Influence of shelf oceanographic variability on alternate foraging strategies in long-nosed fur seals

2019 ◽  
Vol 615 ◽  
pp. 189-204 ◽  
Author(s):  
D Foo ◽  
C McMahon ◽  
M Hindell ◽  
S Goldsworthy ◽  
F Bailleul
Keyword(s):  
Foraging Strategies ◽  
Fur Seals

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.

Spatial segregation and the influence of habitat on the foraging behavior of northern fur seals (Callorhinus ursinus)

2014 ◽  
Vol 92 (10) ◽  
pp. 861-873 ◽  
Author(s):  
C.E. Kuhn ◽  
R.R. Ream ◽  
J.T. Sterling ◽  
J.R. Thomason ◽  
R.G. Towell
Keyword(s):  
Conservation Strategy ◽  
Foraging Strategies ◽  
Habitat Segregation ◽  
Callorhinus Ursinus ◽  
Foraging Habitat ◽  
Northern Fur Seal ◽  
Dive Behavior ◽  
Fur Seals ◽  
Fur Seal ◽  
Northern Fur Seals

Central place foraging by colonial breeders can lead to depleted prey resources around breeding areas. Segregation of foraging areas both within and between large colonies may act as a mechanism to reduce competition for prey resulting in increased foraging success. We reassessed horizontal (spatial) foraging habitat segregation for northern fur seals (Callorhinus ursinus (L., 1758)) within and between colonies on the Pribilof Islands, Alaska (St. Paul and St. George islands), after the population declined by approximately 40%. Additionally, we examined vertical habitat segregation, where foraging ranges overlapped, and describe the influence of different foraging habitats on northern fur seal dive behavior. Spatial habitat segregation in northern fur seal foraging areas occurred between islands but was variable within islands, which is similar to the pattern previously described. There was no evidence for vertical habitat segregation when fur seals from different rookeries on St. George Island used the same foraging area. Additionally, fur seals from St. Paul Island rookeries that foraged in similar habitats showed fewer differences in dive behavior, indicating that foraging habitat plays a significant role in shaping dive behavior. The use of multiple foraging strategies within the Pribilof Island fur seal population could indicate that a complex management and conservation strategy may be necessary to stop the continuing decline of this population.

scholarly journals The Sun, Moon, Wind, and Biological Imperative–Shaping Contrasting Wintertime Migration and Foraging Strategies of Adult Male and Female Northern Fur Seals (Callorhinus ursinus)

PLoS ONE ◽  
2014 ◽  
Vol 9 (4) ◽  
pp. e93068 ◽  
Author(s):  
Jeremy T Sterling ◽  
Alan M. Springer ◽  
Sara J. Iverson ◽  
Shawn P. Johnson ◽  
Noel A. Pelland ◽  
...  
Keyword(s):  
Adult Male ◽  
Foraging Strategies ◽  
Callorhinus Ursinus ◽  
The Sun ◽  
Male And Female ◽  
Fur Seals ◽  
Northern Fur Seals

scholarly journals Long-Term Species, Sexual and Individual Variations in Foraging Strategies of Fur Seals Revealed by Stable Isotopes in Whiskers

PLoS ONE ◽  
2012 ◽  
Vol 7 (3) ◽  
pp. e32916 ◽  
Author(s):  
Laëtitia Kernaléguen ◽  
Bernard Cazelles ◽  
John P. Y. Arnould ◽  
Pierre Richard ◽  
Christophe Guinet ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Foraging Strategies ◽  
Fur Seals ◽  
Individual Variations

scholarly journals The cost of a meal: factors influencing prey profitability in Australian fur seals

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12608
Author(s):  
Nelle Meyers ◽  
Cassie N. Speakman ◽  
Nicole A.S.-Y. Dorville ◽  
Mark A. Hindell ◽  
Jayson M. Semmens ◽  
...  
Keyword(s):  
Environmental Variability ◽  
Prey Type ◽  
Video Data ◽  
Foraging Strategies ◽  
Costs And Benefits ◽  
Fur Seals ◽  
Data Loggers ◽  
Eastern Australia ◽  
Survival And Reproduction ◽  
Gross Energy

Knowledge of the factors shaping the foraging behaviour of species is central to understanding their ecosystem role and predicting their response to environmental variability. To maximise survival and reproduction, foraging strategies must balance the costs and benefits related to energy needed to pursue, manipulate, and consume prey with the nutritional reward obtained. While such information is vital for understanding how changes in prey assemblages may affect predators, determining these components is inherently difficult in cryptic predators. The present study used animal-borne video data loggers to investigate the costs and benefits related to different prey types for female Australian fur seals (Arctocephalus pusillus doriferus), a primarily benthic foraging species in the low productivity Bass Strait, south-eastern Australia. A total of 1,263 prey captures, resulting from 2,027 prey detections, were observed in 84.5 h of video recordings from 23 individuals. Substantial differences in prey pursuit and handling times, gross energy gain and total energy expenditure were observed between prey types. Importantly, the profitability of prey was not significantly different between prey types, with the exception of elasmobranchs. This study highlights the benefit of animal-borne video data loggers for understanding the factors that influence foraging decisions in predators. Further studies incorporating search times for different prey types would further elucidate how profitability differs with prey type.

