Whale Song Is All In The Larynx

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Later in the hour, we’re going to talk with a young researcher studying Parkinson’s disease. And we’ll check in on the current state of our aging nuclear weapons. But first, if you’ve heard recordings of whale songs you know that they can be both beautiful and haunting.

[WHALE SINGING]

Really cool. You know what? The way that baleen whales, like humpback and minke whales– the exact mechanisms whales used to make those noises, we really never understood, that is as they say, until now. A recent study in the journal Nature investigates the mysteries of the whale larynx and its role in whale songs. Joining me to talk about it is Dr. Coen Elemans. He’s a Professor of Bioacoustics and Animal Behavior at the University of Southern Denmark in Odense, Denmark. Welcome back to Science Friday.

COEN ELEMANS: Thanks so much for having me again. It’s always a pleasure.

IRA FLATOW: It’s so nice of you to say that. OK. It’s amazing to me that we didn’t know how whales made those sounds. Why is that?

COEN ELEMANS: Well, it’s difficult for several reasons. So first of all, if you put a microphone or an underwater microphone, which is called a hydrophone, in the water, you pick up sounds from very far away because sound travels so fast and so far in water. And so it’s actually quite difficult to say if you’re recording something that it is a certain animal that is in the area because you see it. It could be coming from 10 miles away or even further.

Since the last 20 years or so, people started to develop tags you can put on a whale. And since then, it becomes easier to actually associate a certain sound with a specific species. So that’s one thing. The other thing is that it’s very hard to study physiology of whales. So first, we’ve hunted them down to near extinction. So they’re all protected now.

And the other thing, when there is a whale that, for example, beaches and dies, then they typically rot so fast when they’re on the beach because you cannot get there fast enough, for example, that actually the tissue is so rotten you cannot see so much from. It or you cannot learn so much from it in terms of physiology.

IRA FLATOW: Well then, what made it possible for you to study them now?

COEN ELEMANS: So we were extremely lucky that we have a very active stranding network in Denmark and also in Scotland where basically, people alerted us to a whale that beached. The first one was in 2018, actually. And it beached in very bad conditions for the whale, of course, but in very good conditions for us close to a harbor– very cold weather, cold water. And so we could get there very fast and get very fresh tissues out.

IRA FLATOW: So you were able to look at the larynx of these beached whales. How similar is a giant whale throat to mine or yours?

COEN ELEMANS: Well, it’s quite different. And that was partly known because people have studied the anatomy for whales for quite a long time, and also the larynx. What is very different is that the little cartilages that move our vocal folds together, and as such allow speech, they are very different in a whale.

They’ve become massive tubes that basically form a U shape, and this U shape is largely immobile. And we think that’s the case because then it opens the airways when these animals have to breathe on the surface. So a massive airflow is coming back and forth when they when they surface and breathe. And if you then have vocal folds sitting in the way, they would start to flap and actually be annoying. You don’t want that.

IRA FLATOW: But they’re underwater, and they make these sounds, which means they still have to blow air through their larynx. How do they do that?

COEN ELEMANS: Yeah. So what we think is that what they do is they still push air from their lungs through their larynx. And this goes into a sac that’s called the laryngeal sac. And this sac collects all the air. And then a big muscle surrounding it pushes it basically back through the larynx, back through the lungs. And this way, they can recycle the same air back and forth without surfacing and actually taking a new fresh breath.

IRA FLATOW: Now, you’re talking about the baleen whales, right? Do the other kinds of whales that don’t have the baleen in them, do they do the same thing?

COEN ELEMANS: No. So actually, last year we had a paper where we showed how the toothed whales– and that involves the dolphins, the killer whales, and for example sperm whales– how they make their sounds. And they evolved completely novel structures that sit in their nose. And so they’ve made a totally different solution to this problem, how do you make sound on the water when you hold your breath.

IRA FLATOW: Wow. OK. So let’s talk about the whale that washed up that you used. How do you go about proving with a dead whale that this is how it makes the sounds? Tell me about your setup.

COEN ELEMANS: Yeah. So first, we studied the anatomy in great detail. We froze these larynges down. We studied their anatomy, and then we built a setup where we basically, in very controlled conditions, can blow air through the larynx. And that’s where you can study the vibrating structures that generate sound. And if the tissue is fresh, then actually, the properties are very similar to in a living whale. And that means that if you get vibrations, they should be the same as what the whale does in vivo. And that’s what we also saw.

So it took a while to build such a setup, not because it’s big, but because it required all kinds of adaptations because the larynges are so huge. And we could measure very accurately things like flow and pressure. And with high-speed cameras, we could film things that vibrate. And we could show that the vibrations were exactly the same frequency as you see in a living whale.

IRA FLATOW: Well, you got to tell me how you MacGyvered this thing.

COEN ELEMANS: Yeah. So it was a nice crossover between MacGyver and scientific research. So we needed a setup where we have very high flows of air with low pressure. And actually, that was a bit complicated. So we ended up using– well, first, we wanted to try weather balloons. That didn’t work. And then in the end, we used party balloons, basically, that have a really big volume and a very low pressure. And then we could let the air out of these things while measuring pressure and flow very accurately. And that powered very accurately the larynges.

IRA FLATOW: Wow. So you had a really close, accurate sound of how the living whales would do it?

