Dolphins tend to shout at each other when they work together with loud human-made noise underwater.
Dolphins Recorded Shouting at Each Other
Dolphins are famously intelligent like humans. They are also very cooperative, but human-made noise reportedly affects the way they communicate with each other. They tend to shout at each other to compensate for the noise.
A study led by the University of Bristol experts published in the journal Current Biology revealed that noise from human activity like drilling and shipping drowns out dolphin noise and negatively impacts their health.
Human-made noise directly affects the success of animals working together, according to Stephanie King at the University of Bristol, Mail Online reported. She added that if the noise makes the groups of wild animals less efficient at performing cooperative actions like cooperative foraging, it could significantly impact their individual health and the population's health.
Dolphins make two kinds of sounds - whistles and clicks.
Clicks are used for echolocation, a technique that animals use to determine the location of objects such as food, obstacles or potential dangers using reflected sound waves. Whistles are used to communicate with other members of the species and possibly other species.
Dolphins in human care can work together to solve a cooperative task and understand each role they play in the task. They whistle to coordinate behavior.
How Anthropogenic Noise From Human Activity Affects Dolphins' Abilities
The researchers studied anthropogenic noise sources like drilling, airplanes, motorboats, traffic and more. The experiments were conducted at the Dolphin Research Center (DRC) in Grassy Key, Florida, with two adult male bottlenose dolphins, Delta and Reese, while they were swimming in their lagoon.
The dolphins had been trained to engage in cooperative behavior using the rewards of fish and social interaction. Delta and Reese were equipped with suction-cup tags that recorded their vocalizations as they participated in a cooperative task.
The task required the two dolphins to work together to both press their own underwater button within one second of each other while exposed to increasingly louder levels of noise from an underwater speaker.
To make the task even more challenging, one of the dolphins was held back while the other was released immediately. A variety of noises was used, including the sound of a pressure washer. The noise the dolphins experienced was similar in loudness to noise pollution experienced by animals in the wild.
The dolphins produced louder and longer whistles to compensate for the increasing noise levels. Their struggles in communication were noticeable as they changed the volume and length of their calls to compensate for the increasing levels of noise.
Aside from changing the volume and duration of their noises, their body language also changed.
They tend to re-orient themselves and face each other. They were also more likely to swim to the other side of the lagoon to be closer. Their echolocation decreased as the noise increased.
Dolphins Are Less Successful in Cooperative Tasks With Human-Generated Noise
The study provided a glimpse of what dolphins do to cooperate. However, it also shows that they are less successful as the noise gets louder.
Their success rate dropped from 85 percent to 62.5 percent.
Sørensen said they were aware for years that animals could make attempts to compensate for increased noise in their environment by adjusting their vocal behavior.
The study also showed that their adjustments are not necessarily sufficient to overcome the negative impacts of noise on communication between animals working together.
Sørensen told Mail Online that the noise used in the experiment were not agonizing to the dolphins. He also added that Delta and Reese were not forced to participate in the experiment and had the choice not to do so.
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