美国国家公共电台 NPR Crows: Are They Scary Or Just Scary-Smart?（在线收听）

Crows: Are They Scary Or Just Scary-Smart?

MADDIE SOFIA, HOST:

You're listening to SHORT WAVE...

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SOFIA: ...From NPR.

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SOFIA: Hey, everybody. Maddie Sofia here.

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SOFIA: Crows are one of those animals that have been long associated with the spookies (ph). I mean, come on. A group of crows is called a murder. I find them a little unsettling, but not in the Alfred Hitchcock they're-coming-to-peck-your-eyes-out way.

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SUZANNE PLESHETTE: (As Annie Hayworth) Do not make a sound until I tell you to run.

SOFIA: What gets me is just how smart they are.

KAELI SWIFT: You know, we have this expression birdbrained. And that comes from a long history of us believing that birds weren't very intelligent. And it's only been in the last couple of decades that we've come to appreciate just how incredibly smart crows are.

SOFIA: That's Kaeli Swift from the University of Washington. She did her Ph.D. on crow behavior. And today, she's dropping some crow knowledge on us.

SWIFT: We are going to talk about how crows can learn and remember human faces, how they pay attention to their dead and how they make and use tools.

SOFIA: It just might change the way you think about our spooky friends. All right, here we go.

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SOFIA: One of the coolest and kind of unsettling things that I know about crows is that they can memorize faces. Like, tell me how we figured that out.

SWIFT: Yeah, they can memorize faces in both negative contexts, meaning that if you do something bad to a crow, or positive contexts, meaning that if you do something nice for them, like feed them. And the first study that ever demonstrated this was a really simple setup. Basically, they wore these masks, and they trapped crows. They captured wild crows. And, you know, although we obviously take every precaution during that experience to make sure that the bird's safety is at a premium, it's still a scary experience for the bird.

And then - so what they did during that trapping experience is they put these colored bands on their legs, and then they let the birds go. And so the question as far as showing if they remembered faces, all they did to address that was, later, they would send people out wearing that same mask, the ones the birds had seen while they were getting captured. And they looked for how the birds responded to them.

And lo and behold, when they saw that face, they would alarm-call. They would dive-bomb that person. And really importantly, it could be anybody wearing that mask. And, in fact, they even had a mask made that was inverted. it was upside-down. And they found that when they did that, for just a brief moment the crows seemed a little confused, and then they would just tilt their head upside down. And then they'd start alarm-calling.

SOFIA: Ugh (laughter).

SWIFT: So even having the upside-down face didn't throw them. They were like, ah. You're not getting anything past me. I remember that face.

SOFIA: Is it just the crow that got captured, or is it, like, the group of crows knew that that guy was a bad guy?

SWIFT: Yeah, that's a really great question. So it's not just the crows that were captured. And that was a really interesting finding from this study because like I said before - right? - the birds that were captured have these colored bands around their legs, which means that when they would come in to scold this, if there were other birds around - unbanded birds - those unbanded birds, they were coming in and also scolding and dive-bombing this person.

So what that tells us is they were actually learning from their peers that this particular person is dangerous. And we found that that information got spread through the cohort, you know, within the same generation - meaning peers - but that also juveniles, that they were learning from their parents effectively.

SOFIA: So let's say I go, and I'm mean to a crow, which I would never do - too much respect. How long would they know my face?

SWIFT: Years and years...

SOFIA: No (laughter).

SWIFT: ...Is what it seems like the answer is. Yeah, yeah. There hasn't been a published update, so I can't give you, you know, a scientifically specific number. But I think your assumption should be that that bird is going to remember you for a very, very long time.

SOFIA: OK. So you actually did some experiments yourself. And so cool crow fact No. 2 - crows kind of hold funerals?

SWIFT: That is right. So crows are among a pretty small - at least as far as we know now - group of animals that seem to pay really close attention to their dead and then respond really strongly to them. So in a nutshell, what a crow funeral looks like is the first bird that discovers the body will alarm-call.

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SWIFT: So that's that really harsh cawing sound.

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SWIFT: And that sound attracts other crows to the area.

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SWIFT: So then they'll all get together, and they'll be sitting in the treetops or maybe flying around a little bit, producing that alarm call - that scolding call. And then, after about 15 or 20 minutes, they'll disperse and kind of go back to their normal crow business.

SOFIA: Were you thinking that they're basically going to the site of the death and maybe trying to, like, learn what happened? Or what's the mindset?

SWIFT: Exactly. So we knew that they did this behavior. The question for us was, well, why? So we tested two sort of specific ideas relating to that. One was whether or not they learned that particular places associated with dead crows might be bad. And the second is if they learned new predators, specifically people. So basically, if they saw a person holding a dead crow, would they learn that person's face and go, you know, guilty by association. I'm going to assume that you're a predator because I see you with a dead crow.

SOFIA: I see. OK. And then how - what about the - you know, like, whether or not a place was dangerous?

SWIFT: So for that part, what we did is we would feed crows over the course of a couple of days to get them used to coming to a particular area and to gauge how quickly they would come into food. And then we would continue to feed them after the - what we called the funeral moment, where we would send that masked person out holding a dead crow.

And what we found is they never avoided the place altogether. Very rarely did they avoid the place altogether. But it did take them a lot longer to come down to those piles of food than it had previously. And we didn't find that to be the case with our controls. And so that suggests that crows did indeed learn from that experience that, although those Cheetos might be really tempting...

SOFIA: (Laughter).

SWIFT: ...Because there was a dead crow here earlier, I should probably be extra careful before I come down and get my snack.

SOFIA: OK. And what happened when you had a person holding a dead crow, and they had that mask? Did they associate that person with, like, dead crows?

SWIFT: Exactly. So just like in the original facial recognition study, when they would encounter that person later, even though next time, you know, they wouldn't have a dead crow - they wouldn't be doing anything nefarious - they still - right away, they would start in on that alarm-calling. They'd dive-bomb them.

SOFIA: Oh, my God. (Laughter) It's so - it's very fascinating and very unsettling, Kaeli. I'm going to be honest. Last up, crows can use tools. And this is wild to me. Like, I don't necessarily associate birds with making and using tools, but they definitely do that, right?

SWIFT: They do, yeah. And they're basically flying primates when it comes to their intelligence. And there's actually some things that they do better than primates. So like chimpanzees and orangutans, a particular species of crow called the New Caledonian crow can actually make tools. And that's a really important distinction from using tools.

There's a lot of animals that use tools. But modifying a material for a specific purpose - that's much more complicated. And one of the most amazing things that they do in the wild is actually make hooks. And as far as I know, they're the only other animal besides early humans that habitually make hooks in the wild. We've seen it in some primates in captivity. But they basically take twigs to make essentially little fishing hooks that they use to extract bugs and things like that from out of wood.

SOFIA: Wow.

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SOFIA: OK, Kaeli. Thank you so much. That was delightful. I really feel like I respect crows more than I'm afraid of them, maybe. But it's a healthy mix. So (laughter) thank you for talking to us.

SWIFT: Thank you so much. I feel like my work here is done (laughter).

SOFIA: (Laughter) I'm Maddie Sofia, and this is SHORT WAVE from NPR. Join us tomorrow for a special Halloween episode about some of the zombies of the animal kingdom. And hey, if you're an Apple podcast listener and you've been loving us, maybe drop us a review. It really helps us out.

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