more experience using certain tools wouldn’t have any advantage over the inexperienced individuals, since none of them had seen the apparatus before.

The crows exhibited a type of social learning mechanism called stimulus enhancement. After seeing another bird successfully snatch a piece of egg out of a certain door, a second individual would go for the same door and begin figuring out how to open it. But instead of exactly copying the actions of the first bird, this second individual would use a trial and error method to find its own solution — basically, it was inspired by its mentor and set in the right direction.

Logan hypothesizes that in the wild, parents might leave their leaf tools around the nest for the juveniles to play with and learn to use on their own. It is this combination of social learning with individual trial and error that creates the cumulative technological culture.

What’s truly remarkable is that crows do not exhibit the age-ism ingrained in human culture. The groups consisted of different combinations of adults and juveniles, related and unrelated. The crows didn’t care about the age hierarchy; the old learned from the young and vice versa.

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