Echolocation click parameters and biosonar behaviour of the dwarf sperm whale (Kogia sima)

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DOI

  • Chloe Elizabeth Malinka
  • Pernille Helene Tønnesen
  • Charlotte A. Dunn, Bahamas Marine Mammal Research Organization (BMMRO), University of St Andrews
  • ,
  • Diane E. Claridge, Bahamas Marine Mammal Research Organization (BMMRO), University of St Andrews
  • ,
  • Tess Gridley, Stellenbosch University, Sea Search Research and Conservation, Sydafrika
  • Simon H. Elwen, Stellenbosch University, Sea Search Research and Conservation, Sydafrika
  • Professor Peter Teglberg Madsen
Dwarf sperm whales (Kogia sima) are small toothed whales that produce narrow-band high-frequency (NBHF) echolocation clicks. Such NBHF clicks, subject to high levels of acoustic absorption, are usually produced by small, shallow-diving odontocetes, such as porpoises, in keeping with their short-range echolocation and fast click rates. Here, we sought to address the problem of how the little-studied and deep-diving Kogia can hunt with NBHF clicks in the deep sea. Specifically, we tested the hypotheses that Kogia produce NBHF clicks with longer inter-click intervals (ICIs), higher directionality and higher source levels (SLs) compared with other NBHF species. We did this by deploying an autonomous deep-water vertical hydrophone array in the Bahamas, where no other NBHF species are present, and by taking opportunistic recordings of a close-range Kogia sima in a South African harbour. Parameters from on-axis clicks (n=46) in the deep revealed very narrow-band clicks (root mean squared bandwidth, BWRMS, of 3±1 kHz), with SLs of up to 197 dB re. 1 µPa peak-to-peak (μPapp) at 1 m, and a half-power beamwidth of 8.8 deg. Their ICIs (mode of 245 ms) were much longer than those of porpoises (<100 ms), suggesting an inspection range that is longer than detection ranges of single prey, perhaps to facilitate auditory streaming of a complex echo scene. On-axis clicks in the shallow harbour (n=870) had ICIs and SLs in keeping with source parameters of other NBHF cetaceans. Thus, in the deep, dwarf sperm whales use a directional, but short-range echolocation system with moderate SLs, suggesting a reliable mesopelagic prey habitat.
OriginalsprogEngelsk
Artikelnummerjeb240689
TidsskriftJournal of Experimental Biology
Vol/bind224
Nummer6
Antal sider16
DOI
StatusUdgivet - mar. 2021

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