A Quantitative Analysis of the Sounds of Hector's Dolphin

Authors

  • Dr. Stephen M. Dawson,

    Corresponding author
    1. Cetos Research, Zoology Department, University of Canterbury, Christchurch
    2. Signal Processing Group, Department of Electrical Engineering, University of Canterbury, Christchurch
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  • C. William Thorpe

    1. Cetos Research, Zoology Department, University of Canterbury, Christchurch
    2. Signal Processing Group, Department of Electrical Engineering, University of Canterbury, Christchurch
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Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand.

Abstract

We developed an automatic, computer-based system in which digital signal processing techniques were used to measure 31 variables from digitized Hector's dolphin (Cephalorhynchus hectori) sounds. Principal component analyses of these data were used to investigate the relationships between sounds. Hector's dolphins make only a very few types of pulsed “clicks”, most of which are centred around 125 kHz. None of these had an average frequency of less than 82 kHz, and the only audible sounds were made up of high-frequency clicks repeated at such high rates that the repetition rate was audible to us as a tonal “cry” or “squeal”. In comparison to signal levels recorded from other cetaceans, all the Hector's dolphin signals were low-level; the maximum received sound pressure level was 163 dB (re 1μPa).

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