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

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.

Sowerby's beaked whale biosonar and movement strategy indicate deep-sea foraging niche differentiation in mesoplodont whales

“…On the face of it, production of echolocation clicks with a high centre frequency, and therefore greater sound absorption, seems like a poor choice for a deep-diving predator that would benefit from long-range patch assessment ( Malinka et al, 2021 ). Unlike sperm whales ( Physeter macrocephalus ) but similar to Blainville's beaked whales, Sowerby's beaked whales begin clicking when they are already deep in the foraging dive and make their first prey capture attempt relatively soon thereafter.…”

Estimating energetic intake for marine mammal bioenergetic models

“…Foraging buzzes (with or without estimates of jerk) have been quantified in beaked whales (Family Ziphiidae ) ( Johnson et al ., 2006 ; Stimpert et al ., 2014 ; Siegal, 2020 ; Alcázar-Treviño et al ., 2021 ; Visser et al ., 2022 ), sperm whales (including Kogia spp. ) ( Fais et al ., 2016 ; Tønnesen et al ., 2020 ; Malinka et al ., 2021 ), short-finned pilot whales ( Globicephala macrorhynchus ) ( Aguilar Soto et al ., 2008 ; Holt et al ., 2021 ), narwhals ( Monodon monoceros ) ( Ngô et al ., 2021 ), smaller delphinids ( Wisniewska et al ., 2014 ; Arranz et al ., 2016 ) and harbour porpoises ( Phocoena phocoena ) ( Wisniewska et al ., 2014 ; Wisniewska et al ., 2018 ).…”

An Acoustic Survey of Beaked Whales and Kogia spp. in the Mariana Archipelago Using Drifting Recorders

“…Kogia spp. have been observed echolocating near the surface Malinka et al, 2021) and their vocal behavior during foraging dives is not understood; therefore, we used a break in detections of one or more 2-min detection files to indicate a new acoustic encounter. Due to the duty cycled data collection, it is not possible to examine the specific start and stop time of each acoustic encounter as echolocation signals may have begun or ended during a period with no recording, resulting in acoustic encounter duration lasting 0-6 additional minutes.…”

“…In addition, the slow drift rate and reduced noise levels allow for increased opportunities to detect the short wavelength and highly directional NBHF clicks produced by Kogia spp. Griffiths et al, 2020;Malinka et al, 2021).…”