Scientists have discovered that dolphins have names – not Flipper, Opo, Ecco or Moko, but "signature whistles" they use to identify one another.
They've long known that dolphins of the same pod use the same calls, but it's the first time it has been shown that each individual dolphin has a unique whistle, which effectively functions as its name.
Researchers at the University of St Andrews in Scotland spent four months recording dolphins from different pods whistling, and played them back using underwater speakers, stripping out tonal characteristics that would identify the dolphin giving the original whistle.
"We played signature whistles of animals in the group; we also played other whistles in their repertoire and then signature whistles of different populations - animals they had never seen in their lives," says Dr Vincent Janik of the university's Sea Mammal Research Unit.
What they found was the dolphins only responded when they heard their own signature whistle, by whistling back. Some of the dolphins then approached the boat carrying the speakers, as if they had been called over.
If the whistle was of a dolphin from a different pod, they ignored it.
No two whistles are alike, but it's not yet known how the dolphins get their "names", according to marine biologist Laela Sayigh. They might produce them spontaneously, or piece together bits of whistles they hear when they're young.
"We don't really have an exact answer," she told the Los Angeles Times.
Ms Sayigh says they're no sure whether dolphins are able to talk about other dolphins or use whistles to refer to other creatures or abstract concepts, like humans.
"I think there's a strong likelihood they can, but we've still got a lot more to explore."
It's believed this is the first time animals have been documented using names in the wild. The study was published earlier this week in the Proceedings of the National Academy of Sciences.