Whales learn their whimsical songs from one another and thanks to fibre optics we can eavesdrop as never before

Whales emit some of the most recognisable noises in the animal kingdom and their haunting songs have become a listening staple of many a recording recommended by relaxation therapists.

Two new pieces of research published this week have shed light on their singing, but in very different ways.

A University of Queensland-led study published in Scientific Reports has found that humpback whales (Megaptera novaeangliae) can learn extraordinarily complex songs from other whales in other regions. In fact, New Caledonian humpback whales can learn songs with remarkable accuracy from their extended family from Australia’s east coast.

“This really indicates a level of ‘cultural transmission’ beyond any observed non-human species,” says lead author Dr Jenny Allen, an honorary research fellow in the School of Veterinary Science at UQ, Australia.

Separately, a new approach to more effectively track whales in their expansive environments, using the web of optical-fibre telecommunication cables along the ocean floor, has been reported in Frontiers in Marine Science.

“I think this can change the field of marine bioacoustics,” says first author Dr Léa Bouffaut, now a researcher at the K. Lisa Yang Center for Conservation Bioacoustics at Cornell University, US. Bouffaut was a postdoc at the Norwegian University of Science and Technology for the research.

The cultural transmission of whale songs

Humpback whalesong audio. Credit: Allen et al.

Humpback whale songs are long, complex vocal behaviour which are only produced by the males. They are made up of individual sounds called “units” that are arranged into a sequence or “phrase”. The phrases are repeated many times to create a “theme”, which are then sung in a consistent order (without repetition) to create what scientists refer to as a song.

Scientists studied the song patterns of male humpback whales from New Caledonia and eastern Australia between 2009 and 2015 in an effort to work out how these songs are culturally transmitted between populations in different regions.

“By listening to the Australian humpback population, we were able to see if the songs changed in any way when sung by the New Caledonian whales,” explains Allen. “We found they actually learned the exact sounds, without simplifying or leaving anything out.

“And each year we observed them they sang a different song, so it means humpback whales can learn an entire song pattern from another population very quickly, even if it’s complex or difficult.”

These findings support the hypothesis that the songs are learned by humpback whales on shared migration routes – like the New Zealand migration corridor – or on shared feeding grounds in Antarctica.

And it’s more evidence that culture isn’t a uniquely human trait and is shared by other animals too.

“It’s rare for this degree of cultural exchange to be documented on such a large scale in a non-human species,” Allen concludes. “We hope these findings provide a model for further study into understanding the evolution of cultural communication in animals and humans.”

Humpback whalesong spectogram
Humpback whalesong spectogram. Credit: Allen et al.

Eavesdropping on whales with fibre optic cables

This audio is series of non-stereotyped arched sounds and down-sweeps, likely from a North Atlantic blue whale. Recorded using Distributed Acoustic Sensing (DAS). Credit: Léa Bouffaut et al.

Currently, researchers use tools like satellite tracking, aerial surveys, sightings, and listening for whale vocalisations by dropping individual underwater microphones (hydrophones) – as were used in the humpback study – to track whales.

But for the first time, researchers have now been able to passively listen to whales using the existing underwater fibre optic cables (used for internet, television, and telephones) that crisscross the ocean floor.

The technique is called Distributed Acoustic Sensing (DAS). It uses an instrument called an interrogator to tap into a fibre optic system and turns unused fibres into a long array of hydrophones that detect movement and noise along the sea floor.

The research was conducted over along the length of a 120km long cable in an area called Isfjorden, in the Svalbard archipelago of Norway, where baleen whales are known to forage during the summer. Over 40 days researchers detected at least 830 whale vocalisations.

“With this system, which is what we can basically call a hydrophone array, we have the chance to cover a much bigger area for monitoring,” says Bouffaut.

“And because we receive the sound at multiple angles, we can even say where the animal was — the position of the animal. And that’s a huge advantage.”

Schematic of how distributed acoustic sensing works
This schematic shows how the Distributed Acoustic Sensing, called DAS, works. A laser pulse is sent from the shore station through a fibre optic cable by an interrogator (a). The fibre has evenly spaced nodes on it, called defects (b). Underwater sounds cause the defects in the fibre to be slightly displaced, which delays the backscatter a signal back to the interrogator, which then interprets the time delay as a strain on the fibre. That in turn can be interpreted as acoustic data. Credit: Marte Finsmyr/Léa Bouffaut

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