Dolphins can scream underwater – 01/16/2023 – Science

Mammals swim in the ocean with a healthy world. But in recent decades, humans have been upping the scale, and they’ve been blowing up the water Ship noiseAnd oil and gas exploration and military operations. New research suggests that this human noise can make communication and teamwork more difficult. dolphins.

When dolphins teamed up on a task in a noisy environment, they weren’t all that different from city dwellers trying to be heard by the noise of jackhammers and ambulance sirens.

They screamed, and they screamed louder and louder, researchers reported Thursday (12) an.m Current Journal biology. “However, there is a significant increase in the frequency of coordination failures with them,” said Shane Jirou, a cetacean biologist at Carleton University in Ottawa, Ontario (Canada), who was not involved in the work. The effect of the increased noise was “remarkably evident”.

The scientists worked with a pair of male dolphins named Delta and Rhys in an experimental lagoon at the Dolphin Research Center in the Florida Keys, Florida. The pair was trained to swim to different places in their enclosure and press a button within a second of each other.

“They were always the most motivated of animals. They were really excited about this task,” said Pernelle Sorensen, a biologist and doctoral student at the University of Bristol in England. You are Dolphins talk to each other using whistles She said they often beep right before pressing a button.

Sorensen’s team channeled the sounds using underwater loudspeakers. Tags installed behind the animals’ vents capture what the dolphins hear and “say” to each other, as well as their movements.

Through 200 experiments with five different acoustic environments, the team observed that dolphins altered their behavior to compensate for loud noises. The whales turned their bodies towards each other and paid more attention to their location. Sometimes, they nearly doubled the duration of their calls and amplified their whistles, i.e. screams to be heard over background noise or a pressure washer recording.

And the noisier it gets, the less successful the dolphins will perform. In the highest condition, they were successful 62.5% of the time, pressing their buttons at the same time at 20% lower ambient sound levels.

“It was amazing to see how low the success rate was,” Sorensen said.

In the past, researchers have noticed that wild dolphins change their behavior when boats are around them. For example, in Australian waters, scientists have observed fewer dolphins as more dolphin-watching tour boats increase. But no one has yet investigated how human voices can disrupt the animals’ ability to cooperate.

“Usually it’s very difficult to do these kinds of studies in the wild,” said Mauricio Cantor, a behavioral ecologist at Oregon State University in Newport, who was not part of the study. But he said the experimental setup Sorensen’s team used provided “clear evidence of a noise effect,” because the researchers were able to control for almost anything that might contradict their findings.

Dolphins hunt together, using sound to communicate and finding their way through echolocation. They also use sound to communicate with their families and whistle to indicate they are in pairs, Gero said. In noisy environments, “animals can’t talk to each other.” In the long term, these conditions can affect eating and the ability to conceive, Kantor said.

There may already be parts of Oceans that are no longer usable for these animalsJiro said. Dolphins can migrate from places where they cannot communicate successfully. He said this phenomenon may already be happening in large ports in places like Los Angeles or Boston.

Gero said ships are the main driver of noisy ocean scenes, and in some locations, ships are being slowed down to protect marine life from noise pollution. For example, along parts of the Pacific coast, from Washington state to Chile, boats are instructed to reduce speed or change course to reduce noise that can disturb marine mammals.

“We’re really affecting animals in this way,” Gero said. “The sad truth is, in some ways, this story is 35 to 50 years late.”