Walrus knocking, seals trilling: These are the sounds of the Arctic

Originally published on February 29, 2020.

For the past four years, scientists have been listening in on the animals moving through the northern Bering Sea, between Alaska and Russia.

This area is a busy migration route for hundreds of thousands of whales, walruses, and ice seals, but little is known about how the animals use the area, and how that is changing as the climate warms.

"The Arctic is experiencing rapid and tremendous changes and yet there was very little information in this region," said Howard Rosenbaum, director of Wildlife Conservation Society's Ocean Giants Program. "How are these animals using this particular habitat? What does that soundscape sound like? How do animals communicate in this space? When are they present?"

To answer these questions, Rosenbaum and his colleagues installed audio recorders — anchored to the seafloor with weights — to capture the year-round soundscape of not only the animals in the region, but also the human-caused noises, such as those from ships.

"This is a classically quiet environment and we know it's getting noisier as there's less ice," said Martin Robards, the director of Wildlife Conservation Society's Arctic Beringia Program.

"You can liken it to walking down a street in a busy city, maybe New York or Ottawa, where you're talking to somebody and then the traffic picks up and suddenly you're having to speak really loudly for them to hear you," he said.

"Marine mammals face the same issue in the water as that environment gets noisier. They have to communicate more loudly or maybe not being able to communicate across such large distances."

'I wonder if I'll ever see that again'

Working with local Indigenous fishermen and hunters, they set out to deploy recorders in three separate locations around St. Lawrence Island. Their first attempts were delayed because of the Arctic's notoriously turbulent weather.

"We were all set to go out and deploy that first recorder, and the weather came in and we had eight- to 10-foot swells for the next week. We weren't able to do anything. We were just waiting, waiting, waiting to go out in the boats," said Robards.

Once they deployed the recorders, they had to wait until the next year to know whether they had actually captured anything at all.

"You put it over the side and watch it disappear into the depths, and a part of you is definitely thinking, 'I wonder if I'll ever see that again,'" said Robards.

"Then it's a waiting game in essence," said Rosenbaum. "Now we've just got to hope for the best."

The team was able to recover most of the recorders, although "there's also a few of those still on the bottom of the Bering Sea," said Robards. "We tried pretty hard to find them but they're still down there."

After recovering the recorders, a team went to work analyzing thousands of hours of recordings, using computer algorithms to search for recognizable animal calls. 

"We actually ended up with 33,000 plus recordings of Arctic marine mammals from this dataset," said Rosenbaum. A paper looking at the anthropogenic noises captured is still in the works.

'Cool science' to help protect marine mammals

These recordings will help paint a picture of the animal life in this area so that, in the future, scientists can monitor how these populations shift as the Arctic warms, and as more ships move through the area.

"And as this environment rapidly changes, it actually empowers us and our colleagues and our partners from Indigenous communities to use this information to better protect these animals ... from the impacts of noise and the changing environment," said Rosenbaum.

"It's cool science. It's engaging and it also can help establish a connection to these animals with people that will never ever get a chance to see them."

The results were recently published in the journal Marine Mammal Science with contributions from the Wildlife Conservation Society, Columbia University, Southall Environmental Associates, and the University of Washington.

Produced and written by Amanda Buckiewicz

Shipping sounds courtesy of Thomas R. Kieckhefer and Peter M. Scheifele/DOSITS