Animals did not respond to whistles that were not their own signature. This study provides compelling evidence that a dolphin’s learned identity signal is used as a label

The whistles are signature high-pitched sounds that are created by individual dolphins as they grow which they then use throughout their lives to broadcast their locations to other dolphins they meet at sea.

Dolphins make a lot of vocalisations to communicate with each other, including echolocation clicks, whistles to attract other animals to food locations and other noises to indicate how aggressive or friendly they feel. The signature whistles are most often used by dolphins when they are travelling in groups and want to let their companions know where they are.

The team, led by Stephanie King of the university's Sea Mammal Research Unit, monitored the movements and communications of nearly 200 dolphins in the North Sea off the coast of Scotland. His research team wanted to know how far dolphins were using these skills to identify each other and themselves.

While tracking 12 distinct groups of the mammals, the team recorded every acoustic click and whistle using hydrophones, before identifying "signature whistles" using their SIGID technique, which is based on dolphins' acoustic "stereotypy and temporal patterning".'

The results, published in the Proceedings of the National Academy of Sciences, showed that dolphins responded to their own signature whistles whenever they heard them by whistling their own "name" back, but would ignore the whistles of others.