Bottlenose dolphins develop their own unique signature whistle early in life, creating a sound that identifies them as an individual. They use these whistles to announce who they are and stay connected with their group, particularly when separated or unable to see one another. Even more fascinatingly, dolphins can imitate another dolphin’s signature whistle to address that specific individual. When researchers played recordings back, dolphins responded most strongly to their own whistle—much like hearing someone call your name across a crowded room. Apparently dolphins had personalised contact lists long before we invented phones.