How did King and Janik discover that dolphins use whistles to identify each other?

Question

A
They compared the recordings of individual dolphin whistles to recordings of birdcalls.

B
They recorded individual dolphin whistles in the wild and studied them in their laboratory.

C
They followed the same dolphin group for years until the individual dolphins trusted humans.

D
They played the recordings of unique whistles to dolphins and listened as individual dolphins responded.

Answer 1

B
They recorded individual dolphin whistles in the wild and studied them in their laboratory.