Vocal Fry Serves Up Treats For Toothed Whales
Toothed whales—species like orcas, bottlenose whales, and dolphins—use echolocation to zero in on prey about a mile deep into the ocean.
Until now, scientists couldn’t quite figure out how the whales were making these clicking sounds in the deep ocean, where there’s little oxygen.
A new study published in the journal Science, finds the key to underwater echolocation is vocal fry. Although in whales it might not sound like the creaky voice that some people love to hate, the two sounds are generated in a similar way in the vocal folds.
Ira talks with the study’s co-author, Dr. Coen Elemans, professor of bioacoustics and animal behavior at the University of Southern Denmark based in Odense, Denmark.
The three voice registers of a bottlenose dolphin in sequence. First a few echolocation clicks (M0 register), followed by “bursts” in the M1 register and finally a “whistle” in the M2 register. Credit: Coen Elemans, University of Southern Denmark & Peter Madsen, Aarhus University
Calls by a killer whale (Orcinus orca) consistent with three voice registers. First a few echolocation clicks (M0 register), followed by a call and a “whistle” that are probably in the M1 and M2 register, respectively. Credit: Olga Filatova, University of Southern Denmark
Coen Elemans is a professor in Bioacoustics and Animal behavior at the University of Southern Denmark in Odense, Denmark.
IRA FLATOW: I want to end this hour with a story that’s– well, how shall I say– a whale of a tale. Toothed whales– think orca, bottlenose whales, and dolphins– toothed whales use echolocation to zero in on prey deep underwater. And we’re talking about a mile deep or more.
Until now, scientists couldn’t quite figure out how the whales were making those clicking sounds in the deep ocean, where there’s little air. It turns out the key to underwater echolocation is vocal fry. Yeah, that creaky voice that some people love to hate, only this time in a whale. Here’s what it sounds like.
[WHALE VOCAL FRY VOCALIZATIONS]
Here to tell us more about this discovery, published this week in the journal Science, is my guest, Dr. Coen Elemans, professor of bioacoustics and animal behavior at the University of Southern Denmark, based in Odense, Denmark. He’s joining us today from Washington.
Dr. Elemans, welcome back to Science Friday.
COEN ELEMANS: Thank you so much for having me again. It’s great.
IRA FLATOW: Can you begin by telling us exactly what vocal fry is, for people who don’t know?
COEN ELEMANS: Yes, a vocal fry is one of the few human registers. We have at least three, maybe four, where the vocal folds move qualitatively different in each register. And with vocal fry, the movements are such that the vocal folds are basically closed for more than 60% to 80% of the time. So they’re closed most of the time, and then they open very briefly, with a lilt, and then they have a little snap. So a very little bit of air passes through.
IRA FLATOW: So why exactly does vocal fry help toothed whales with echolocation when they are so deep underwater?
COEN ELEMANS: What we’ve been able to show now is that sound production in toothed whales actually occurs in their nose. And by combining a bunch of different experiments, we’ve been able to show that two pairs of phonic lips basically make these echolocation clicks. So these echolocation clicks are made in the vocal fry register.
And one of the cool things of this is that, when whales dive, of course, their volume of air decreases very, very rapidly. And below 100 meters, they only have 10% left. Below a kilometer, they only have 1% left. So they need to be very air efficient. And this vocal fry register allows them to be very efficient with their air.
IRA FLATOW: What are they actually doing in their bodies, in their heads, in the melon?
COEN ELEMANS: When the whales dive, they basically shuttle all the air that’s in their lungs into their nose. And there it goes into a cavity that’s in the skull that cannot be compressed. So the air stays there safely. And then the larynx, which we use to produce sound, lost this function in toothed whales. And it’s become a very efficient plug. So it fits very nicely into this bony nose structure, basically. And that allows them to separate these two compartments, basically. So you have an air compartment in the nose and an air compartment that’s very rapidly declining in the lungs.
So when they dive, the lungs completely collapse and all the air moves into their nose. Now, this allows them to separate the control of these volumes. And that’s been key, I think. So one of the main things they can do is they can have pressurized air in their nose to extremely high pressures without damaging lung tissue. So when we play, for example, trumpets really loud and we try to do it a few times louder, we would actually damage our lungs. And these animals uncoupled these driving pressures, basically, in their nose and in the lungs.
And then the other cool thing they can do is then they can use this very high diving pressures to make the loudest sounds in the animal kingdom, basically.
IRA FLATOW: Hmm. Now, you categorized toothed whale vocalizations into three different registers, similar to humans– vocal fry, which we just talked about; then you have the chest register, normal speaking tone; and the falsetto, even higher than the others. Why did you decide to categorize them in this way?
COEN ELEMANS: It’s actually the other way around. When we realized that this was analogous to normal vocal fold oscillation, we realized that this huge diversity of sounds that these animals make actually fit very nicely in these three categories that are the registers. And then what we did is we tried to– through different lines of evidence– tried to show that this is also the case.
