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In Jean de La Fontaine's fable "Le Corbeau et le Renard" (The Crow and the Fox), it's Mr. Crow who plays the fool, tricked into dropping his morsel of cheese because of flattery from crafty Mr. Fox. However, if de La Fontaine had known about some eye-opening recent research, he might have switched their roles. Crows, it seems, are nobody's fools.
It turns out that New Caledonian Crows not only use tools, as do many of their corvid cousins, but are the only animals other than humans who spontaneously make and use hooks. Although our ancestors started crafting stone tools more than 2.5 million years ago, it wasn't until about 25 thousand years ago that humans started to make hooks--initially for fishing. Recent research shows that human children younger than age 8 rarely come up with the idea of fashioning a hook to retrieve a reward.
Our closest animal relatives, chimpanzees, also use tools, including hook-shaped twigs, and adult orangutans will make hooks to fish for a reward. However, unlike the New Caledonian Crows, which use their claws and sharp beaks to carefully shape and trim twigs into deep hooks, chimpanzees don't modify the hook-shaped twigs they use. "We have recently discovered that chimpanzees routinely use naturally-hooked stems to fish for algae," says primate expert Christophe Boesch, "but they don't actively craft these hooks. The crows can reshape plant material with their pointed bills, which act like 'precision pliers', but this would be very difficult for chimpanzees with their large fingers."
The extra skill and effort the crows put into crafting their hooks pays off in how efficient they are at snagging bugs. "We suspected that tools with pronounced hooks are more efficient, and were able to confirm this in controlled experiments with wild-caught crows," says Christian Rutz, who led this research and has been studying New Caledonian crows for ten years. "The deeper the hook, the faster birds winkled bait from holes in wooden logs." The researchers found that the hooked tools allowed crows to catch their prey two to ten times faster.
A month or two ago I saw a plain old American crow fly up to the peak of a multi-story building, land, and then let something drop from its beak. It turned out not to be a morsel of cheese but a walnut, which rolled down the slanted roof, picked up speed as it fell, and cracked open when it hit the pavement. The crow flapped his way down and snacked on the now-available seed. At the time I thought that this Mr. Crow must have dropped his prize by accident. But now, after reading this research report, I'm willing to bet it was quite deliberate. Their brains may be small by our standards, but crows, it seems, make very good use of them.
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You can find a link to the research report in Current Biology here.
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It turns out that New Caledonian Crows not only use tools, as do many of their corvid cousins, but are the only animals other than humans who spontaneously make and use hooks. Although our ancestors started crafting stone tools more than 2.5 million years ago, it wasn't until about 25 thousand years ago that humans started to make hooks--initially for fishing. Recent research shows that human children younger than age 8 rarely come up with the idea of fashioning a hook to retrieve a reward.
Goin' fishin'--a New Caledonian Crow uses a hook to snag insects
Credit: James St. Claire
Our closest animal relatives, chimpanzees, also use tools, including hook-shaped twigs, and adult orangutans will make hooks to fish for a reward. However, unlike the New Caledonian Crows, which use their claws and sharp beaks to carefully shape and trim twigs into deep hooks, chimpanzees don't modify the hook-shaped twigs they use. "We have recently discovered that chimpanzees routinely use naturally-hooked stems to fish for algae," says primate expert Christophe Boesch, "but they don't actively craft these hooks. The crows can reshape plant material with their pointed bills, which act like 'precision pliers', but this would be very difficult for chimpanzees with their large fingers."
Chimpanzee using a twig to fish for termites
Credit: Valerie
The extra skill and effort the crows put into crafting their hooks pays off in how efficient they are at snagging bugs. "We suspected that tools with pronounced hooks are more efficient, and were able to confirm this in controlled experiments with wild-caught crows," says Christian Rutz, who led this research and has been studying New Caledonian crows for ten years. "The deeper the hook, the faster birds winkled bait from holes in wooden logs." The researchers found that the hooked tools allowed crows to catch their prey two to ten times faster.
A month or two ago I saw a plain old American crow fly up to the peak of a multi-story building, land, and then let something drop from its beak. It turned out not to be a morsel of cheese but a walnut, which rolled down the slanted roof, picked up speed as it fell, and cracked open when it hit the pavement. The crow flapped his way down and snacked on the now-available seed. At the time I thought that this Mr. Crow must have dropped his prize by accident. But now, after reading this research report, I'm willing to bet it was quite deliberate. Their brains may be small by our standards, but crows, it seems, make very good use of them.
-----
You can find a link to the research report in Current Biology here.
-----
If you enjoyed this post, please sign on to follow or receive email notices from zerospinzone.blogspot.com.
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