COEN ELEMANS: Yeah. So what we can mimic really accurately is the lowest frequencies these animals can make because then the tissues are not so stiff, and they vibrate at that lowest frequency. What we couldn’t do in the lab was to then activate muscles, for example, because the tissue is dead.

And to do that, we made computational models where we basically made a full 3D larynx in a computer– could blow air past it– confirm our first experiments. But then we can also start simulating the activity of muscles, for example. So with these computational models, we could now show how high frequency sounds you could generate with this mechanism.

IRA FLATOW: OK. Lucky for us, you have provided us with some of the sounds you created. So let’s listen.

[LOW FREQUENCY SINGING]

Wow, Dr. Elemans, what are we listening to? What are we hearing?

COEN ELEMANS: So what we’re listening to is actually the acceleration of a part of the vibrating tissue. So it’s made into sound.

IRA FLATOW: That was really low frequency. Wasn’t it?

COEN ELEMANS: It’s very low frequency, yes.

IRA FLATOW: And that’s realistic?

COEN ELEMANS: Totally. Yeah. So this was of a sei whale, and the sei whale makes this very low frequency “mmm” sweeps. And it’s exactly, basically, what these animals do.

IRA FLATOW: And of course, the whales often have these sounds in the higher part, the higher registers. Does your research account for these too?

COEN ELEMANS: Yeah, partially. So all these baleen whales, all 16 species, make very low frequency sounds. And if we looked in detail at the anatomy that is studied in these animals, we see that this cushion where we show now that generates the sound, it’s there. It’s present in all these species. So we think that’s the ancestral state.

But a few species, like the well known humpback, but also bowhead whales, for example, they are very well known for their song that’s very high frequency. And so how do they do that? And what we now found is that actually the arytenoid cartilage is this big U shape. In these species, we’re able again to come together. And so again, it looks a little bit like human vocal folds. And that makes, again, definitely sound. And we think that’s what mechanism is responsible for these very high frequencies in those species. That we were not able to show because we couldn’t simulate that in the lab.

IRA FLATOW: I see. Of course there is a big variation in the human vocal range. You’ve got James Earl Jones on one side, and you have an opera soprano on the other. Do whales have a similar range like that?

COEN ELEMANS: Well, actually, I wouldn’t know. We don’t know enough yet about how individuals perform. So we have tagged individuals and can see what they can do. But there’s lots of mysteries out there. I talked to a colleague last week. And for example, a few of the whale species seem to go lower and lower and lower in frequency over the last years. And everybody’s really puzzled how this could work. And so there’s lots of open questions there.

IRA FLATOW: Your research says that there are some sort of limits on how and where whales can sing. Is that correct?

COEN ELEMANS: Yes. So we show now that this U shape against the cushion mechanism is limited in frequency range. So first, it’s really cool because it allowed the whales to make sound while holding their breath on the water. And it allowed them to live, basically, and evolve. But it also is very limited, and it limits them to, probably frequencies of, let’s say, 5 hertz to 300 hertz. So that’s one limit.

Another limit is that we could now measure how much air they need actually to make these vocalizations. And because we can estimate the amount of air available in a whale, and also scaling with size and so on, we could estimate how deep can you now take, basically, the system and still have enough volume to make a sound.

When we did these simple models, we basically showed that about 100 meters or so deeper than that, the whales they don’t have enough air to basically make sounds. So there is a frequency range and also a depth range where these animals are able to make sound. It depends on how long the vocalization is. But we estimate at about 100 meters, this doesn’t work anymore.

IRA FLATOW: That’s not far down, is it?

COEN ELEMANS: It is for us. It’s very far down, but for a whale, it’s really not. It’s really the surface of the ocean. And a lot of whales can dive much deeper. so we really now give a constraint that the vocalizations are mostly restrained to the surface.

IRA FLATOW: So when they want to talk to each other or vocalize, they have to come closer to the surface to do that?

COEN ELEMANS: Yes, so that’s what we predict. And that’s also consistent with the data that people are getting from these tags where you put a tag on a whale. And those animals typically sing below 20 meters, actually, or even shallower.

IRA FLATOW: And what about boat noise? Does that overlap with the sounds the whales are making?

COEN ELEMANS: Yes, absolutely. Actually, the recording you just played of this whale in the lab really reminds you of a boat, right? And that’s also one of the big problems. So now, that range we show where the animals are able to communicate is exactly or very tightly overlapping with the range where we make most noise on the water, or a lot of noise on the water and particularly shipping noise.

IRA FLATOW: So they can’t sing higher to be heard over the boats then?

COEN ELEMANS: There is limitations, physiological limitations, to how loud you can sing, basically. That’s one, and now we also show there’s a limitation to the frequency range and the depth. So all these three together are physiological limitations to these animals.

IRA FLATOW: OK. As I wrap up here, tell me, what more do you want to know about this?

COEN ELEMANS: Well, one thing that’s really open still is how the humpbacks, male and also female humpbacks, make these very high frequency sounds. That would be really fun to figure out.

IRA FLATOW: Well, I want to thank you for coming back and keeping us informed about whales.

COEN ELEMANS: Thank you so much. Take care.

IRA FLATOW: It’s always a pleasure to talk to you. Coen Elemans is Professor of Bioacoustics and Animal Behavior at the University of Southern Denmark in Odense, Denmark.

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