‘Shazam for whales’ uses AI to track sounds heard in Mariana Trench

A mysterious sound emitted from the deepest part of the ocean has finally been identified as a Bryde’s whale. Now, artificial intelligence is helping researchers track the elusive whale species responsible for the call.

The puzzle began in 2014 when researchers recorded a sound resembling a moan followed by metallic sweeping pings over the Pacific Ocean’s Mariana Trench. “Your average person would not think that it was made by an animal – they would think it was some ship or the Navy,” says Ann Allen at the National Oceanic and Atmospheric Administration (NOAA).

Years later, additional recordings of the sound, which researchers call a biotwang, were eventually linked to sightings of Bryde’s whales (Balaenoptera brydei) near the Mariana Islands.

Bryde’s whales are large baleen whales that filter huge amounts of krill and fish from the water, but they are rarely seen because they are nearly always on the move. Allen saw an opportunity to track migrating Bryde’s whales by finding similar biotwang sounds in more than 180,000 hours of underwater recordings from NOAA’s network of hydrophones mounted on the Pacific seafloor.

“It’s important any time you can discover a new call type for any species of animal that occurs most of the time out of sight of people because it allows you to use passive acoustic monitoring to detect their presence,” says Caroline Casey at the University of California, Santa Cruz.

Given the impracticality of manually sifting through the audio recordings, Allen teamed up with Google researchers who had been developing an AI model to automatically identify vocalisations of multiple whale species. Google trained its AI to categorise different patterns in spectrogram images, which convert sound to a visual form.

The AI was able to identify calls – a bit like the music-identifying app Shazam – by comparing them to the training set. It was successful at identifying calls from eight species: humpback whales, blue whales, fin whales, North Pacific right whales, North Atlantic right whales, minke whales, killer whales and Bryde’s whales – you can hear one below.

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