Why Are These Crows So Good With Tools?

New Caledonian crows are among only a handful of species that have been shown to use tools. They use twigs to fish out beetle larvae from dead trees. Reporting in Science, Christian Rutz and colleagues explore why the birds evolved this rare trait.

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IRA FLATOW, host:

I'm Ira Flatow. This is SCIENCE FRIDAY, from NPR.

Joining me now is Flora Lichtman. Hi. Flora's here with our Video Pick of the Week.

FLORA LICHTMAN: Hi, Ira. Happy SCIENCE FRIDAY.

FLATOW: Happy SCIENCE FRIDAY today, thank you. Now, you've got a very - another nice video. I don't want to give it away. Tell us what you have in our Video Pick of the Week today.

LICHTMAN: It's a good animal tale.

FLATOW: Mm-hmm.

LICHTMAN: Let me the scene for you.

FLATOW: Set the scene.

LICHTMAN: Imagine you are a New Caledonian crow, which looks a lot like a regular crow, but you happen to live on the island of New Caledonia, which is pretty good. It's in the south Pacific.

FLATOW: Mm-hmm.

LICHTMAN: Life is pretty good, and you're a little bit hungry. And your bird friends are confined to eating nuts and fruit that they have to find on the ground. But you, because you are this special crow, have a very unusual trait, an unusual ability: You can use tools to get your food. Well, not you.

FLATOW: Well...

LICHTMAN: A New Caledonian crow can. You probably can, too, Ira.

(Soundbite of laughter)

FLATOW: That's right.

LICHTMAN: But the story is how these crows use sticks to pull out these juicy, long-horned beetle larvae.

FLATOW: They're like this super food for them...

LICHTMAN: Yeah. So...

FLATOW: ...like the gourmet food for a crow.

LICHTMAN: I mean, I think it's more like the Power Bar, the Snickers for a crow. They're really high in fat, and they've got a lot of protein, too. And that's what this new study was about this week in the journal Science. Christian Rutz and his colleagues wanted to understand why these crows have this ability that almost no other species in the, you know, in the animal kingdom...

FLATOW: Right. Right.

LICHTMAN: ...have. Like, why do these crows...

FLATOW: They're not primates, not like apes and us, who can use little sticks. But they can.

LICHTMAN: But they can. And so the question was: What's so good about these larvae? You know, maybe the crows that can get the larvae out of the trees have some advantage.

FLATOW: Mm-hmm.

LICHTMAN: And so they looked at the dietary impact of the larvae and found that, in fact, maybe two or three of these larvae a day covers all of the crow's energy needs.

FLATOW: So that's their motivation, then?

LICHTMAN: Right.

FLATOW: And you have it on our website at sciencefriday.com, our Video Pick of the Week is you can watch these crows put some sticks in their mouths - in their beaks...

LICHTMAN: In their beaks.

FLATOW: ...thank you, in their beaks, and poke in to pull out these larvae out of a tree.

LICHTMAN: And the most amazing part of the footage that the researchers provided was not just watching the crows pull them out, but watching the larvae point of view. So they put a larva in a glass cylinder...

FLATOW: Mm-hmm.

LICHTMAN: ...and filmed the crow poking in. And you watch the larva open its mandibles, because the way this works - it's not exactly fishing. They don't skewer them...

FLATOW: Right.

LICHTMAN: ...like a kebab. They actually just irritate them to the point where the larvae open their mandibles and grab onto the stick because they're so annoyed, and then get yanked out.

FLATOW: It's a great video, our Video Pick of the Week...

LICHTMAN: Very dramatic.

FLATOW: ...at sciencefriday.com. You know, you feel like you're Jane Goodall all over, watching these crows.

LICHTMAN: Yeah, it's true. I mean, I think one of the neat things about the footage...

FLATOW: Yeah.

LICHTMAN: ...is that you have access to the crows in a way you didn't before. So another piece of footage where these crow cams, where they actually attached cameras to the tails of crows, which are kind of funny because you've got a through-the-legs shot, which is a little bit awkward, I think...

FLATOW: Right.

LICHTMAN: ...but you see them in flight and you see them sort of going about their daily business.

FLATOW: And it just - it's so shocking that - you know, I've seen crows pick things up off the ground and - a watch or a golf ball or something like that, but I never realized that they could actually put a tool in their mouth and use it all the time without being taught how to do that.

LICHTMAN: Right. I mean, even the crows in the lab that have never - you know, who've been raised in the lab, will use tools and bend tools and make them. I mean, it really makes you think about what it means to be a tool user. Christian Rutz said...

FLATOW: Right.

LICHTMAN: ...that a lot of people were like, wow, these crows must be really super smart. And he said, you know, actually, maybe it's just - lots of animals can do amazing things, thanks to evolution.

FLATOW: Mm-hmm. So if you thought that crows didn't know how to use tools, nevermore think that way. I had to work that...

LICHTMAN: Work it in.

FLATOW: ...Edgar Allan Poe line in.

LICHTMAN: Hey, you just stole the literary reference thunder.

(Soundbite of laughter)

FLATOW: Shucks. I'm sorry about that. And so there's our Video Pick of the Week up there on our website. Flora Lichtman, our digital media editor. Thank you.

LICHTMAN: Thanks, Ira.

FLATOW: See that up there. It'll be up there all week at sciencefriday.com.

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