Vocalization of naive captive dolphins in small groups.

Pure-tone whistles (2403) by four individual dolphins (Delphinus delphis bairdi) were analyzed for duration and the elapse of time before either response by another animal or a repeat whistle by the same animal. Only five major types of whistle emissions were recorded, all stereotyped and each characteristic of the animal emitting it. Only one of the four animals emitted two different whistles, one of which was rare and both of which were stereotyped. A pure-tone chirp and pulsed sounds are discussed. We found no evidence of a dolphin "language," but we present evidence of social response to acoustic signals.