Classification and behavior of free-ranging female southern elephant seal dives based on threedimensional movements and video-recorded observations

McGovern, K.A.; Rodríguez, Diego H.; Lewis, Mirtha; Davis, Randall W.

doi:10.3354/meps12936

Cited by 38 publications

(14 citation statements)

References 79 publications

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“…Recently, McGovern et al ( 2019) obtained head-mounted video records from five female southern elephant seals at Peninsula Valdes, Argentina, and reported a few fish species (myctophids, smelt, dragonfish), but no squid, in the video records. However, no quantitative descriptions on the composition of fish species were available in McGovern et al (2019). These results suggest that the diet of northern and southern elephant seals is broadly similar.…”

Section: Comparison With Other Marine Mammalsmentioning

confidence: 79%

Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals

Yoshino

Takahashi

Adachi

et al. 2020

Journal of Experimental Biology

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Knowledge of the diet of marine mammals is fundamental to understanding their role in marine ecosystems and response to environmental change. Recently, animal-borne video cameras have revealed the diet of marine mammals that make short foraging trips. However, novel approaches that allocate video time to target prey capture events is required to obtain diet information for species that make long foraging trips over great distances. We combined satellite telemetry and depth recorders with newly developed date/time-, depth-, and acceleration-triggered animal-borne video cameras to examine the diet of female northern elephant seals during their foraging migrations across the eastern North Pacific. We obtained 48.2 hours of underwater video, from cameras mounted on the head (n=12) and jaw (n=3) of seals. Fish dominated the diet (78% of 697 prey items recorded) across all foraging locations (range: 37–55°N, 122–150°W), diving depths (range: 238–1167 m) and water temperatures (range: 3.2–7.4 °C), while squid comprised only 7% of the diet. Identified prey included fishes such as myctophids, Merluccius sp., and Icosteus aenigmaticus, and squids such as Histioteuthis sp., Octopoteuthis sp., and Taningia danae. Our results corroborate fatty acid analysis, which also found that fish are more important in the diet and contrasts to stomach content analyses that found cephalopods to be the most important component of the diet. Our work shows that in-situ video observation is a useful method for studying the at-sea diet of long-ranging marine predators.

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Section: Comparison With Other Marine Mammalsmentioning

confidence: 79%

Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals

Yoshino

Takahashi

Adachi

et al. 2020

Journal of Experimental Biology

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“…However, these flashes consistently occurred shortly after a brief, lower intensity jerk peak representing a more subtle movement detected by the accelerometer, e.g. due to a small movement of the head or muscle contractions that expand the whiskers as the seal approaches its prey (McGovern et al, 2019;Naito et al, 2013). The resulting water movement could be mechanically sensed by the prey, inducing it to emit a defence flash (Barnes and Case, 1974).…”

Section: Association Between Flash and Pcamentioning

confidence: 99%

“…However, collecting direct evidence of the prey types targeted by deep-diving marine predators as a function of time and space remains a technological challenge. Animal-borne cameras can potentially be used to identify nekton that are approached closely (McGovern et al, 2019;Naito et al, 2013;Thiebot et al, 2016), providing a definitive description of diet when image quality is good, but short battery lifetimes and the need for an external light source, with its attendant risk of disrupting predator and prey behaviour, limit their utility for long deployments on SES. A more energy efficient but perhaps less definitive approach could be to distinguish prey types on the basis of the bioluminescent signals that they emit, and this may have the added benefit of helping to interpret the sensory cues utilised by their seal predators.…”

Section: Introductionmentioning

confidence: 99%

Flash and grab: deep-diving southern elephant seals trigger anti-predator flashes in bioluminescent prey

