Understanding the structure of humpback whale songs (L).

Structured sound sequences produced by humpback whales are described in the literature as hierarchically organized songs. Despite the prevalence of such descriptions, there is no direct evidence that humpback songs are hierarchically structured. It is suggested here that songs may instead be heterarchically structured, in which case traditional approaches to analyzing songs may obscure their organizational and acoustical features. An alternative framework for characterizing patterns within songs is presented, derived from models of humpback whale sound production, that characterizes rhythmic and sequential regularities in the sound sequences produced by singing whales in terms of interacting cycles of breathing and internal air recirculation.

Rhythmic structure in humpback whale (Megaptera novaeangliae) songs: preliminary implications for song production and perception.

The hierarchical organization of the male humpback whale song has been well documented. However, it is unknown how singers keep these intricate songs intact over multiple repetitions or how they learn variations that occur sequentially during each mating season. Rather than focus on the sequence of sounds within a song, results presented here demonstrate that the individual sounds are organized into rhythmic groups that make the production and perception of the lengthy songs tractable by yielding a set of simple groups that, although arranged in rigid order, can be repeated multiple times to generate the entire song.