You know those cute little whistle sounds that dolphins like to make? Turns out that they're not just trying to make us laugh, but they actually have their developed these signature whistles to introduce themselves when meeting one another.

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Marine biologists from the University of St. Andrews had followed a group of bottlenose dolphins around the eastern coast of Scotland and recorded their sounds. They found that the dolphins used their signature whistles when they met up with another group, but they typically only gave the whistle if they were actually mingling with the other dolphins. And that only one member of each group would give the whistle, which may indicate its "leader of the pack'" status. More from Science:
The group could have a leader doing the "talking;" the dolphins may have identified each other using echolocation (the clicks the dolphins send out that echo back from nearby objects), and the whistle was more of a ritual; or the groups may have been together previously and already known each other.

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The study also sheds some light on dolphin society, says Heidi Harley, a comparative cognitive psychologist at the New College of Florida in Sarasota. "Dolphins live in groups that come together and break up, often ending up composed of different individuals," she says. "Exchanging signature whistles may be one way they manage these interactions."