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

Chloe E Malinka*, Pernille Tønnesen, Charlotte A Dunn, Diane E Claridge, Tess Gridley, Simon H Elwen, Peter Teglberg Madsen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)
3 Downloads (Pure)

Abstract

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.

Original languageEnglish
Article numberjeb240689
Number of pages16
JournalJournal of Experimental Biology
Volume224
Issue number6
DOIs
Publication statusPublished - 26 Mar 2021

Keywords

  • Beam pattern
  • Bioacoustics
  • Hydrophone array
  • Narrow-band high-frequency
  • Passive acoustic monitoring
  • Source parameters

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