Many marine mammals, although unable to speak, rely on communication using sound signals for joint hunting and other activities that require harmony, for which they have evolved their own highly complex language.
However, in recent years, ocean noise pollution due to human activities has increased dramatically and is already harmful to some animals.
Scientists have discovered that noise from ships and oil rigs causes decompression sickness in whales, changes their behavior and disorients them, often stranding them on shore.
Dolphins have even turned out to sometimes yell at each other, which can negatively affect their health and population size, a new study shows.
Dolphins are marine mammals that rely on whistles and echolocation to communicate, form flocks, and reproduce.
But large-scale noise from human activities such as shipping and construction has increased dramatically in recent years.
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"If groups of animals in the wild are less efficient at foraging together, then this will negatively affect the health of the individual, which ultimately affects the health of the entire population," said Stephanie King, co-author of the study and associate professor at the University of Bristol.
Sound is one of the most important senses for marine animals.
Unlike light, which is quickly absorbed by water, sound can travel tens, if not hundreds of kilometers.
As a result, whales, dolphins, porpoises - have developed a complex range and can "talk" to each other.
It is already known that they will be louder to try to overcome noise pollution caused by human activities.
"We knew from previous studies that noise pollution affects animals, but this study also shows how noise affects how animals work together," says Pernille Mair Sorenson, a PhD candidate at the University of Bristol who led the research team.
The study, published in the journal Current Biology, she found that the dolphins' efforts to "shout" over the noise created by humans and their activities were not enough and that they struggled to work together.
In an experimental lagoon with trainers, a study was conducted on two dolphins, Delta and Reese, who were required to perform a joint task by pressing a button.
Each dolphin was fitted with a temporary meter that recorded behavior and sounds.
Scientists found that dolphins who were exposed to higher levels of noise almost doubled the duration of their shrill sounds.
At the same time, Reese and Delta looked at each other much more often, since dolphins have directional hearing, and when they see each other, it is easier for them to discern what their partner "said" in the noise.
Despite their efforts, Delta and Reese were only able to hear each other 62,5 percent of the time when exposed to more noise compared to 85 percent understanding under controlled conditions.
The highest level of noise they were exposed to was 150 decibels.
The sound produced by a huge tanker or a large cargo ship while moving through the ocean reaches a volume of up to 200 decibels, according to the Natural History Museum.
"If you're exposed to noise and it prevents you from communicating with your friends when you're foraging together, it can lead to missed opportunities and can have an impact on your health, especially if it's a behavior that's essential to your survival," explains Sorenson.
"If you're exposed to it longer and longer, it could have larger consequences at the population level," he adds.
This paper adds to existing research linking noise pollution with negative impacts on marine mammals.
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