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Blue whale acoustic behavior off southern California

  • Author(s): Lewis, Leah Allison
  • Advisor(s): Sirovic, Ana
  • et al.
Abstract

The acoustic repertoire of the Northeast Pacific population of blue whales (Balaenoptera musculus) consists of three different sounds: A, B, and D calls. The pulsed A and tonal B calls can be produced singularly or in phrases or songs, while downswept D calls are only produced as singular calls. Although these sounds have been well described, the behavioral context of sound production is poorly understood. To investigate spatial and temporal variability in blue whale call and song usage off southern California, passive acoustic data collected from four High-Frequency Acoustic Recording Packages (HARPs) were analyzed. The acoustic and dive profile data collected through tags deployed on blue whales were also analyzed to describe the behavioral context of sound production. Singular call and phrase production rates were calculated to assess variability in sound type abundances on different spatial, temporal and behavioral scales. Distinct differences in song type preference were apparent, with offshore sites featuring songs comprised of multiple sequential B units following a single A, while inshore, A and B units alternated. Most blue whale sounds were produced during the summer and fall. The majority of all sounds produced by tagged blue whales occurred during non-lunging dives at shallow depths (less than 30 m). Song production was associated with shallow, non-lunging dives, while singular calls often occurred during lunging dives or bouts of surface behavior. The observed differences in blue whale acoustic behavior off southern California will aid in the development of context specific rates for future models of density estimation.

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