How humpback whales communicate through a hidden global network of song

If you stopped reading this and sang as loud as you could, how far do you think that noise would travel? The answer, if you're a humpback whale: tens of kilometres.

Not only do these extraordinary animals – who can reach 30,000kg in weight – have a phenomenal acoustic range, but they can also sustain their singing over huge periods. While many of their vocalisations can last over 30 minutes, the mammals can repeat these for many hours (the longest known recording of a whale song is a staggering 22 hours).

But what's the purpose of these noises? At the moment, experts have yet to form a complete understanding. However, ground-breaking new research has monitored how songs have spread and evolved throughout the South Pacific, revealing a sprawling age-old acoustic community that may connect whales worldwide – and help them form life-long relationships.

To dive into the biggest questions of whale social vocalisation, we sat down with Dr Michelle Fournet and Dr Ellen Garland, whose revolutionary research on humpback communication takes centre stage in the new Apple TV documentary Fathom (now available to watch).

Why do whales sing?

All humpback whales – males and females, can make social calls from a young age. Even neonate whales – those less than a month old – have been known to make vocalisations recognisable to the human ear. However, it’s only the males that truly sing.

“We don't know the exact function of the songs at this point. But it could be part of male-male competition, or to attract a mate. Or they could be a multi-message signal,” says Garland.

As she explains, the songs themselves are incredibly complex. Made up of a number of noises that form ‘phrases’, these are repeated again and again to create what’s known as ‘themes'.

Incredibly, these phrases and themes can change as whales from different parts of the world socialise, creating an acoustic network.

There's another layer of complexity to this web of noise. As Garland explains in Fathom: "Underwater, sounds can take half an hour to bend around the horizon. Or they can fade in a matter of seconds. Sounds constantly arrive from different spaces and times. And somehow whales decipher an acoustic world where the past and present arrive all at once. It’s like knowing how each of the stars fit within time using just your ears."

She adds: “The song itself is continually evolving, continually changing through time – being passed from one population to the next. And all males are incorporating these changes into their own song as populations come into contact with each other.

“Our best analogy at the moment is human fashion, where a new look comes about and everyone switches. Or a new pop song comes available and everyone is suddenly listening to it.

“We’ve tracked multiple song revolutions spreading across the South Pacific Ocean basin, showing how this incredible widespread cultural change happens really rapidly. This is really not normal in the animal kingdom.”

Read more about whales:

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• How does human noise affect ocean life?

But while not all humpbacks sing, most will make more general smaller growling noises to make contact with nearby whales.

“A whale that makes no sound is functionally not there to the other animals. If a humpback wants to know if other animals are around, they have to produce a sound. The whales in Alaska can’t see more than 10 metres from themselves. But they can communicate for four kilometres,” explains Fournet.

“It isn't necessarily because they want to get together. And in fact, what we find is they call back. They don't join. They're just calling back and forth as if to say ‘I am here and there you are.’”

“Whales are social on a scale that is difficult for the human eye to perceive. Whales in southeast Alaska will maintain relationships for decade. They'll get together every year in similar locations to forage together."

How can whales actually sing?

As with many facets of whale song, the biological mechanisms humpbacks use to produce their vocalisations aren’t completely understood.

“You can't do an X-ray on a humpback whale or an MRI – we can’t keep them in captivity. So for us to understand something that's going on inside a large whale, we need to look at a recently deceased body (a whale that's died naturally).

“It literally requires people to go on beaches with chainsaws and hacksaws and go inside an animal's body and try and do this before the vocal apparatus has actually decomposed, which is very, very quickly.”

However, despite these restrictions, scientists have developed a theoretical understanding of how whale noises are formed.

“To the best of our knowledge, whales make sound by moving air between various sinus cavities in their skull and across something called ‘phonic lips’ or ‘vocal folds’. In this way, it’s not that different from us,” says Fournet.

“One of the big differences between us and whales is that when we produce sound, air expels from our mouth – we are inhaling and exhaling as we do so. Whereas when whales vocalise, they're doing so underwater in a closed system – they’re moving air around internally.”

Will we ever be able to talk to whales?

It’s tempting to think that as our understanding of whale vocalisations develop, humans may someday be able to communicate with whales.

After all, while investigating humpback calling behaviour in the field, Fournet has been able to replicate a short ‘conversation’ with whales. Using an underwater playback machine to transmit greeting calls, she has received signals back from other humpbacks.

However, she maintains that such experiments are only undertaken to better understand whales – and find out how human activity (such as shipping) could impact them.

“My goal as a researcher is not to talk to whales. My goal as a researcher is to find out how whales talk to each other. And that is a big and extremely important difference,” she says.

“I think that it is borderline unethical for us to try and talk to whales. The only reason that we have to alter the behaviour of a whale is to find out something that's really critically important.

“If we're going to protect this animal from anthropogenic noise and changes in the soundscape, we have to understand what these calls are for.”