Don: Hello, Yaël.

 

Yaël: Don? Where are you?

 

D: I'm behind this door. How did you know it was me?

 

Y: I recognized your voice, of course.

 

D: Did you know dolphins can recognize each other in a similar way? Only instead of   using voices, they use whistles.

 

Y: Whistles?

 

D: Dolphins are social mammals that have evolved to live in an aquatic environment. Like bats, they can use sonar to locate prey by emitting different frequencies of broadband sounds called clicks. But it wasn't until the 1990s that scientists  discovered that they have another kind of sound that they use for communication. That sound is a pure narrowband tone that's frequency is modulated up and down. We call it a whistle.

 

Y: Why do they need whistles?

 

D: Dolphins live in groups, usually mothers with calves or adult males with each other.   Individuals in these groups help each other with hunting, scouting for food sources or protecting each other. Since ocean water is difficult to see through, they have  adopted whistles as a way to keep in touch with each other. But these whistles are not just a way to greet each other. Each individual dolphin has its own signature  whistle, like I have a voice that identifies me. When individuals get separated from each other, they will whistle to let other dolphins know not only where they are, but   who they are.

 

Y: That's amazing, Don.

 

D: Well, dolphins are amazing animals. Like humans, they have large brains for their body size. We are just starting to understand how intelligent they really are.