Dolphins ‘shout’ to offset man-made background noise | dolphins

We’ve all experienced the frustration of trying to strike up a conversation in a noisy bar or restaurant. Researchers have now shown that dolphins may experience a similar scenario, which shows that they “shout” to each other when faced with background noise.

The results revealed that a noisy environment makes it difficult for dolphins to communicate and collaborate on tasks, which increases concern about the impact of human noise pollution on marine life.

“In a very loud pub, we find ourselves increasing our voice volume,” said Pernille Sorensen, a postgraduate student at the University of Bristol and first author of the research, which was published in the journal Current Biology. “The dolphins respond in a similar way – they’re trying to compensate but there’s some communication glitch.”

Dolphins are social and intelligent animals, relying on clicks and whistles to communicate and using echolocation to hunt and navigate. So noise from human activities such as drilling and shipping has a potentially harmful impact on the health of marine communities.

The latest study involved a pair of dolphins, Delta and Rhea, and looked at how their ability to cooperate was affected by background noise. The dolphins were required to work together to press an underwater button on both ends of a lagoon within 1 second of each other—a task some humans find difficult to coordinate. They were released from the starting point during each trial, and in some trials, one of the dolphins was held for five to 10 seconds. This means that the dolphins had to rely solely on vocal communication to coordinate button presses.

When the increased noise levels were played from an underwater speaker, both dolphins compensated by changing the volume and length of their calls to coordinate the push of a button. However, they were unable to fully compensate. From the lowest noise levels to the highest, the success rate for dolphins dropped from 85% to 62.5%, according to the research.

The dolphins also changed their body language, reorienting themselves to face each other more frequently at higher noise levels and swimming across the lake to be closer to each other.

The highest noise levels were comparable to what sometimes occurs in marine environments as a result of shipping and drilling.

“Despite their attempts to compensate, despite their high motivation and the fact that they know this collaborative task well, the noise still gets in the way of their ability to coordinate successfully,” Sorensen said.

Sound travels through water 4.5 times faster than through air, which means that many marine organisms have evolved to rely on sounds to provide important signals for locomotion, foraging, avoiding predators, and enabling communication. Invertebrates and fish hear sounds at a low frequency, while cetaceans (dolphins and whales) can hear very high frequencies of up to 200 Hz and also use active sonar to detect objects, including prey. Humpback whales, singing at a low frequency, can be heard 16,000 kilometers away.

But over recent decades, the underwater sound landscape has changed radically from one characterized mostly by natural sounds to one in which some areas are dominated by human noise pollution, from shipping traffic, seismic exploration, oil drilling, and offshore wind farms. An increase in background noise has been linked to stringing, decompression sickness, and behavioral changes.

“The same reasons that sound is so beneficial for animals to use also make them vulnerable to disturbance from noise in the environment,” Sorensen said.

In September 2020, Australia witnessed the largest whale stranding ever recorded A total of 450 pilot whales were found washed up on the west coast of Tasmania, most of which had to be euthanized due to their poor chances of survival. Some have linked mass delinquency to underwater noise pollution.

Another recent study found that when the rumen They are exposed to seismic air cannons, used for surveying in the oil and gas industry, and immediately begin diving to escape the noise. Scientists said that these high-intensity dives consume much more energy than usual and put the health of marine mammals at risk.

Sørensen said there have been some positive attempts to tackle the problem, such as using bubble structures around construction sites to muffle sounds. Some noise, such as ship engines, is difficult to avoid, but the overall impact can be mitigated by better understanding and taking this into account how noise affects marine life. “Maybe there are times of the year when it’s better not to be in a certain area,” Sorensen said. “So you can reduce traffic at certain times and increase it at other times.”

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