Scientist says we’ve got whale song all wrong

When Eduardo Mercado first heard humpback whales sing, he was captivated by their rhythmic, moaning, haunting sounds.

Mercado is a bioacoustician, a scientist who studies the sounds made by animals, and he was notwere convinced that the songs of humpback whales were mating calls, as many scientists believed at that time.

Instead, he wondered if they could use their songs as sonar, detecting echolocation, as do toothed whales such as dolphins. This set him on a lifelong journey to try to understand what all their singing really meant.

Mercado, a professor in the Department of Psychology at the University at Buffalo, has poured his decades of research into a new book called Why do whales sing?. This is part of his conversation with Quirks and Quarks host Bob McDonald.

What exactly is whale song?

Whale songs are not exactly like the songs of humans or birds because they do not start and stop. If you record very large whales – baleen whales, including humpback whales – if you record them singing, in many cases they will continue to make sounds continuously for several hours. And if you watch what they do, you will realize that they cycle through a fixed sequence of patterns. But there is no clear beginning and end. It's more like an acoustic carousel where they always move in the same order.

In your book, you argue that whales don't actually sing the way we humans think of the term. What do you mean?

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

What In this book I propose, and this is what I have been offering for some time: The thing is, what scientists call songs is actually a complex form of echolocation, similar to what bats do, but on a much larger spatial scale. Thus, whales do not serve other whales, but are actually exploring to create their own internal representation of what is happening around them.

Why do other scientists believe that these songs are actually courtship rituals?

There are many reasons why people are convinced that this is what is happening. I would say the number one reason is that most of the humpback whales that were sexed by singing were male, so there is a sex difference. They often sing in environments where reproduction is occurring, so it definitely has something to do with sexual reproduction. And then, the very complexity of it all makes them think that it must be some kind of spectacle, like the tail of a peacock.

Why didn't this idea resonate with you?

I analyzed sounds in songs. And after analyzing about ten years of songs that were recorded before I started, I noticed that the sounds they used changed over time, from year to year, in such a way that if you made an alphabet of the sounds they used in, say, 1992, that alphabet would no longer be in use in the year 2000.

And this seemed strange to me, because no other mammals did this, and birds certainly did not do this. It's like a peacock's tail that changes every year. And I didn't understand how other whales could judge it unless there was always something consistent about it that made it possible to say: this is the best song you can create.

So what made you believe it could be sonar?

At that time I was studying dolphin echolocation. And I've read some research on beluga whales, which when they use echolocation, usually performs normal dolphin echolocation by making clicks and returning echoes. But if you ask them to echolocate objects that are very far away from them, they will go into a different mode of echolocation – these little bursts of clicks. I thought, “Oh, so if you're going to echolocate things that are very far away, you need to do something different from the norm.”

When whales sing, they are alone and almost always do not move.– Eduardo Mercado

And then I started looking for more evidence of animals that echolocate far away, like bats, and I found that they were doing things very similar to what whales were doing in very similar contexts, and then I started looking to see what the implications of that would be. And I did some experiments looking at the physics of this process, whether a whale could detect, say, another whale two kilometers away with its song, and it worked physically.

How have you studied the sonar capabilities of whales throughout your career?

So I attacked this in several ways. The first was simply to analyze the sounds themselves to look at the physics of them and see that if this is the amplitude of the sound, and this is the environment in which it makes the sound, then at what distance can the sound actually generate an echo that would be useful.

My main research is really focused on how learning changes how the brain processes sound. This occurs in virtually all mammals that have been studied, and especially in humans. And so much of my research over the last 20 years has been to see how quickly the brain can change its response to sounds, how easily it can pick up very small differences in repeated experiences.

How far can whale sounds travel underwater?

If you're talking about humpback whales, their sounds can easily travel 10 kilometers in most cases when they sing. They can also be detected at a distance of up to 100 kilometers. And if you're talking about other whales like the blue whale or the fin whale, their songs have been detected up to 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 make a very loud sound, you only get a small portion of that energy back. The volume of the sound is not intended to make it travel very far, but to make noticeable an echo that is not that far away.

So what do whales actually see with their sound?

Based on my analysis of the sounds, they are primarily focused on large moving targets. I think they really care about what other whales are doing. Unlike dolphins, they do not spend their lives with specific individuals; they are all kind of nomads. They are all on their own. And they are not always in the same place. They migrate from Antarctica or Alaska to some tropical island and back every year. And they may not see the same whale twice in their lives.

When whales sing, they are alone and almost always do not move. So they just hang there in the water. But then when they actually swim away, they stop singing and usually swim away very purposefully. So it's clear that once they start swimming, they've decided that singing time is over and I need to take some kind of stance based on what they've learned.

So I think for them it's a matter of keeping track of what's going on around me. It's sort of an exploratory social scenario where the only way to really track what other animals are doing that are, you know, 10 kilometers away is to scan really large areas of the ocean and keep tracking when new whales come and when they leave.