The research sheds new light on the intelligence of dolphins.
Scientists have found further evidence that dolphins call each other by "name".
Research has revealed that the marine mammals use a unique whistle to identify each other.
A team from the University of St Andrews in Scotland found that when the animals hear their own call played back to them, they respond.
Dr Vincent Janik, from the university's Sea Mammal Research Unit, said: "(Dolphins) live in this three-dimensional environment, offshore without any kind of landmarks and they need to stay together as a group.
"These animals live in an environment where they need a very efficient system to stay in touch."
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