Bowhead whales produce one of the most complex songs in the animal kingdom. These hierarchically structured acoustic displays — with notes nested in phrases, phrases in songs, songs in song bouts, and song bouts in song sessions — are thought to be produced by males in mating contexts (Figure 1; Stafford 2022).
Past analysis of songs recorded from the Spitsbergen bowhead whale population showed that bowheads are capable of producing a remarkable number of short-lived, distinct song types (Stafford et al. 2018), but it is unknown whether this trend holds for other populations. Our objective is to quantify the diversity and temporal dynamics of songs produced by Bering-Chukchi-Beaufort (BCB) bowhead whales.
To do so, we are using passive acoustic recordings that were collected via AURAL-M2 recording packages. These recording packages were deployed on a mooring located in the southern Chukchi Sea just north of the Bering Strait (Figure 2).
To start, we are focusing on recordings from a peak singing month (December) in four different years (2011, 2014, 2017, and 2020). Using an acoustic analysis software called Raven Pro, we are visualizing over 900 hours of recordings as spectrograms, annotating song boundaries, and extracting song features, such as duration and frequency range. We manually assign clearly distinguishable songs to types, which then allows us to track song type “lifespans” and diversity within months and across years. While analyses are still ongoing, our initial results suggest that BCB bowhead whales produce a remarkable diversity of short-lived song types, with no song types present in more than one year, and song type lifespans typically on the order of days, occasionally weeks.
Our results to date align with previous work on Spitsbergen bowhead whale song and suggest that rapidly evolving songs are not a population specific trait, but rather a defining feature of what it means to be a bowhead whale in general. This work is helping us better understand a key communicative display for this enigmatic, iconic Arctic species, and is allowing us to establish a foundation for future inter-population song comparisons.
This research is funded by the Oregon Gray Whale License Plate and the L’Oreal USA For Women in Science Program. The acoustic data we are analyzing were collected with support from the National Oceanic and Atmospheric Administration (grant numbers NA10OAR4320148, AM105, and AM133) and the National Science Foundation (award number 2138801).
