Foraging strategies of a generalist marine predator inhabiting a dynamic environment

McHuron, Elizabeth A.; Robinson, Patrick W.; Simmons, Samantha E.; Kuhn, Carey E.; Fowler, MA; Costa, Daniel P.

doi:10.1007/s00442-016-3732-0

Cited by 31 publications

(44 citation statements)

References 64 publications

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“…Gliding occasionally occurred in dives shallower than 100 m; however, the glides were brief and inconsistent between these shallower dives. Similar to previous reports on California sea lions from San Nicolas Island Ponganis, 2013, 2014;McHuron et al, 2016), all animals reached depths over 200 m, while the majority (52%) of dives were shallower than 50 m. The distribution of maximum dive depths was bimodal, with very few dives (11%) occurring at depths of 100-150 m. This bimodal pattern influenced how we defined shallow (≤100 m) and deep (>100 m) dives. Dive statistics are reported in Table 1.…”

Section: Resultssupporting

confidence: 86%

“…The following dive phases were identified in the data: descent (surface to 80% maximum depth), bottom (depths within 80% maximum depth) and ascent (80% maximum depth to surface). Most California sea lion dives are shallower than 100 m, yet many adult female California sea lions from San Nicolas Island are known to be deep divers (Kuhn and Costa, 2014;McHuron et al, 2016). Therefore, to compare shallow and deep dives, dives to maximum depths >100 m were classified as deep, and dives to maximum depths ≤100 m were classified as shallow.…”

Section: Data Processing and Statisticsmentioning

confidence: 99%

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Flipper stroke rate and venous oxygen levels in free-ranging California sea lions

Tift

Hückstädt

McDonald

et al. 2017

Journal of Experimental Biology

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The depletion rate of the blood oxygen store, development of hypoxemia and dive capacity are dependent on the distribution and rate of blood oxygen delivery to tissues while diving. Although blood oxygen extraction by working muscle would increase the blood oxygen depletion rate in a swimming animal, there is little information on the relationship between muscle workload and blood oxygen depletion during dives. Therefore, we examined flipper stroke rate, a proxy of muscle workload, and posterior vena cava oxygen profiles in four adult female California sea lions (Zalophus californianus) during foraging trips at sea. Flipper stroke rate analysis revealed that sea lions minimized muscle metabolism with a stroke-glide strategy when diving, and exhibited prolonged glides during the descent of deeper dives (>100 m). During the descent phase of these deep dives, 55± 21% of descent was spent gliding, with the longest glides lasting over 160 s and covering a vertical distance of 340 m. Animals also consistently glided to the surface from 15 to 25 m depth during these deeper dives. Venous hemoglobin saturation (S O2 ) profiles were highly variable throughout dives, with values occasionally increasing during shallow dives. The relationship between S O2 and flipper stroke rate was weak during deeper dives, while this relationship was stronger during shallow dives. We conclude that (1) the depletion of oxygen in the posterior vena cava in deep-diving sea lions is not dependent on stroke effort, and (2) stroke-glide patterns during dives contribute to a reduction of muscle metabolic rate.

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Section: Resultssupporting

confidence: 86%

Section: Data Processing and Statisticsmentioning

confidence: 99%

Flipper stroke rate and venous oxygen levels in free-ranging California sea lions

Tift

Hückstädt

McDonald

et al. 2017

Journal of Experimental Biology

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“…To our knowledge, this is the first study to detect an association between California sea lion foraging habitat and mesoscale activity. Sea lions are known to display extensive intraspecies variability in their at‐sea movements, behaviors, and distributions (Kuhn & Costa, ; McHuron et al., ; Melin et al., ). This is especially true during lactation, as females must continually expand and adjust their foraging behavior in response to prey movements (Melin et al., ) and direct competition for resources under a restricted range and large population size.…”

Section: Discussionmentioning

confidence: 99%

“…Description of animal capture and instrumentation are provided in Kuhn and Costa () and McHuron et al. ().…”

