scholarly journals Influence of hunting strategy on foraging efficiency in Galapagos sea lions

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11206
Author(s):  
Jessica-Anne Blakeway ◽  
John P.Y. Arnould ◽  
Andrew J. Hoskins ◽  
Patricia Martin-Cabrera ◽  
Grace J. Sutton ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Energy Expenditure ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Foraging Efficiency ◽  
Flat Bottom ◽  
Sea Lions ◽  
Dive Behaviour ◽  
Zalophus Wollebaeki ◽  
Depth Ranges

The endangered Galapagos sea lion (GSL, Zalophus wollebaeki) exhibits a range of foraging strategies utilising various dive types including benthic, epipelagic and mesopelagic dives. In the present study, potential prey captures (PPC), prey energy consumption and energy expenditure in lactating adult female GSLs (n = 9) were examined to determine their foraging efficiency relative to the foraging strategy used. Individuals displayed four dive types: (a) epipelagic (<100 m; EP); or (b) mesopelagic (>100 m; MP) with a characteristic V-shape or U-shape diving profile; and (c) shallow benthic (<100 m; SB) or (d) deep benthic (>100 m; DB) with square or flat-bottom dive profiles. These dive types varied in the number of PPC, assumed prey types, and the energy expended. Prey items and their energetic value were assumed from previous GSL diet studies in combination with common habitat and depth ranges of the prey. In comparison to pelagic dives occurring at similar depths, when diving benthically, GSLs had both higher prey energy consumption and foraging energy expenditure whereas PPC rate was lower. Foraging efficiency varied across dive types, with benthic dives being more profitable than pelagic dives. Three foraging trip strategies were identified and varied relative to prey energy consumed, energy expended, and dive behaviour. Foraging efficiency did not significantly vary among the foraging trip strategies suggesting that, while individuals may diverge into different foraging habitats, they are optimal within them. These findings indicate that these three strategies will have different sensitivities to habitat-specific fluctuations due to environmental change.

scholarly journals Diving deep into trouble: the role of foraging strategy and morphology in adapting to a changing environment

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Monique Ladds ◽  
David Rosen ◽  
Carling Gerlinsky ◽  
David Slip ◽  
Robert Harcourt
Keyword(s):  
Foraging Strategy ◽  
Central Place ◽  
Dive Duration ◽  
Foraging Strategies ◽  
Body Morphology ◽  
Sea Lions ◽  
Fur Seals ◽  
Adequate Food ◽  
Physiological Capacity ◽  
Total Body Oxygen

Abstract Physiology places constraints on an animal’s ability to forage and those unable to adapt to changing conditions may face increased challenges to reproduce and survive. As the global marine environment continues to change, small, air-breathing, endothermic marine predators such as otariids (fur seals and sea lions) and particularly females, who are constrained by central place foraging during breeding, may experience increased difficulties in successfully obtaining adequate food resources. We explored whether physiological limits of female otariids may be innately related to body morphology (fur seals vs sea lions) and/or dictate foraging strategies (epipelagic vs mesopelagic or benthic). We conducted a systematic review of the increased body of literature since the original reviews of Costa et al. (When does physiology limit the foraging behaviour of freely diving mammals? Int Congr Ser 2004;1275:359–366) and Arnould and Costa (Sea lions in drag, fur seals incognito: insights from the otariid deviants. In Sea Lions of the World Fairbanks. Alaska Sea Grant College Program, Alaska, USA, pp. 309–324, 2006) on behavioural (dive duration and depth) and physiological (total body oxygen stores and diving metabolic rates) parameters. We estimated calculated aerobic dive limit (cADL—estimated duration of aerobic dives) for species and used simulations to predict the proportion of dives that exceeded the cADL. We tested whether body morphology or foraging strategy was the primary predictor of these behavioural and physiological characteristics. We found that the foraging strategy compared to morphology was a better predictor of most parameters, including whether a species was more likely to exceed their cADL during a dive and the ratio of dive time to cADL. This suggests that benthic and mesopelagic divers are more likely to be foraging at their physiological capacity. For species operating near their physiological capacity (regularly exceeding their cADL), the ability to switch strategies is limited as the cost of foraging deeper and longer is disproportionally high, unless it is accompanied by physiological adaptations. It is proposed that some otariids may not have the ability to switch foraging strategies and so be unable adapt to a changing oceanic ecosystem.

