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

• Published in: Journal of Experimental Biology
• Main Authors: Malinka, Chloe E, Tønnesen, Pernille, Dunn, Charlotte A, Claridge, Diane E, Gridley, Tess, Elwen, Simon H, Teglberg Madsen, Peter
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2021
• Subjects: Beam pattern; Bioacoustics; Hydrophone array; Narrow-band high-frequency; Passive acoustic monitoring; Source parameters; Sperm whale; toothed whales
• Online Access: https://risweb.st-andrews.ac.uk/portal/en/researchoutput/echolocation-click-parameters-and-biosonar-behaviour-of-the-dwarf-sperm-whale-kogia-sima(638f32b0-7260-4fe3-89dc-9cb4680c6ef6).html; https://doi.org/10.1242/jeb.240689; https://research-repository.st-andrews.ac.uk/bitstream/10023/25110/1/Malinka_2021_JEB_Echolocation_click_VoR.pdf; https://journals.biologists.com/jeb/article/224/6/jeb240689/237928/Echolocation-click-parameters-and-biosonar#supplementary-data

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, BW RMS , of 3±1 kHz), with SLs of up to 197 dB re. 1 µPa peak-to-peak (μPa pp ) 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.