Section: Methodsmentioning

confidence: 99%

“…While a robust body of literature has documented the biology, ecology, and physiology of female California sea lions (Antonelis, Stewart, & Perryman, ; Costa, ; Feldkamp, DeLong, & Antonelis, ; McDonald & Ponganis, ; McHuron et al., ; Melin et al., ; Villegas‐Amtmann et al., , ), these studies focused on foraging characteristics such as dive behavior, trip length, and duration of individuals from a single rookery or in response to El Niño events (Antonelis et al., ; Costa, ; Melin, Orr, Harris, Laake, & DeLong, ; Melin et al., ; Ono et al., ; Sydeman & Allen, ; Trillmich et al., ). Although aspects of at‐sea habitat use have been explored (Kuhn & Costa, ), our ability to broadly identify suitable foraging habitat of this central‐place forager has been limited.…”

Section: Introductionmentioning

confidence: 99%

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Characterizing habitat suitability for a central‐place forager in a dynamic marine environment

Briscoe

Fossette

Scales

et al. 2018

Ecology and Evolution

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Characterizing habitat suitability for a marine predator requires an understanding of the environmental heterogeneity and variability over the range in which a population moves during a particular life cycle. Female California sea lions (Zalophus californianus) are central‐place foragers and are particularly constrained while provisioning their young. During this time, habitat selection is a function of prey availability and proximity to the rookery, which has important implications for reproductive and population success. We explore how lactating females may select habitat and respond to environmental variability over broad spatial and temporal scales within the California Current System. We combine near‐real‐time remotely sensed satellite oceanography, animal tracking data (n = 72) from November to February over multiple years (2003–2009) and Generalized Additive Mixed Models (GAMMs) to determine the probability of sea lion occurrence based on environmental covariates. Results indicate that sea lion presence is associated with cool (<14°C), productive waters, shallow depths, increased eddy activity, and positive sea‐level anomalies. Predictive habitat maps generated from these biophysical associations suggest winter foraging areas are spatially consistent in the nearshore and offshore environments, except during the 2004–2005 winter, which coincided with an El Niño event. Here, we show how a species distribution model can provide broadscale information on the distribution of female California sea lions during an important life history stage and its implications for population dynamics and spatial management.

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The energetic consequences of behavioral variation in a marine carnivore

McHuron

Peterson

Hückstädt

et al. 2018

Ecology and Evolution

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Intraspecific variability in foraging behavior has been documented across a range of taxonomic groups, yet the energetic consequences of this variation are not well understood for many species. Understanding the effect of behavioral variation on energy expenditure and acquisition is particularly crucial for mammalian carnivores because they have high energy requirements that place considerable pressure on prey populations. To determine the influence of behavior on energy expenditure and balance, we combined simultaneous measurements of at‐sea field metabolic rate (FMR) and foraging behavior in a marine carnivore that exhibits intraspecific behavioral variation, the California sea lion (Zalophus californianus). Sea lions exhibited variability in at‐sea FMR, with some individuals expending energy at a maximum of twice the rate of others. This variation was in part attributable to differences in diving behavior that may have been reflective of diet; however, this was only true for sea lions using a foraging strategy consisting of epipelagic (<200 m within the water column) and benthic dives. In contrast, sea lions that used a deep‐diving foraging strategy all had similar values of at‐sea FMR that were unrelated to diving behavior. Energy intake did not differ between foraging strategies and was unrelated to energy expenditure. Our findings suggest that energy expenditure in California sea lions may be influenced by interactions between diet and oxygen conservation strategies. There were no apparent energetic trade‐offs between foraging strategies, although there was preliminary evidence that foraging strategies may differ in their variability in energy balance. The energetic consequences of behavioral variation may influence the reproductive success of female sea lions and result in differential impacts of individuals on prey populations. These findings highlight the importance of quantifying the relationships between energy expenditure and foraging behavior in other carnivores for studies addressing fundamental and applied physiological and ecological questions.

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Foraging strategies of a generalist marine predator inhabiting a dynamic environment

Cited by 31 publications

References 64 publications

Flipper stroke rate and venous oxygen levels in free-ranging California sea lions

Flipper stroke rate and venous oxygen levels in free-ranging California sea lions

Characterizing habitat suitability for a central‐place forager in a dynamic marine environment

The energetic consequences of behavioral variation in a marine carnivore

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