Bottlenose dolphins can use learned vocal labels to address each other
See this link
This piece is in line with all our thoughts that Dolphin whistles and calls are in fact the individual’s name or call sign.
These ‘vocalisations’ are not language, but more like “come in No.9 I want to communicate with you”. We still believe that Dolphins actually communicate telepathically. If you were designing a dolphin that is highly intelligent and can find its food in 15% of its day and has no hands how would you communicate?