Cyclical Variations in Acoustic Features Within the Song Sessions of Humpback Whales (Megaptera novaeangliae)

Song sessions produced by humpback whales recorded off the coasts of Hawaii and Colombia show recurrent patterns of acoustic variation across consecutive songs. Analyses of intra-individual variations within continuous song sessions revealed that songs consistently cycled through stages of acoustic complexity. At time scales spanning tens of minutes, cyclical variations likely reflected the diving behavior of singers. Changes over shorter time frames suggest that singing humpback whales may also systematically modulate the acoustic complexity of individual sounds during song production, both by gradually morphing units and by varying the number of times they repeat sound patterns. Comparable cycles were evident across years and populations. Cyclical variations within song sessions can reveal how much time and energy singers spend producing tonal versus frequency-modulated/broadband elements. Tonal components are generally more difficult to localize spatially but easier to detect over long distances, suggesting that singing humpback whales may dynamically vary sound production in ways that affect both sound transmission and auditory spatial processing.