Squirrels Mimic Bird Alarms To Foil The Enemy It can take more than just a keen ear to figure out what animals are saying. Sometimes, scientists are learning, you have to talk back to map the rich networks of conversation in a forest.
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Squirrels Mimic Bird Alarms To Foil The Enemy

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Squirrels Mimic Bird Alarms To Foil The Enemy

Squirrels Mimic Bird Alarms To Foil The Enemy

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STEVE INSKEEP, HOST:

We've been profiling scientists who explore natural world by listening to it. We call it Close Listening: Decoding Nature Through Sound. Some scientists find they need to do more than just listen. NPR's Christopher Joyce and audio producer Bill McQuay of the Cornell Lab of Ornithology introduce us to scientists who learned to capture what animals are saying and even talk back to them.

BILL MCQUAY: The invention of the phonograph record was a big deal for bird scientists. They could record birdsong and then sit down and really listen - figure out how they communicate - sometimes, anyway.

(SOUNDBITE OF ARCHIVED RECORDING)

ARTHUR ALLEN: This is March 1, 1946.

MCQUAY: That's Arthur Allen from the Cornell Lab of Ornithology. Allen was the lab's founder and one of the nation's leading birders.

(SOUNDBITE OF ARCHIVED RECORDING)

ALLEN: We're set up on a shore of Mattamuskeet Lake, N.C., recording the whistling swans. Another cold, windy morning, and the recorder is apparently not working quite right. And the needle is jumping, perhaps on account of the cold.

MCQUAY: He was trying to actually cut an acetate record of singing birds.

CHRISTOPHER JOYCE, BYLINE: Fortunately, the technology got better and a bit more portable. Let's fast-forward 45 years.

(SOUNDBITE OF ARCHIVED BROADCAST)

TED PARKER: Up here in the canopy, there's another flock. These are the hardest birds to detect.

JOYCE: It's 1991, and that's Ted Parker from a field recording of an NPR radio expedition story in the Bolivian rainforest. Parker was an ornithologist with Conservation International. He spent months at a time in the tropics lugging around a portable tape recorder. He had a legendary skill for using his ears.

(SOUNDBITE OF ARCHIVED BROADCAST)

PARKER: My parents bought me records of bird recordings that were made by people at Cornell. I can remember hours and hours, you know, just putting the needle back and forth, back and forth. And my mother would say, you know, you're going to destroy the record player.

JOYCE: Parker memorized the sounds of over 4,000 bird species. He used his tape recorder to do some of the most extensive bird surveys in the tropics.

PARKER: These birds would spend all their time in that foliage that's 130, 140 feet above the ground. If you don't know their voices, you - there's no way you could come up with a good list on the canopy species.

JOYCE: But Parker wanted more than lists. He wanted know how birds divide up their territory. How do you do that when you can't see them?

MCQUAY: Here's how - mating pairs of birds each have their own territory. Parker hit on the idea of provoking mating pairs to reveal themselves and their patch in the forest. He would record a mating pair. Then, he'd play their song back to them. The birds were confused. They thought it was a threatening outsider.

PARKER: The other thing is if you're outside the territory and you play back the songs, the birds will come up to the edge of their territory.

JOYCE: And they'd vocalize, in essence shouting, hey, get out of here.

(SOUNDBITE OF BIRDSONG)

PARKER: It's antiphonal duet, where the male and female singing different songs. It's the territorial display.

What I do is try to rouse them all. So that I'll actually get a pair here, a pair there, a pair behind me, and you can map all the territories in the forest eventually.

MCQUAY: Parker was doing just such a bird census in Ecuador when he died in a plane crash in 1993. He was just 40 years old.

JOYCE: Years later, a biologist using a similar technique discovered something no one had imagined - how these bird warnings are adopted and passed on by completely different kinds of animals. At his lab at the University of Montana, biologist Erick Greene explains how it works. A small bird sees danger - let's say a hawk or an owl flying around. It warns other birds by making a seet call.

ERICK GREENE: Because it sounds like this. (Imitating seet call).

JOYCE: Then there's a mobbing call. Greene demonstrates by pressing his lips to the back of his hand.

GREENE: (Imitating mobbing call).

JOYCE: Birds make that call when they see a perched predator. It brings other birds out of the trees to mob the predator and chase it away. Now, Greene had watched birds do this for years. Then one day, he noticed something, well, squirrelly.

MCQUAY: We mean that literally.

JOYCE: He realized that squirrels seemed to be mimicking these warning calls from birds as soon as they heard them, almost exactly, even with a totally different vocal apparatus, and chipmunks did it, too. Greene was astonished that mammals and birds would share this early warning system.

GREENE: We've got these complex - what we call communication networks, and it's not just one species yakking to members of its own kind. It's all these different species - not only of birds, but mammals, as well - and they're all sharing information.

JOYCE: Being a scientist, Greene had to observe this happening to be sure of it. At his lab, he shows me how he does that.

GREENE: Let me take you down the hall, and I'll show you some more of our robo-raptors.

JOYCE: Robo-raptors - mechanical birds of prey.

GREENE: And so this is going to be a robo-pygmy owl.

JOYCE: Greene holds a dead owl. It's stuffed with small motors and a computer board that make it move. These are Greene's villains. He takes them into the forest to set off this alarm system.

MCQUAY: I went with Greene to the woods near Ithaca, N.Y., to see how he uses those robo-raptors. He has to hide them at first, inside a fake trunk three feet high. He can then raise and lower the trunk with a remote control.

GREENE: So this is neat, see? We've walked out with this fake tree trunk. Underneath it is hidden a robotic owl, so we're going to be able to lower the tree trunk down with the garage door opener when we're back here, exposing this little robotic owl. And so then then we'll be really interested to see how these birds respond to a predator.

MCQUAY: A few days later, Greene's team had everything in place. They exposed the robo-raptor. It didn't take long before a tufted tit mouse spotted it and started the mobbing call.

(SOUNDBITE OF MOBBING CALL)

MCQUAY: Then, a white breasted nut hatch joined in, then, house sparrows. And if that wasn't enough, the jays chimed in. And just as Greene has now observed numerous times, the squirrels got into the act. It's a madhouse.

JOYCE: Birds, squirrels, chipmunks - and they all propel these warnings through the forest at, says Greene, 100 miles an hour.

GREENE: It's almost as if there's a bow wave preceding the raptor. So in many ways, I've come to appreciate that it's hard to be a hawk.

MCQUAY: Close listeners like Greene are, in a way, hearing the world as other animals do...

JOYCE: ...And finding that it's a world in a constant state of negotiation, across species, everywhere there's life. I'm Christopher Joyce, NPR News.

MCQUAY: And I'm Bill McQuay.

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