Heard but not seen: Occurrence of<i>Kogia</i>spp. along the western North Atlantic shelf break

Hodge, Lynne; Baumann‐Pickering, Simone; Hildebrand, John A.; Bell, Joel T.; Cummings, Erin W.; Foley, Heather J.; McAlarney, Ryan J.; McLellan, William A.; Pabst, D. Ann; Swaim, Zachary T.; Waples, Danielle M.; Read, Andrew J.

doi:10.1111/mms.12498

Cited by 11 publications

(11 citation statements)

References 29 publications

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“…They are not easily approached using a small boat and have thus far eluded tagging attempts in the field (Baird, 2015). A recent study using passive acoustic monitoring (Hodge et al, 2018) found that Kogia may be more common than suggested by the visual survey record alone.…”

Section: Introductionmentioning

confidence: 99%

Assessing Seasonality and Density From Passive Acoustic Monitoring of Signals Presumed to be From Pygmy and Dwarf Sperm Whales in the Gulf of Mexico

et al. 2019

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Pygmy sperm whales (Kogia breviceps) and dwarf sperm whales (Kogia sima) are deep diving cetaceans that commonly strand along the coast of the southeast US, but that are difficult to study visually at sea because of their elusive behavior. Conventional visual surveys are thought to significantly underestimate the presence of Kogia and they have proven difficult to approach for tracking and tagging. An approach is presented for density estimation of signals presumed to be from Kogia spp. based on passive acoustic monitoring data collected at sites in the Gulf of Mexico (GOM) from the period following the Deepwater Horizon oil spill (2010-2013). Both species of Kogia are known to inhabit the GOM, although it is not possible to acoustically separate the two based on available knowledge of their echolocation clicks. An increasing interannual density trend is suggested for animals near the primary zone of impact of the oil spill, and to the southeast of the spill. Densities were estimated based on both counting individual echolocation clicks and counting the presence of groups of animals during one-min time windows. Densities derived from acoustic monitoring at three sites are all substantially higher (4-16 animals/1000 km 2) than those that have been derived for Kogia from line transect visual surveys in the same region (0.5 animals/1000 km 2). The most likely explanation for the observed discrepancy is that the visual surveys are underestimating Kogia spp. density, due to the assumption of perfect detectability on the survey trackline. We present an alternative approach for density estimation, one that derives echolocation and behavioral parameters based on comparison of modeled and observed sound received levels at sites of varying depth.

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Section: Introductionmentioning

confidence: 99%

Assessing Seasonality and Density From Passive Acoustic Monitoring of Signals Presumed to be From Pygmy and Dwarf Sperm Whales in the Gulf of Mexico

et al. 2019

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“…In deep water, the Kogia clicks were only recorded during two array deployments when the maximum hydrophone depth was ∼95 m, and during these periods, Kogia were localized to a maximum depth of 392 m (Table 1). As Kogia are thought to dive deeper than this, and have been recorded on PAM instruments at depths of ∼1000 m (Hodge et al, 2018), it is possible that higher SLs are instead employed at greater depths than those we recorded at, or when descending towards the prey layer, during which a vertical array may not receive powerful on-axis clicks. While the majority (69%) of our sampling effort was when the deepest channel on the array was at ∼300 m, no Kogia clicks were recorded on any of these deeper deployments, so perhaps our deployments were not deep enough, or our sampling effort of nearly 75 h was not enough to capture the full SL dynamic range.…”

Section: Source Level and Biosonar Detection Rangesmentioning

confidence: 82%

“…However, the long ICIs in Kogia are not hard-wired: the relatively long median ICI of >200 ms is over twice the ICI of Kogia observed by PAM in deep-water environments (e.g. Hodge et al, 2018;Hildebrand et al, 2019). Note that the secondary peak in the ICI histogram (Fig.…”

Section: Icis and Inferred Inspection Rangesmentioning

confidence: 87%

“…peak frequency, bandwidth, duration, etc.) have been reported from stranded Kogia held in captivity for rehabilitation (Thomas et al, 1990;Ridgway and Carder, 2001;Marten, 2000;Madsen et al, 2005a) and from recent single-channel field recordings Hodge et al, 2018;Hildebrand et al, 2019;Griffiths et al, 2020). Here, we sought to obtain a deeper quantitative understanding of how Kogia can echolocate to find deep-sea prey using clicks with spectral properties suited for short-range echolocation.…”

Section: Introductionmentioning

confidence: 97%

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

Malinka

Tønnesen

Dunn

et al. 2021

Journal of Experimental Biology

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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.

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“…In contrast to plants, coral reefs, plankton, and invertebrates, marine megafauna is highly mobile and hard to capture. For example, some rare and cryptic marine mammals, such as the dwarf sperm whale Kogia sima and the franciscana dolphin Pontoporia blainvillei are difficult to detect in the field (Moura et al, 2009;Hodge et al, 2018). For these types of organisms, it is challenging, if not impossible, to measure traits such as food intake rate and metabolic rate.…”

Section: Future Perspectivementioning

confidence: 99%

Traits Shared by Marine Megafauna and Their Relationships With Ecosystem Functions and Services

et al. 2019

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Traditional ecological research has focused on taxonomic units to better understand the role of organisms in marine ecosystems. This approach has significantly contributed to our understanding of how species interact with each other and with the physical environment and has led to relevant site-specific conservation strategies. However, this taxonomic-based approach can limit a mechanistic understanding of how environmental change affects marine megafauna, here defined as large fishes (e.g., shark, tuna, and billfishes), sea turtles, marine mammals, and seabirds. Alternatively, an approach based on traits, i.e., measurable behavioral, physiological, or morphological characteristics of organisms, can shed new light on the processes influencing structure and functions of biological communities. Here we review 33 traits that are measurable and comparable among marine megafauna. The variability of these traits within the organisms considered controls functions mainly related to nutrient storage and transport, trophic-dynamic regulations of populations, and community shaping. To estimate the contributions of marine megafauna to ecosystem functions and services, traits can be quantified categorically or over a continuous scale, but the latter is preferred to make comparisons across groups. We argue that the most relevant traits to comparatively study marine megafauna groups are body size, body mass, dietary preference, feeding strategy, metabolic rate, and dispersal capacity. These traits can be used in combination with information on population abundances to predict how changes in the environment can affect community structure, ecosystem functioning, and ecosystem services.

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Heard but not seen: Occurrence ofKogiaspp. along the western North Atlantic shelf break

Cited by 11 publications

References 29 publications

Assessing Seasonality and Density From Passive Acoustic Monitoring of Signals Presumed to be From Pygmy and Dwarf Sperm Whales in the Gulf of Mexico

Assessing Seasonality and Density From Passive Acoustic Monitoring of Signals Presumed to be From Pygmy and Dwarf Sperm Whales in the Gulf of Mexico

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

Traits Shared by Marine Megafauna and Their Relationships With Ecosystem Functions and Services

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