Abstract: Humpback whales (Megaptera novaeangliae) produce cyclical, underwater sound sequences that are composed of a variety of structured sound patterns. These sequences have been described as songs and generally are assumed to serve a communicative function. Past studies of the sound patterns and individual sounds within songs often have described them as functionally homogeneous elements varied to convey information about the vocalizing whale. An alternative possibility is that different sounds and sound patterns within songs are functionally heterogeneous elements, some of which could vary for reasons unrelated to information content. To assess this possibility, we analyzed humpback whale songs recorded in Hawaii from 1992-1995 to determine whether whales consistently used some sound patterns more extensively than others, and to measure the stability of the acoustic features of sound patterns. We found that some 'dominant' sound patterns were consistently repeated for substantially longer periods and that other patterns were consistently repeated for shorter periods. We also found that spectral, temporal, and energetic features of sounds within dominant sound patterns were highly stereotyped. Comparisons of the sound patterns analyzed in this study with those described in past studies suggest that some sound patterns within humpback whale songs recur across years and populations. Our findings indicate that the detectability of different sounds and sound patterns within songs varies substantially. We speculate that differences in detectability reflect differences in functionality.
Key Words: CETACEAN; COMMUNICATION; ECHOLOCATION; MYSTICETE; BIOACOUSTICS; MEGAPTERA; SONG
Document Type: Research article