scholarly journals Optimal Lévy-flight foraging in a finite landscape

2015 ◽  
Vol 12 (104) ◽  
pp. 20141158 ◽  
Author(s):  
Kun Zhao ◽  
Raja Jurdak ◽  
Jiajun Liu ◽  
David Westcott ◽  
Branislav Kusy ◽  
...  
Keyword(s):  
Power Law ◽  
Animal Movement ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Foraging Efficiency ◽  
Lévy Flight ◽  
Step Size ◽  
Levy Flight ◽  
Ballistic Motion ◽  
Wide Range

We present a simple model to study Lévy-flight foraging with a power-law step-size distribution in a finite landscape with countable targets. We find that different optimal foraging strategies characterized by a wide range of power-law exponent μ opt , from ballistic motion ( μ opt → 1) to Lévy flight (1 < μ opt < 3) to Brownian motion ( μ opt ≥ 3), may arise in adaptation to the interplay between the termination of foraging, which is regulated by the number of foraging steps, and the environmental context of the landscape, namely the landscape size and number of targets. We further demonstrate that stochastic returning can be another significant factor that affects the foraging efficiency and optimality of foraging strategy. Our study provides a new perspective on Lévy-flight foraging, opens new avenues for investigating the interaction between foraging dynamics and the environment and offers a realistic framework for analysing animal movement patterns from empirical data.

Spatial variation in the foraging behaviour of the Galapagos sea lions (Zalophus wollebaeki) assessed using scat collections and stable isotope analysis

2013 ◽  
Vol 94 (6) ◽  
pp. 1099-1107 ◽  
Author(s):  
Diego Páez-Rosas ◽  
David Aurioles-Gamboa
Keyword(s):  
Feeding Habits ◽  
Isotope Analysis ◽  
Space Time ◽  
Trophic Niche ◽  
Foraging Strategies ◽  
Scat Analysis ◽  
Sea Lions ◽  
Fluctuating Resources ◽  
Zalophus Wollebaeki ◽  
Time Changes

This study focuses on the comparative analysis of variables related to the trophic niche plasticity in the Galapagos sea lion (Zalophus wollebaeki). There is great concern regarding the future of this species, so study of the diet and the way these animals obtain their food is useful to understand and predict their survival possibilities in the long term. The combined use of scat analysis and stable isotopes helps to determine foraging habits of this species in greater detail. The objective of the study was to assess the feeding habits of Z. wollebaeki and its space–time variation. The scat analysis (n = 200) gave as a result space–time changes in the foraging strategies of this species. The isotopic values (n = 80) showed differences in relation to foraging grounds (δ13C: P = 0.001), but also suggested an apparent stability in the trophic level of their diet (δ15N: P = 0.084). These results constitute a relevant finding in the evolutionary behaviour of the species, showing that Z. wollebaeki has developed a high degree of plasticity in its foraging habits that may improve its survival in a highly demanding ecosystem in terms of limited and fluctuating resources.

Stable isotope signatures of whisker and blood serum confirm foraging strategies for female New Zealand sea lions (Phocarctos hookeri) derived from telemetry

2017 ◽  
Vol 95 (12) ◽  
pp. 955-963 ◽  
Author(s):  
B.L. Chilvers
Keyword(s):  
New Zealand ◽  
Stable Isotope ◽  
Isotopic Composition ◽  
Blood Serum ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Female Population ◽  
Sea Lions ◽  
Stable Isotope Signatures ◽  
Phocarctos Hookeri

Recognizing the individual variability of foraging behaviour of marine predators is important for understanding their role in the marine ecosystem and identifying how species may respond to environmental variability or human impacts. This research examines stable isotope signatures (δ13C and δ15N) of blood serum and whiskers from 22 female New Zealand sea lions (Phocarctos hookeri (Gray, 1844)) to determine if the isotopic composition of serum reflects foraging strategy, and whether serum and proximal whisker growth have similar signatures, therefore indicating the isotopic composition of whiskers also reflects the foraging strategy diet at the time of their growth. Female New Zealand sea lions are known to have two distinct foraging strategies (mesopelagic or benthic ecotypes), shown to be habitual within and between years. Females who are known to be mesopelagic foragers have higher overlap and are at greater risk of harmful interactions with fisheries. This research found that the two foraging strategies identified from telemetry are also associated with different δ13C and δ15N isotopic values from blood serum and whiskers. Therefore, stable isotope analysis could be used to determine the proportion of the female population that are likely to be exposed to the detrimental direct and indirect interactions with fisheries.

scholarly journals Be different to be better: the effect of personality on optimal foraging with incomplete knowledge

2021 ◽  
Author(s):  
Poppy M. Jeffries ◽  
Samantha C. Patrick ◽  
Jonathan R. Potts
Keyword(s):  
Optimal Foraging ◽  
Optimal Foraging Theory ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Partial Knowledge ◽  
Marginal Value ◽  
Animal Populations ◽  
Plausible Mechanism ◽  
Insight Into ◽  
Modelling Approach

