How fiber optic cables helped researchers listen to whales

Scientists ‘spied’ whales in the Arctic using fiber optic cables. In July, a group of scientists published a study that took a practical method usually used to monitor the cables themselves and used it to monitor baleen whale activity in the Arctic. Researchers say similar studies could transform the way scientists collect data on marine life.

Beneath the oceans, fiber optic cables carry internet traffic around the world. They have also become a common tool for field scientists who want to collect and access data in real time. In particular, they can be used to detect earthquakes, including aftershocks that are not detected by traditional seismic stations. In this case, these cables were used to detect whale sounds. This is the first time wildlife monitoring has been done using a technique called distributed acoustic sensing, the study notes.

“[With] distributed acoustic sensing, we can potentially have better coverage,” said Léa Bouffaut, co-author of the study as a student at the Norwegian University of Science and Technology. The edge. “It can open up new possibilities in places that are too complicated to access or in regions where governments are unable to fund new projects like this,” said Bouffaut, now a researcher at K. Lisa. Yang Center for Conservation Bioacoustics at Cornell University.

Fiber optic cables criss-cross large areas of the seabed

Whale researchers like Bouffaut typically use hydrophones to monitor underwater whale activity. Although the hydrophone provides good quality data, it cannot cover as much ground. Hydrophones are typically deployed about 10 to 20 kilometers apart, Bouffaut explained. This relatively close proximity gives scientists a good idea of ​​where the whales might be, a method similar to using cellphone tower triangulation to detect the location of where a phone call has been passed. But the oceans are huge, and even a large array of hydrophones can only observe a small area. Fiber optic cables, on the other hand, criss-cross large areas of the seabed.

Distributed acoustic sensing is already being used to check the condition of undersea cables and can alert communications companies to problems, such as a line break. It works because a fiber in the cable is connected to what’s called an interrogator, a device that measures whether a fiber-optic cable is functional, Bouffaut explains. The interrogator sends light pulses to the fiber optic cable at regular intervals. Sounds or vibrations can disturb the cable and the impulses passing through it. By observing changes in the light reaching the interrogator, researchers can determine what is happening near the cable, whether it is an anchor dropped near a cable or a whale singing nearby.

Here is the sound of whales captured by virtual hydrophones.

Bouffaut calls the result “virtual hydrophones”. During the experiment, the researchers placed these “virtual hydrophones” about four meters apart. The received data can be interpreted audibly, but it can also be visualized.

Similar to how fiber optic cables pick up vibrations from an earthquake, the cable can pick up sounds through seismic vibrations bouncing off the fins of male whales. Yes, flippers. Apparently, the fins of male whales can emit fin whale songs through a “series of repeated short, low-frequency pulses that share similarities with airgun blasts,” according to the study.

More data on baleen whales in particular could help fill major gaps in our understanding of whale species, especially in the warming Arctic where this research took place. Even though they are some of the largest animals on the planet, researchers don’t have enough information about some whale species to know if they are threatened or endangered.

“We need to have scientific evidence of what they do and how they do it”

“We need to have scientific proof of what they do and how they do it,” Bouffaut explained to The edge. Using fiber optic cables, researchers can tell when whales are struck by boats, caught in fishing gear, have migrated in a different direction and, as mentioned above, whether they are present in a specific region. The information collected is also essential for keeping tabs on the whales as they recover and deal with a commercial whaling industry.

Now that the researchers have collected the data for their study, Bouffaut is looking at other uses for the recording technology. Some curiosities Bouffaut wants to keep in mind are whether they can only record at low frequencies, how many different species can be recorded, and how far researchers can record a whale.

“One of my hopes is that we can exploit the idea that because we can receive the data in real time, we can process the data in real time,” Bouffaut said. “I think it’s something that can be useful for the bioacoustics community because there are a lot of conservation issues that need real-time monitoring.”

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