A COMPARATIVE STUDY OF THE PURE TONAL WHISTLE VOCALIZATIONS FROM FIVE WESTERN NORTH ATLANTIC DOLPHIN SPECIES

Pure tonal vocalizations, or "whistles", from five species of dolphins native to the western North Atlantic were examined and compared. The five species of dolphins were Tursiops truncatus, Lagenorhynchus acutus, Stenella plagiodon, Stenella longirostris, and Globicephala melaena.; Recordings made from 1964-1977 in locations ranging from Nova Scotia to the Caribbean were scrutinized for the presence of whistle vocalizations and all such whistles with suitable signal/noise levels were selected and re-recorded. Whistles were spectrographically analyzed and printed on lithographic paper. Each whistle was then individually measured and quantified using a minicomputer and graphic board. Six parameters were measured: beginning frequency, ending frequency, maximum frequency, minimum frequency, total duration in seconds, and number of inflection points. Comparisons within and between species were made with the use of discriminant analysis.; The generalized pattern for each species' whistle repertoire was described using parameter means and coefficients of variation (C.V.). All five species exhibited a consistent pattern in the relative values for C.V. Maximum frequency had the lowest C.V. for all five species, while duration and number of inflection points had the highest C.V. for all five species. Recording samples from all species contained rhythmic repetitions of identical whistles. These repeated whistles may be a form of signature whistles.; Comparisons within and between species' whistle patterns indicated significant species-specific differences. T. truncatus and G. melaena whistles were both highly distinctive from other species and from one another. The whistles of L. acutus, S. plagiodon, and S. longirostris were less distinctive, but still different enough to be discriminable. The relative degrees of species distinctiveness were broadly correlated with taxonomic and zoogeographic relations. Differences among sympatric species were greater then differences among allopatric species.