One line is the sound– so you see, indeed, that these animals make– distinct sounds that have different waveforms, but also different frequency ranges, just like registers. Then, also the anatomy supported. And, lastly, we looked at the opening and closing of these vocal folds, first, in vitro, but then later also using tags. We tried to reconstruct the vocal fold kinematics of animals diving down to 2 kilometers deep, based on the sounds that we could record on these tags.
IRA FLATOW: OK. Let’s listen to what these different registers sound like. Let me play, first, the orca, the killer whale.
Dr. Elemans, tell us what we were hearing.
COEN ELEMANS: Yes, at first, you were hearing a few echolocation clicks. And after that, another sound these animals make. And this is definitely in a higher frequency range. And last was what’s called a whistle. And these whistles go even up to 80 kilohertz in killer whales. It’s really spectacular. They have an enormous frequency range they can produce.
I am absolutely sure there’s going to be lots of different sounds that don’t necessarily fit in these categories, but this provides a first physiological basis to start classifying these sounds.
IRA FLATOW: OK. Now, let’s listen to the bottlenose dolphin. It also starts with echolocation, and then the other two registers.
[BOTTLENOSE DOLPHIN VOCALIZATIONS]
Wow. That really doesn’t sound like the vocal fry I’m familiar with in people.
COEN ELEMANS: No. So during echolocation, the frequencies are very low.
IRA FLATOW: Yeah, it’s almost like a hearing test, when they try to see how low you can hear.
I’m Ira Flatow. And this is Science Friday, from WNYC Studios.
This study, I understand, is the culmination of 10 years of research. And in that time, you had to develop some new techniques to study echolocation. How did you study the toothed whales?
COEN ELEMANS: Yeah. Something that was really fun in this study is that we used a lot of different approaches. So first, we developed techniques to film trained animals– so inside, in their nose– with very small endoscopes and fast cameras. That allowed us to show that the source is definitely in the nose. But it also posed a conundrum. Because we saw there was clear motion going on with each echolocation click, but it happened after the click. So that was totally weird.
And what we did then is that we developed a setup that we’ve also used for other species in the lab, where we can blow air through an isolated head. It’s very difficult to study these animals. It took us several years to collect sufficiently fresh animals, basically, that died either in beachings or in fishermen’s nets, to be able to show really phonic lips make the sound.
We also tagged the animals, where you put an acoustic tag on the animal. And we needed to be very precise to have the tag on the nose. And there was also sieving through many, many years of tagged animals.
IRA FLATOW: Now, what did we know and what didn’t we know about how toothed whales make vocalizations before this study?
COEN ELEMANS: So what we definitely knew is that the sounds were produced somewhere in the nose. There was a lot of different lines of evidence. It was very challenging to film them. And so people have tried to film them, but these were at insufficiently high frame rates to actually demonstrate these were the sound sources. But now we’ve established that it’s actually that sound source. And also, the theory we established for human sound production is also applicable here in a completely new organ that’s evolved only in these animals.
IRA FLATOW: This study focused on toothed whales, as we’ve been talking about. What about baleen whales, who also make sounds but don’t use echolocation? What do we know about their anatomy?
COEN ELEMANS: In baleen whales, it’s a similar problem. All the things we know about their sound production are acoustic recordings. And they’re very hard to interpret. Because if you put a hydrophone on the water, you can record animals within several kilometers. So it’s very hard to pinpoint which animal makes what sound. And again, it’s very hard to get fresh tissue there. But we know very little about the functional aspects of those baleen whales as well.
IRA FLATOW: Did they have the same origins, both kinds of whales?
COEN ELEMANS: Both groups of whales evolved from a common ancestor about 40-45 million years ago. And that was an animal that much resembled a hippo. And then at some point, echolocation evolved in these animals. And the toothed whales come out of that group. And the other group became the baleen whales.
IRA FLATOW: So echolocation seems to be the reason why they branched out. Given just how critical vocal fry is to how toothed whales do evolved and hunt for prey, do you think this might change some vocal fry haters to better appreciate its usefulness?
COEN ELEMANS: I really hope so.
I really hope so. It was very funny because I’ve been very much focused on this over the last weeks of course and months. If you listen on airports here, so like, so many people use vocal fry at the start of sentences, at the end of sentences. And it’s not just young women or old women or men. Everybody does it. It’s very common.
IRA FLATOW: Let’s make it official. Let’s call today Science Vocal Fry-day.
COEN ELEMANS: OK. Vocal Fry-day, I like that one.
IRA FLATOW: Great. Dr. Elemans, thank you for taking time to be with us today.
COEN ELEMANS: Thanks so much. Take care.
IRA FLATOW: Dr. Coen Elemans, professor of bioacoustics and animal behavior at the University of Southern Denmark, based in Odense, Denmark.
If you want to listen to those toothed whale vocal fry recordings again, or check out some graphics explaining whale vocal anatomy, sure, go to our website, sciencefriday.com/whalesounds.