Humpback whale song hierarchical structure: Historical context and discussion of current classification issues

Authors

  • Danielle M. Cholewiak,

    Corresponding authorCurrent affiliation:
    1. Protected Species Branch, Northeast Fisheries Science Center/NOAA/NMFS, Woods Hole, Massachusetts, U.S.A
    • Department of Neurobiology and Behavior and Bioacoustics Research Program, Cornell University, Ithaca, New York, U.S.A
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  • Renata S. Sousa-Lima,

    1. Field of Zoology and Bioacoustics Research Program, Cornell University, Ithaca, New York, U.S.A
    2. Instituto Baleia Jubarte, Caravelas, Bahia, Brazil
    Current affiliation:
    1. LaB – Laboratório de Bioacústica/Bioacoustics Lab, Departamento de Fisiologia/Department of Physiology, Centro de Biociências/Biosciences Center, Universidade Federal do Rio Grande do Norte/Federal University of Rio Grande do Norte, Natal, RN, Brazil
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  • Salvatore Cerchio

    1. Wildlife Conservation Society, Global Conservation, Ocean Giants Program, Bronx, New York, U.S.A
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Corresponding author (e-mail: danielle.cholewiak@noaa.gov).

Abstract

Consistent and well-defined criteria for the classification and measurement of humpback whale song features are essential for robust comparisons between investigators. Song structure terminology has been well-established and used by many authors, though at times inconsistently. This review discusses the development of the nomenclature describing humpback song and explores the potential significance of the often-overlooked variation in song patterns. Within the hierarchical definition of humpback song, the most problematic issues arise from the inconsistent delineation of phrase types, and the use of the metric of song duration without regards to variability in thematic sequence. With regards to the former, a set of guidelines is suggested to facilitate consistent delineation of phrases. With regards to the latter, current research demonstrates that the “song duration” metric has resulted in the disregard of variability at this level, which is more widespread than traditionally reported. An exemplar case is used to highlight the problem inherent in defining and measuring song duration. Humpback song is evaluated within the framework of avian songbird research, and a shift in analysis paradigm is recommended, towards phrase-based analyses in which sequences of phrases are treated as a salient feature of song pattern.

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