AI eavesdrops on dolphins and discovers six unknown click types

A Dolphin Dialogue

An algorithm uncovered six previously unknown types of dolphin clicks in underwater recordings from the Gulf of Mexico, researchers reported in PLOS Computational Biology on Thursday.

Dolphin tracking is normally done using planes or boats, but coauthor of the study Kaitlin Frasier, an oceanographer at the Scripps Institution of Oceanography says that it is too expensive. A cheaper way is to go through seafloor recordings — which pick up the echolocation clicks that dolphins make to find their way around, search for food, and socialise with others.

By comparing different click types to recordings at the surface — where researchers can see which animals are making the noise — scientists can learn what different species sound like, and use those clicks to map the animals’ movements deep underwater.

However, experts come across difficulties when sorting through the recordings, mainly because the differences between the clicks are very subtle to the human mind.

“When you have analysts manually going through a dataset, then there’s a lot of bias introduced just from the human perception,” says Simone Baumann-Pickering, a biologist at the Scripps Institution of Oceanography who was not involved in the study. “Person A may see things differently than person B.” So far, scientists have only determined the distinct sounds of a few species.

A wave-like illustration of the acoustic signals of 52 million dolphin clicks (Credit: K. Frasier)

Frasier and her colleagues outsourced the job to a computer to sift through the clicks more efficiently and precisely. They fed an algorithm 52 million clicks that had been recorded over two years by near-seafloor sound sensors across the Gulf of Mexico. The algorithm grouped clicks based on their similarities in speed and pitch — the same criteria human experts use to classify clicks.

“We don’t tell it how many click types to find,” Frasier said. “We just kind of say, ‘What’s in here?’” The algorithm picked out seven major types of clicks, which the researchers think are produced by different species of dolphin. Frasier’s team were able to recognise the clicks of one species called Risso’s dolphin, and believed another group of clicks to belong to the short-finned pilot whales that frequent the Green Canyon south of Louisiana. Another type resembles sounds from the eastern Pacific Ocean that a dolphin called the ‘false killer whale’ makes.

In order to confirm their suspicions and findings, the biologists need to compare their computer-generated categories against surface observations of these dolphins, Frasier said.

“It would be great to be able to confidently assign certain species to each of the different click types, even if more than one species is assigned to a single click type,” said Lynne Hodge, a marine biologist at Duke University who wasn’t involved in the study. More effectively monitoring dolphins could provide new insight into how these animals respond to environmental problems such as oil spills and the long-term effects of anthropogenic climate change.

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Posted by Hasan MZI

Hasan is a medical student at University College London. He's an aspiring surgeon who loves Arsenal, and he skips leg day at the gym. No abuse please, his mum is protective.

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