Scientist says we’ve got whale song all wrong

When Eduardo Mercado first heard a humpback whale sing, he was fascinated by their rhythmic, moaning, haunting sounds.

Mercado is a bioacoustician — a scientist who studies the sounds that animals make, and he wasn’t convinced that the humpbacks’ songs were mating calls, as many scientists believed at the time.

Instead, he wondered if they might be using their songs as sonar, echolocating the way toothed whales like dolphins are known to do. This set him down a lifelong path to try and figure out just what all their singing actually means.

Mercado, a professor at the University of Buffalo’s department of psychology, has put his decades of research into a new book called Why Whales Sing. This is part of his conversation with Quirks & Quarks host Bob McDonald.

What exactly constitutes a whale song? 

Whale songs are not quite like human songs or bird songs, in that they don’t have a start and stop. If you record the very large whales — the baleen whales, which include the humpback whale — if you record them when they’re singing, they’ll keep on making sounds continuously for multiple hours, in many cases. And if you monitor what they’re doing, you’ll realize that they’re cycling through a fixed sequence of patterns. But there’s not a clear beginning or end. It’s more like an acoustic carousel, where they’re always going around in the same order.

You argue in your book that whales don’t actually sing the way we humans think of the term. What do you mean by that? 

Historically, since the 1970s, researchers believed that what whales are doing is essentially the same thing as what birds do when they sing, which is produce a performance that other animals can listen to and judge the quality of the singer.

What I’m proposing in this book, which is what I’ve been proposing for a while, is that what scientists have been calling songs are actually a sophisticated form of echolocation, similar to what bats do, but over a much broader spatial scale. So the whales aren’t performing for other whales, but are actually exploring, to generate their own internal view of what’s happening around them.

Why do other scientists think the songs are actually courtship rituals?

There’s multiple reasons why people are convinced that that’s what’s happening. I would say the number one reason is that most humpback whales that have been sexed while singing were males, so there’s this sexual difference. They’re often singing in contexts where breeding is happening, so it definitely has something to do with sexual reproduction. And then just the complexity of it, makes them think that it has to be some kind of display, like a peacock’s tail.

Why didn’t that idea resonate with you?

I was analyzing the sounds within songs. And I noticed after analyzing songs from about a decade that had been recorded before I’d ever started, that the sounds they were using were changing over time, from year to year, in a way that if you if you’ve made an alphabet of the sounds they used in say, 1992, that alphabet would no longer apply in 2000.

And that seemed weird to me because no other mammals were doing that, and birds definitely were not doing it. It’s like a peacock’s tail that changes every year. And I didn’t understand how this would be judgable by other whales if there wasn’t always something constant about it that would allow you to say, this is the best kind of song you could produce.

So what led you to believe that it could be sonar?

I was studying dolphin echolocation at the time. And I read some studies of belugas which, when they echolocate, typically do the normal dolphin echolocation by producing clicks and getting the echoes back. But if you have them echolocate things that are really far away from them, they switch to a different mode of echolocation, these little bursts of clicks. I was like, oh, so if you’re going to echolocate things that are very far away, you need to do something different from the norm. 

When the whales are singing, they’re by themselves, and almost always they’re not moving.– Eduardo Mercado

And then I started looking for additional evidence of animals who are echolocating far away, like bats, and discovered that they were doing things very similar to what the whales were doing and in very similar contexts, and then looking to see what the implications of that would be. And, I did some experiments looking at the physics of it, whether it would be possible for a whale to detect, say, another whale that’s two kilometres away using their song, and it worked out physically. 

How did you study the whale’s sonar abilities throughout your career?

So there’s multiple ways I’ve been attacking it. The first was just analyzing the sounds themselves to look at the physics of it to see, if this is what the sound amplitude is, and this is the environment they’re making the sound within, how far can the sound actually generate echoes that would be useful. 

My main research actually focuses on the way that learning changes the brain’s processing of sound. This occurs in pretty much all mammals that have been studied and definitely in humans. And so a lot of my research over the last 20 years has been just seeing how rapidly a brain can modify the way it responds to sounds, how easily it can pick up on very small differences through repeated experiences.

How far can the whale sounds travel underwater?

If you’re talking about humpback whales, their sounds can easily travel 10 kilometers in most contexts where they sing. They can also be detected as far as 100 kilometers away. And if you’re talking about other whales, like a blue whale or a fin whale, their songs have been detected as far as 1,000 kilometers away, which is pretty impressive for an animal. 

What happens with echolocation is that when it hits an object, only part of the sound is reflected back. So if you produce an extremely loud sound, you’re only getting a little bit of that energy back. The loudness of the sound is not to make it go really far, but it’s to make the echoes detectable that aren’t as far.

So what are the whales actually seeing with their sound? 

Based on my analysis of what the sounds are like, they’re primarily focused on large targets that would be moving. I think what they really care about is what other whales are doing. Unlike dolphins, they don’t spend their lives with specific individuals, they’re kind of all nomads. They’re all on their own. And they’re not always in the same spot. They’re migrating from Antarctica or Alaska to some tropical island and back every single year. And they may not see the same whale twice in their lifetime.

When the whales are singing, they’re by themselves, and almost always they’re not moving. So they’re just kind of hanging there in the water. But then when they actually swim off, they stop singing and usually swim off in a very directed manner. So it’s clear that when they start swimming, they’ve decided, the singing time is over and I have to go be in some position based on whatever they’ve learned.

So I think for them it’s a matter of keeping track of, here’s what’s happening around me. It’s a kind of exploratory social scenario where the only way they can really monitor what other animals are doing that are located, you know, 10 kilometres away is to scan really broad sections of ocean and keep monitoring when new whales show up and when they leave.