Two marine biologists studying dolphins have found that when a new group of dolphins meets another they have a signature whistle they use as a greeting.
Sort of like a: "Hello, I am Delphino, of the clan Swimsalot."
And then the other group responds with their whistle like: "What's up, yo."
It's just one dolphin that does the whistle, like their leader.
The whistle was only used if they were specially interacting with another group of dolphins, not just near by others.
So this really is a "hello!"
A Cetacean biologist who read the study said this could open up all sorts of possibilities.
"We know dolphins learn to copy each other's signature whistles. What if they use a signature whistle to refer to a 'third party' or a dolphin that isn't there?"
Dolphins can talk smack on each other!
They're just like humans!