Predictable variability in humpback whale (Megaptera novaeangliae) song acoustics and potential masking of songs by anthropogenic noise

Abstract

Past analyses of humpback whale songs emphasize the flexibility with which whales change their songs across years. Acoustic measurements of song provide a way to systematically assess changes in songs and to predict humpbacks’ ability to adapt to changing soundscapes. Singers concentrate energy at predictable frequencies while continuously adjusting song acoustics. Analyses of songs from the Southeastern Pacific and Central North Pacific stocks (2013–2019) were used to characterize variations in peak frequencies. Preliminary results showed that humpbacks consistently concentrated energy in 3–4 frequency bands, suggesting that this is a universal feature of song production, and that singers may be less flexible in their ability to modify songs than has been assumed. Frequency use was also compared across different locations that vary in boat traffic. Initial findings revealed a negative association between peak frequency and the “noisiness” of a location. Examining patterns of variability in song acoustics may reveal an impact of anthropogenic noise on singing behavior. Predicting how increases in ocean noise may affect song is critical because whales are ecosystem engineers on a global scale. The extensive geographic and temporal coverage of these analyses adds a novel piece to this conservation puzzle.