AbstractMany animal populations include a diversity of personalities, and these personalities are often linked to foraging strategy. However, it is not always clear why populations should evolve to have this diversity. Indeed, optimal foraging theory typically seeks out a single optimal strategy for individuals in a population. So why do we, in fact, see a variety of strategies existing in a single population? Here, we aim to provide insight into this conundrum by modelling the particular case of foraging seabirds, that forage on patchy prey. These seabirds have only partial knowledge of their environment: they do not know exactly where the next patch will emerge, but they may have some understanding of which locations are more likely to lead to patch emergence than others. Many existing optimal foraging studies assume either complete knowledge (e.g. Marginal Value Theorem) or no knowledge (e.g. Lévy Flight Hypothesis), but here we construct a new modelling approach which incorporates partial knowledge. In our model, different foraging strategies are favoured by different birds along the bold-shy personality continuum, so we can assess the optimality of a personality type. We show that it is optimal to be shy (resp. bold) when living in a population of bold (resp. shy) birds. This observation gives a plausible mechanism behind the emergence of diverse personalities. We also show that environmental degradation is likely to favour shyer birds and cause a decrease in diversity of personality over time.

Health Status of Galápagos Sea Lions (Zalophus wollebaeki) on San Cristóbal Island Rookeries Determined by Hematology, Biochemistry, Blood Gases, and Physical Examination

2016 ◽  
Vol 52 (1) ◽  
pp. 100-105 ◽  
Author(s):  
Diego Páez-Rosas ◽  
Maximilian Hirschfeld ◽  
Diane Deresienski ◽  
Gregory A. Lewbart
Keyword(s):  
Health Status ◽  
Physical Examination ◽  
Blood Gases ◽  
Sea Lions ◽  
Zalophus Wollebaeki

scholarly journals Change in the foraging strategy of female South American sea lions (Carnivora: Pinnipedia) after parturition

2010 ◽  
Vol 74 (3) ◽  
pp. 589-598 ◽  
Author(s):  
Massimiliano Drago ◽  
Luís Cardona ◽  
Enrique A. Crespo ◽  
Néstor García ◽  
Santiago Ameghino ◽  
...  
Keyword(s):  
Foraging Strategy ◽  
South American ◽  
Sea Lions

scholarly journals Blue whales (Balaenoptera musculus) optimize foraging efficiency by balancing oxygen use and energy gain as a function of prey density

2015 ◽  
Vol 1 (9) ◽  
pp. e1500469 ◽  
Author(s):  
Elliott Lee Hazen ◽  
Ari Seth Friedlaender ◽  
Jeremy Arthur Goldbogen
Keyword(s):  
Energy Intake ◽  
Prey Density ◽  
Prey Capture ◽  
Energy Gain ◽  
Foraging Strategies ◽  
Foraging Efficiency ◽  
Energetic Efficiency ◽  
Breath Hold ◽  
Balaenoptera Musculus ◽  
Blue Whales

Terrestrial predators can modulate the energy used for prey capture to maximize efficiency, but diving animals face the conflicting metabolic demands of energy intake and the minimization of oxygen depletion during a breath hold. It is thought that diving predators optimize their foraging success when oxygen use and energy gain act as competing currencies, but this hypothesis has not been rigorously tested because it has been difficult to measure the quality of prey that is targeted by free-ranging animals. We used high-resolution multisensor digital tags attached to foraging blue whales (Balaenoptera musculus) with concurrent acoustic prey measurements to quantify foraging performance across depth and prey density gradients. We parameterized two competing physiological models to estimate energy gain and expenditure based on foraging decisions. Our analyses show that at low prey densities, blue whale feeding rates and energy intake were low to minimize oxygen use, but at higher prey densities feeding frequency increased to maximize energy intake. Contrary to previous paradigms, we demonstrate that blue whales are not indiscriminate grazers but instead switch foraging strategies in response to variation in prey density and depth to maximize energetic efficiency.

scholarly journals Mixing it up in Alaska: Habitat use of adult female Steller sea lions reveals a variety of foraging strategies

Ecosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Michelle E. Lander ◽  
Brian S. Fadely ◽  
Thomas S. Gelatt ◽  
Jeremy T. Sterling ◽  
Devin S. Johnson ◽  
...  
Keyword(s):  
Habitat Use ◽  
Adult Female ◽  
Foraging Strategies ◽  
Steller Sea Lions ◽  
Sea Lions
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