Geographic variation in at-sea movements, habitat use and diving behaviour of female Cape fur seals

2020 ◽  
Vol 649 ◽  
pp. 201-218
Author(s):  
JA Botha ◽  
SP Kirkman ◽  
JPY Arnould ◽  
AT Lombard ◽  
GJG Hofmeyr ◽  
...  
Keyword(s):  
Habitat Use ◽  
Prey Species ◽  
Dive Depth ◽  
Diving Behaviour ◽  
Foraging Strategies ◽  
Suitable Habitat ◽  
Vertical Movements ◽  
Marine Predator ◽  
Fur Seals ◽  
Shelf Slope

Knowledge of animal foraging behaviour has implications for management and conservation. While Cape fur seals Arctocephalus pusillus pusillus comprise a major proportion of the southern African marine predator biomass, little is known about their at-sea movements. We investigated foraging distribution, habitat use and diving behaviour for 35 adult female Cape fur seals from 3 breeding colonies experiencing contrasting oceanographic regimes. Animals from Black Rocks, the smallest and eastern-most colony, undertook shorter foraging trips and utilised shallower waters over the shelf. In comparison, animals from the larger west coast colonies, at Kleinsee and False Bay, travelled further and utilised deeper shelf and shelf-slope waters. However, across colonies, females typically preferred depths of <500 m and slopes of <5°. Kleinsee and False Bay seals selected sea surface temperatures within the range typically preferred by pelagic prey species such as round herring, sardine and anchovy (14-19°C). Black Rocks individuals showed bimodal preferences for colder (16°C) and warmer waters (>22°C). Dive behaviour was similar between Kleinsee and False Bay individuals (unavailable from Black Rocks), with both pelagic and benthic foraging evident. Diel patterns were apparent at both sites, as dive depth and benthic diving increased significantly during daylight hours, likely reflecting vertical movements of prey species. We provide the first assessment of Cape fur seal movement behaviour for the South African component of the population. Observed geographic differences likely reflect the availability of suitable habitat but may also indicate differences in foraging strategies and density-dependent effects throughout the range of this species.

scholarly journals Whisker isotopic signature depicts migration patterns and multi-year intra- and inter-individual foraging strategies in fur seals

2009 ◽  
Vol 5 (6) ◽  
pp. 830-832 ◽  
Author(s):  
Y. Cherel ◽  
L. Kernaléguen ◽  
P. Richard ◽  
C. Guinet
Keyword(s):  
Population Level ◽  
Isotopic Signature ◽  
Trophic Niche ◽  
Foraging Strategies ◽  
Individual Level ◽  
Dietary History ◽  
Isotopic Signatures ◽  
Fur Seals ◽  
The Individual ◽  
Antarctic Fur Seals

The movement and dietary history of individuals can be studied using stable isotope records in archival keratinous tissues. Here, we present a chronology of temporally fine-scale data on the trophic niche of otariid seals by measuring the isotopic signature of serially sampled whiskers. Whiskers of male Antarctic fur seals breeding at the Crozet Islands showed synchronous and regular oscillations in both their δ 13 C and δ 15 N values that are likely to represent their annual migrations over the long term (mean 4.8 years). At the population level, male Antarctic fur seals showed substantial variation in both δ 13 C and δ 15 N values, occupying nearly all the ‘isotopic space’ created by the diversity of potential oceanic habitats (from high Antarctica to the subtropics) and prey (from Antarctic krill to subantarctic and subtropical mesopelagic fishes). At the individual level, whisker isotopic signatures depict a large diversity of foraging strategies. Some seals remained in either subantarctic or Antarctic waters, while the migratory cycle of most animals encompassed a wide latitudinal gradient where they fed on different prey. The isotopic signature of whiskers, therefore, revealed new multi-year foraging strategies of male Antarctic fur seals and is a powerful tool for investigating the ecological niche during cryptic stages of mammals' life.

scholarly journals Mating success and body condition not related to foraging specializations in male fur seals

2016 ◽  
Vol 3 (7) ◽  
pp. 160143 ◽  
Author(s):  
L. Kernaléguen ◽  
Y. Cherel ◽  
C. Guinet ◽  
J. P. Y. Arnould
Keyword(s):  
Body Size ◽  
Mating Success ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Isotopic Niche ◽  
Fur Seals ◽  
Harem Size ◽  
Fitness Consequences ◽  
Feeding Habitat

Individual specialization is widespread among wild populations. While its fitness consequences are central in predicting the ecological and evolutionary trajectories of populations, they remain poorly understood. Long-term individual foraging specializations occur in male Antarctic ( Arctocephalus gazella ) and Australian ( A. pusillus doriferus ) fur seals. Strong selective pressure is expected in these highly dimorphic and polygynous species, raising the question of the fitness payoffs associated with different foraging strategies. We investigated the relationship between individual isotopic niche (a proxy of foraging specialization), body size and condition, and an index of reproductive success (harem size) in territorial males. Individuals varied greatly in their skin and fur isotopic values reflecting a range of foraging strategies within the two populations. However, in both species, isotopic niche was not correlated to body size, condition or mating success ( R 2 / ρ  < 0.06). Furthermore, no foraging niche was predominant in either species, which would have indicated a substantial long-term fitness benefit of a particular strategy via a higher survival rate. These results suggest that the fitness consequences of a foraging strategy depend not only on the quality of prey and feeding habitat but also on an individual's hunting efficiency and skills.

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