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.

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 Artificial size selection experiment reveals telomere length dynamics and fitness consequences in a wild passerine

2021 ◽  
Author(s):  
Michael Pepke ◽  
Thomas Kvalnes ◽  
Bernt Rønning ◽  
Henrik Jensen ◽  
Winnie Boner ◽  
...  
Keyword(s):  
Body Size ◽  
Telomere Length ◽  
Early Life ◽  
Bird Species ◽  
Disruptive Selection ◽  
Size Selection ◽  
Trade Offs ◽  
Fitness Consequences ◽  
Selection For

Changes in telomere dynamics could underlie life-history trade-offs among growth, size and longevity, but our ability to quantify such mechanistic processes in natural, unmanipulated populations is limited. We investigated how 4 years of artificial selection for either larger or smaller body size affected early-life telomere length in two insular populations of wild house sparrows. A negative correlation between telomere length and structural size was evident under both selection regimes. The study also revealed that male sparrows had longer telomeres than females, after controlling for size, and there was a significant negative effect of harsh weather conditions on telomere length. The long-term fitness consequences of these changes in early-life telomere length induced by the artificial size selection were explored over a period of 11 years. These analyses indicated disruptive selection on telomere length because both short and long early-life telomere length tended to be associated with the lowest mortality rates and highest life expectancy. There was also weak evidence for a negative association between telomere length and annual reproductive success, but only in the population where body size was increased experimentally. Our results suggest that natural selection for optimal body size in wild animals will affect early-life telomere length during growth, which is known to be linked to longevity in birds, but also that the importance of telomeres for long-term somatic maintenance and fitness is complex in a wild bird species.

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

Seasonal differences in foraging and isotopic niche width related to body size in Gulf of Alaska harbor seals

2019 ◽  
Vol 97 (12) ◽  
pp. 1156-1163 ◽  
Author(s):  
Justin Smith ◽  
Shawna Karpovich ◽  
Lara Horstmann ◽  
Julie McIntyre ◽  
Diane M. O’Brien
Keyword(s):  
Body Size ◽  
Stable Isotope ◽  
Isotope Analysis ◽  
Isotope Ratios ◽  
Gulf Of Alaska ◽  
Harbor Seal ◽  
Foraging Strategies ◽  
Stable Isotope Ratios ◽  
Isotopic Niche ◽  
Harbor Seals

Harbor seals (Phoca vitulina Linnaeus, 1758) use different foraging strategies based on body size and sex, but this difference can be difficult to evaluate across seasons. We used stable isotope analysis of harbor seal whiskers from 32 individuals to assess seasonal foraging of seals inhabiting tidewater glacial habitat in Southeast Alaska. We analyzed stable isotope ratios from serial sections of whiskers, estimated deposition date for each section, and used mixed models to determine if sex and body size influence stable isotope ratios. Seals were grouped by size (>1.4 m or ≤1.4 m curvilinear length) as a proxy for sexual maturity to describe isotopic differences between groups using standard ellipse corrected area. Mean carbon and nitrogen isotope ratios differed significantly between size classes (p < 0.005), with no effect of sex. Larger seals exhibited a broader isotopic niche in the fall, winter, and spring relative to smaller seals, but not in the summer. Our results suggest that seals using tidewater glacial habitat share common foraging behavior in the summer, while larger seals exhibit more diverse foraging throughout the rest of the year. These results highlight the importance of tidewater glacial habitat for this population of harbor seals during the summer.

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 The isotopic niche of Atlantic, biting marine mammals and its relationship to skull morphology and body size

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Massimiliano Drago ◽  
Marco Signaroli ◽  
Meica Valdivia ◽  
Enrique M. González ◽  
Asunción Borrell ◽  
...  
Keyword(s):  
Body Size ◽  
Atlantic Ocean ◽  
Fisheries Management ◽  
Marine Mammals ◽  
Trophic Position ◽  
Sympatric Species ◽  
Isotopic Niche ◽  
Apex Predators ◽  
Skull Morphology ◽  
Ecosystem Based Fisheries Management

AbstractUnderstanding the trophic niches of marine apex predators is necessary to understand interactions between species and to achieve sustainable, ecosystem-based fisheries management. Here, we review the stable carbon and nitrogen isotope ratios for biting marine mammals inhabiting the Atlantic Ocean to test the hypothesis that the relative position of each species within the isospace is rather invariant and that common and predictable patterns of resource partitioning exists because of constrains imposed by body size and skull morphology. Furthermore, we analyze in detail two species-rich communities to test the hypotheses that marine mammals are gape limited and that trophic position increases with gape size. The isotopic niches of species were highly consistent across regions and the topology of the community within the isospace was well conserved across the Atlantic Ocean. Furthermore, pinnipeds exhibited a much lower diversity of isotopic niches than odontocetes. Results also revealed body size as a poor predictor of the isotopic niche, a modest role of skull morphology in determining it, no evidence of gape limitation and little overlap in the isotopic niche of sympatric species. The overall evidence suggests limited trophic flexibility for most species and low ecological redundancy, which should be considered for ecosystem-based fisheries management.

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.

Multiple Fertilization and Consecutive Spawning in Large American Lobsters, Homarus americanus

1986 ◽  
Vol 43 (11) ◽  
pp. 2291-2294 ◽  
Author(s):  
S. L. Waddy ◽  
D. E. Aiken
Keyword(s):  
Body Size ◽  
Carapace Length ◽  
Homarus Americanus ◽  
Large Female ◽  
Bay Of Fundy ◽  
Relative Fecundity ◽  
Logarithmic Relationship

Large female American lobsters, Homarus americanus (> 120 mm carapace length), maintained at nearshore Bay of Fundy temperatures often spawn twice without an intervening molt (consecutive spawning). Consecutive spawning occurs in two forms: successive-year (spawning in two successive summers, a molt in the first and fourth years) and alternate-year (spawning in alternate summers, a molt in the first and fifth years). In both types, females often are able to fertilize the two successive broods with the sperm from a single insemination (multiple fertilization). Twenty of 21 large females that were held for up to 13 yr displayed one of these types of consecutive spawning. Consecutive spawning and multiple fertilization enable large lobsters to spawn more frequently over the long term than their smaller counterparts. This, combined with the logarithmic relationship between body size and numbers of eggs produced, means that very large lobsters have a much greater relative fecundity than previously thought.

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