Bottlenose dolphins have a strong memory

Dolphins are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: frequency modulated whistles, burst-pulsed sounds and clicks. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to the way human vocal cords function,[56] and through burst-pulsed sounds, though the nature and extent of that ability is not known. The clicks are directional and are for echolocation, often occurring in a short series called a click train. The click rate increases when approaching an object of interest. Dolphin echolocation clicks are amongst the loudest sounds made by marine animals.[57]
Bottlenose dolphins have been found to have signature whistles, a whistle that is unique to a specific individual. These whistles are used in their communication to identify an individual. It can be seen as the dolphin equivalent of a name.[58] The signature whistle of male bottlenose dolphins tends to be similar to that of their mother, while the signature whistle of female bottlenose dolphins tends to be more unique.[59] Bottlenose dolphins have a strong memory when it comes to these signature whistles, being able to relate to a signature whistle of an individual they have not encountered for over twenty years.[60] Research done on signature whistle usage by other dolphin species is relatively limited. The research on other species done so far has yielded varied outcomes and inconclusive results.[