Dolphins need to ‘scream’ to communicate over human-generated sounds, study finds



CNN

One study found that Dolphins are unable to communicate effectively When exposed to sounds produced by humans, it causes them to change their sound like people do when they scream.

An international team of researchers from the University of Bristol, the Dolphin Research Center, Syracuse University, Woods Hole Oceanographic Institution, Aarhus University and the University of St Andrews collaborated on the study. That was published Thursday in Current Biology

“We wanted to investigate how sounds affect animals working together,” said Pernil Sorensen, the paper’s first author and PhD candidate at the University of Bristol, in an interview with CNN. “So basically look at the whole communication network, from a sender to a receiver, and see if there’s any effect on that transmission.”

Previous research Other aquatic mammals such as whales have documented the harmful effects that noise pollution can have. Constant noise from ship engines and military sonar makes it difficult for marine mammals to communicate with each other and has been linked to increasing collisions between whales and ships.

Researchers have shown respect to dolphins because the aquatic animals are highly social and intelligent, using whistles to communicate with each other and echoes and clicks to hunt. And sound communication is especially important for underwater creatures because below the water’s surface, “sound travels very far and very fast,” Sorensen said.

Additionally, dolphins have a “comprehensive vocalization” that they employ “for essentially all aspects of their lives, including coordination of cooperative behavior.”

To understand how noise pollution affects dolphins’ ability to cooperate, scientists worked with two specific dolphins, Delta and Reese, who live at a dolphin research center in Florida. The dolphins had a mission: each of them had to press an underwater button at the same time. Dolphins were asked to perform the task under ambient noise conditions and under four “noise treatments” meant to simulate human-made underwater noise pollution. A total of 200 trials were conducted with dolphin pairs, each dolphin wearing an acoustic tag that recorded its sound production.

The findings were twofold, Sorensen said. First, they found that dolphins use “compensatory mechanisms” to compensate for their impaired vocal communication. As the underwater noise increases, they make louder and longer sounds and change their body language to face each other.

But the more important finding, according to Sorensen, is that despite using their effort to compensate for the noise pollution, the dolphins were still less successful at completing the task. Their success rate dropped from 85% to 62.5% from the lowest to the highest level of noise.

“We show for the first time to our knowledge that animals working together are affected and that compensatory mechanisms are insufficient to overcome the effects of noise,” he explained.

This could have real-world impacts on dolphins in the wild, which depend on cooperation for foraging and reproduction. “They need words to connect,” he said.

Sorensen added that the researchers “would have liked to introduce or include more dolphins in our experiments” and that future experiments could expand the sample size to a larger group of dolphins.

Additionally, more research is needed on the specific types of whistles and sounds that dolphins use for cooperative work.

“This research clearly contributes to our knowledge of how noise pollution affects animals as a piece of the puzzle,” Sorensen said.

He said he hopes the research will help support “solutions for how we can better manage noise in our oceans.”

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