Signature whistle

A signature whistle is a learned, individually distinctive whistle type in a bottlenose dolphin's (Tursiops truncatus) acoustic repertoire that gives the identity of the whistle owner. The whistles are identified and studied in the wild or in captivity by researchers using hydrophones. Vocal learning strongly influences the development of signature whistles, which can remain stable for up to at least 12 years. More often than not, calves develop signature whistles by the sounds they hear while making sure that they differ from close associates. However, male calves tend to learn signature whistles that resemble their mother's. They are believed to be most frequently used in the communication of captive bottlenose dolphins, along with having specialized functions and properties. Signature whistles are in a higher frequency range than humans can hear. Researchers define a signature whistle as a whistle with a unique frequency curve that dominates in the repertoire of a dolphin. Each dolphin has a distinct signature whistle that other members of its social group use to individually identify the whistler. They are typically used for localisation purposes, however they also provide dolphins with behavioural context. Signature whistles have an important role in facilitating mother–calf contact, group cohesion and social interaction.