Dolphins call each other by names, a unique sound for each one, according to a research team from the University of St. Andrews in Scotland.
The scientists recorded the sounds Bottlenose dolphins made and found that each dolphin is called to with a unique sound that the other dolphin responds with their own sound.
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"Bottlenose dolphins develop their own unique identity signal – the signature whistle," read the study, which was published in the Proceedings of the National Academy of Sciences.
"This whistle encodes individual identity independently of voice features," the study said. "The copying of signature whistles may therefore allow animals to label or address one another."
Researchers have long suspected that the marine mammals use distinct names to call one another, however, this is the first study to show that dolphins have names for one another, the BBC reported.
"(Dolphins) live in this three-dimensional environment, offshore without any kind of landmarks and they need to stay together as a group," Dr. Vincent Janik, from the university's Sea Mammal Research Unit,
told the BBC. "These animals live in an environment where they need a very efficient system to stay in touch."
In the study, the researchers recorded the sounds made by wild Bottlenose dolphins and then played back the specific sounds for each dolphin through underwater speakers.
Upon hearing their distinct sound, the dolphins were found to answer back with their own distinct whistle, according to the study. Researchers concluded that such a response was similar to when humans respond when hearing their own name, only in the case of the dolphins, they did so my mimicking a distinct whistle.
According to the St. Andrews research team behind the study, the whistling skill likely evolved as a means by which to communicate over vast distances underwater, allowing the group of dolphins to maintain group cohesiveness.
"Most of the time they can't see each other," Janik said. "They can't use smell underwater, which is a very important sense in mammals for recognition, and they also don't tend to hang out in one spot, so they don't have nests or burrows that they return to."
Certain species of parrot are also believed to use specific sounds to label one another in a group, the BBC notes.
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