The science section of yesterday’s New York Times has a piece about New Caledonian crows (Corvus moneduloides) by the ever-readable Natalie Angier. She highlights their remarkable intelligence, manifested in their ability to make tools:
In the complexity, fluidity and sophistication of their tool use, their ability to manipulate and bird-handle sticks, leaves, wires, strings and any other natural or artificial object they can find into the perfect device for fishing out food, or fishing out second-, third- or higher-order tools, the crows have no peers in the nonhuman vivarium, and that includes such textbook dexterous smarties as elephants, macaques and chimpanzees.
Videos of laboratory studies with the crows have gone viral, showing the birds doing things that look practically faked. In one famous example from Oxford University, a female named Betty methodically bends a straight piece of wire against the outside of a plastic cylinder to form the shape of a hook, which she then inserts into the plastic cylinder to extract a handled plug from the bottom as deftly as one might pull a stopper from a drain. Talking-cat videos just don’t stand a chance. [JAC note: I object to this last sentence. Angier probably hasn’t seen Maru jump into a box.]
These crows are the only animals known to make tools from stuff they haven’t previously encountered in nature. Here’s crow Betty extracting a plug from a tube. At about 22 seconds she realizes that she isn’t going to get the object with a straight wire, and bends it into a hook around the tube. Amazing!
Why are these crows the most adept tool-makers of all animals besides humans—and that includes other primates? Angier highlights two new papers explaining the theories (I confess that I haven’t read ’em yet). These include an enlarged brain (typical of corvids), a beak seemingly adapted to manipulate natural objects, and a social system with a long enforced “childhood” (juveniles stay with the parents for up to two years), promoting the acquisition of tool use by learning from parents and siblings.
The juveniles need their extended apprenticeship. “They’re incredibly persistent, wildly ripping and hacking at Pandanus leaves, trying to make it work,” said Dr. Holzhaider, “but for six months or so, juveniles are no way able to make a tool.”
The parents step into the breach, offering the trainee food they have secured with their own finely honed tools. “By seeing their parents get a slug out of a tree, they learn that there’s something down there worth searching for,” she said. “That keeps them going.”
They even have local toolmaking “styles”:
The birds are indefatigable toolmakers out in the field. They find just the right twigs, crack them free of the branch, and then twist the twig ends into needle-sharp hooks. They tear strips from the saw-toothed borders of Pandanus leaves, and then shape the strips into elegant barbed spears.
With their hooks and their spears they extract slugs, insects and other invertebrates from deep crevices in the ground or in trees. The birds are followers of local custom.
Through an arduous transisland survey of patterns left behind in Pandanus leaves by the edge-stripping crows, Gavin Hunt of the University of Auckland determined that toolmaking styles varied from spot to spot, and those styles remained stable over time. In sum, New Caledonian crows have their version of culture.
Corvids are amazing birds (the family Corvidae includes crows, rooks, ravens, jays, and magpies). If you want to read more about their smarts and skills, by all means get a copy of Bernd Heinrich’s Ravens in Winter, describing his experimental and observational studies of ravens (in the same genus, Corvus, as crows) at his New England cabin in winter. It’s a great book for biology-lovers.
Here’s a cool seven-minute video showing the intelligence of these birds when faced with a perplexing laboratory situation. They seem to be able to understand concepts, and transfer that understanding to novel situations. Even nonhuman apes can’t do what these crows do!
And I can’t resist adding this David Attenborough video of Japanese crows dropping nuts on the street to crack them, using the cars to do the job. He claims (and this is unbelievable) that the crows actually drop the nuts at pedestrian crossings, so that they can retrieve the cracked nuts when the light turns red! (Just click on the “Watch on YouTube” line.)
Want more videos showing corvid smarts? Here’s a great one from the BBC.