Goulet

Guinet

Campagna

et al. 2020

Journal of Experimental Biology

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Bioluminescence, which occurs in approximately 80% of the world's mesopelagic fauna, can take the form of a low-intensity continuous glow (e.g. for counter-illumination or signalling) or fast repetitions of brighter anti-predatory flashes. The southern elephant seal (SES) is a major consumer of mesopelagic organisms, in particular the abundant myctophid fish, yet the fine-scale relationship between this predator's foraging behaviour and bioluminescent prey remains poorly understood. We hypothesised that brief, intense light emissions should be closely connected with prey strikes when the seal is targeting bioluminescent prey that reacts by emitting anti-predator flashes. To test this, we developed a biologging device containing a fast-sampling light sensor together with location and movement sensors to measure simultaneously anti-predator bioluminescent emissions and the predator's attack motions with a 20 ms resolution. Tags were deployed on female SES breeding at Kerguelen Islands and Penıńsula Valdeś, Argentina. In situ light levels in combination with duration of prey capture attempts indicated that seals were targeting a variety of prey types. For some individuals, bioluminescent flashes occurred in a large proportion of prey strikes, with the timing of flashes closely connected with the predator's attack motion, suggestive of antipredator emissions. Marked differences across individuals and location indicate that SES do exploit bioluminescent organisms but the proportion of these in the diet varies widely with location. The combination of wideband light and acceleration data provides new insight into where and when different prey types are encountered and how effectively they might be captured.

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“…Cetaceans spend the vast majority of their lives at various depths below the ocean surface, consequently vertical movement must be considered equally if not more so than horizontal movement to fully understand the ecological significance of animal behavior. Dive behavior of marine mammals may serve a number of functions depending on the structure of the dive and depths targeted, including foraging (Viviant et al, 2014), transiting (McGovern et al, 2019), resting (Wright et al, 2017), aiding digestion (Crocker et al, 1997), reproductive behaviors (Baechler et al, 2002), predator avoidance (Aguilar de Soto et al, 2020), molting (Fortune et al, 2017), and possibly navigation (Matsumura et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Year-Round Dive Characteristics of Male Beluga Whales From the Eastern Beaufort Sea Population Indicate Seasonal Shifts in Foraging Strategies

et al. 2022

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Dive behavior represents multiple ecological functions for marine mammals, but our understanding of dive characteristics is typically limited by the resolution or longevity of tagging studies. Knowledge on the time-depth structures of dives can provide insight into the behaviors represented by vertical movements; furthering our understanding of the ecological importance of habitats occupied, seasonal shifts in activity, and the energetic consequences of targeting prey at a given depth. Given our incomplete understanding of Eastern Beaufort Sea (EBS) beluga whale behavior over an annual cycle, we aimed to characterize dives made by belugas, with a focus on analyzing shifts in foraging strategies. Objectives were to (i) characterize and classify the range of beluga-specific dive types over an annual cycle, (ii) propose dive functions based on optimal foraging theory, physiology, and association with environmental variables, and (iii) identify whether belugas undergo seasonal shifts in the frequency of dives associated with variable foraging strategies. Satellite-linked time-depth-recorders (TDRs) were attached to 13 male belugas from the EBS population in 2018 and 2019, and depth data were collected in time series at a 75 s sampling interval. Tags collected data for between 13 and 357 days, including three tags which collected data across all months. A total of 90,211 dives were identified and characterized by twelve time and depth metrics and classified into eight dive types using a Gaussian mixed modeling and hierarchical clustering analysis approach. Dive structures identify various seasonal behaviors and indicate year-round foraging. Shallower and more frequent diving during winter in the Bering Sea indicate foraging may be energetically cheaper, but less rewarding than deeper diving during summer in the Beaufort Sea and Arctic Archipelago, which frequently exceeded the aerobic dive limit previously calculated for this population. Structure, frequency and association with environmental variables supports the use of other dives in recovery, transiting, and navigating through sea ice. The current study provides the first comprehensive description of the year-round dive structures of any beluga population, providing baseline information to allow improved characterization and to monitor how this population may respond to environmental change and increasing anthropogenic stressors.

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Classification and behavior of free-ranging female southern elephant seal dives based on threedimensional movements and video-recorded observations

Cited by 38 publications

References 79 publications

Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals

Acceleration-triggered animal-borne videos show a dominance of fish in the diet of female northern elephant seals

Flash and grab: deep-diving southern elephant seals trigger anti-predator flashes in bioluminescent prey

Year-Round Dive Characteristics of Male Beluga Whales From the Eastern Beaufort Sea Population Indicate Seasonal Shifts in Foraging Strategies

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