Recurrent acoustic patterns produced by a singing humpback whale (Megaptera novaeangliae)

Abstract

Humpback whales (Megaptera novaeangliae) often sing continuously for multiple hours. Little is known about how individual singers vary the acoustic features of their songs within such prolonged song sessions. Here, a case study analysis of a seven-hour singing bout was performed to clarify the consistency with which global acoustic features can be produced by an individual singer. Analyses of 44 consecutive songs within a multi-hour sample revealed that: (1) songs of similar duration may be repeated for at least an hour; (2) frequency content and sequencing can be produced stably for several hours; and (3) multiple, narrow-band tonal streams, possibly song-generated, may co-occur within a song session. These analyses of intra-individual variations in acoustic features within a song session revealed the precision with which a singer can control acoustic fields, raising new questions about the predictability of acoustic variations in songs across different contexts and environmental conditions. The finding of spectral stability over hour-long periods further supports a potentially important functional role for song-generated reverberation and provides a baseline for future quantitative comparisons of song acoustics within and across individual singers.