Segregation of diets by sex and individual in South American fur seals

Lima, Renan C. de; Franco‐Trecu, Valentina; Carrasco, Thayara S.; Inchausti, Pablo; Secchi, Eduardo R.; Botta, Silvina

doi:10.1007/s10452-021-09915-9

Cited by 5 publications

(7 citation statements)

References 75 publications

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“…4; Saporiti et al 2016;Drago et al 2017). This is consistent with the prevalence of pelagic and demersal-pelagic fishes and squids in the diet of fur seals (Naya et al 2002;Franco-Trecu et al 2014;de Lima et al 2022), compared to the prevalence of benthic prey in the diet of sea lions throughout the year, although they increase the consumption of more pelagic prey during the pre-breeding season (Franco-Trecu et al 2014;Drago et al 2015). The different trophic positions of the two otariid species is further supported by the higher δ 15 N values of sea lions (Drago et al 2021).…”

Section: Origin Of Resources According To δ 34 S δ 18 O δ 13 C and δ ...supporting

confidence: 73%

“…The differences between females and males for both otariid species (South American sea lions and fur seals) were consistent with their sexual dimorphism and distinct behavior (Cárdenas-Alayza 2018a, b). In both cases, females usually stay closer to the coast and near to their breeding grounds (Rodríguez et al 2013;González Carman et al 2016), whereas males often perform long-distance foraging trips further from their rookeries and reach more marine waters with less terrestrial influence (Giardino et al 2016;de Lima et al 2022), as evidenced here by the higher δ 34 S values found in males (Connolly et al 2004). Nonetheless, the low δ 18 O values (Fig.…”

Section: Origin Of Resources According To δ 34 S δ 18 O δ 13 C and δ ...mentioning

confidence: 79%

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Niche Partitioning Among Marine Mammals Inhabiting a Large Estuary as Revealed by Stable Isotopes of C, N, S, and O

Cani

Cardona

Valdivia³

et al. 2023

Estuaries and Coasts

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Detailed knowledge on habitat use by marine mammals is critical to understand their role in the ecosystem. The stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) have been widely used to study the trophic ecology of marine mammals, but the stable isotope ratios of other elements such as sulfur (δ34S) and oxygen (δ18O) can better inform about habitat use in areas with strong salinity and redox gradients. The Río de la Plata estuary represents the largest freshwater runoff in the south-western Atlantic Ocean and supports a rich community of marine mammals. Here, we analyzed δ34S values in bone from seven marine mammal species inhabiting the estuary and the adjacent Atlantic Ocean, in order to complement previous isotopic data (δ13C, δ15N and δ18O) and compare their resolution as habitat tracers. As expected, δ34S and δ18O offered relevant insights into the characterization of the habitat used by marine mammals and allowed a better delineation of habitat partitioning between them. Bottlenose dolphins, South American sea lions and South American fur seals seem to be frequent users of the less saline areas of the estuary, whereas Burmeister´s porpoises, franciscana dolphins and false killer whales seemed to prefer the saltier marine waters close to the bottom. Fraser´s dolphins were the only inhabitants of true offshore waters. Our findings demonstrate how the integration of different stable isotope ratios can help disentangle fine habitat partitioning between marine mammals living in a complex ecosystem such as Río de la Plata.

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Section: Origin Of Resources According To δ 34 S δ 18 O δ 13 C and δ ...supporting

confidence: 73%

Section: Origin Of Resources According To δ 34 S δ 18 O δ 13 C and δ ...mentioning

confidence: 79%

Niche Partitioning Among Marine Mammals Inhabiting a Large Estuary as Revealed by Stable Isotopes of C, N, S, and O

Cani

Cardona

Valdivia³

et al. 2023

Estuaries and Coasts

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“…Male and female pinnipeds differ in their reproductive behaviour, which could affect trophic habits in the sexes (i.e. Drago et al 2015, Lima et al 2021). Specifically, males do not experience limitations associated with rearing pups, and hence, after a short reproductive period, they are free to use feeding areas that are far from the reproductive colonies.…”

Section: Discussionmentioning

confidence: 99%

Testing the niche variation hypothesis in pinnipeds

et al. 2022

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Individual trophic specialisation (ITS) has many important consequences for ecological and evolutionary processes. An old hypothesis highlighting the relevance of ITS is the niche variation hypothesis (NVH), which proposes that populations composed of trophically specialised individuals have a wider population niche than populations composed of more generalist individuals. Pinnipeds are a good model to test the NVH because they are mostly generalist species, living in dense colonies, and exhibiting variation in trophic niche width among populations. We tested the NVH in pinnipeds using longitudinal isotopic data: published δ13C and δ15N data obtained from sequential sections of whiskers (vibrissae) from individuals belonging to 14 populations. To the best of our knowledge, this is the first study evaluating the NVH by using longitudinal isotopic data. We compiled studies that published raw data on δ13C and δ15N for pinniped whisker segments to estimate the within‐individual and the between‐individuals components of variance, the total niche width (TNW), and ITS. One‐dimensional (i.e. δ13C or δ15N) and multi‐dimensional (i.e. δ13C and δ15N) analyses were used. Also, we tested whether an evolutionary component would affect the degree of ITS among pinniped species with different levels of shared ancestry. Our results indicate that, in line with the NVH, pinniped populations composed of more specialised individuals tend to show wider trophic niches. When analysing each sex separately, the hypothesis is supported for females but not for males. We believe that physiological and behavioural differences between sexes may explain this result. In females, high TNW is mainly related to greater differentiation among individuals, while in males, it is mainly related to high diversity of resources consumed by all individuals.

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“…Even as newborns or juveniles, males exhibit faster growth rates and achieve larger body sizes compared to females (Cappozzo et al, 1991). Consequently, otariid sexes often segregate in their resource use (e.g., Drago et al, 2015;Hobson et al, 1997;Kernaléguen et al, 2015), which can be advantageous in reducing intraspecific competition (Albernaz et al, 2017;de Lima et al, 2019de Lima et al, , 2022.…”

Section: Introductionmentioning

confidence: 99%

“…However, there is limited documentation of the feeding habits of these predators after weaning and during postreproductive dispersion. Consequently, their roles as seasonal components of alternative food webs are not well understood (Franco‐Trecu et al, 2012; de Lima et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Feeding habits of South American and sub‐Antarctic fur seals during their nonbreeding season in the southwestern Atlantic Ocean

Lima

Albernaz

Secchi

et al. 2023

Marine Mammal Science

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Stomach contents of South American (Arctocephalus australis) (n = 219) (SAFS) and sub‐Antarctic (A. tropicalis) (n = 37) (SFS) fur seals were opportunistically sampled from 1980 to 2021 to examine their feeding habits and resource partitioning in southern Brazil while in their nonreproductive periods. SAFSs mainly consumed abundant coastal pelagic species, such as Anchoa marinii and Doryteuthis sanpaulensis, resulting in high sexual trophic niche overlap. The frequency of occurrence (%FO) of fish prey, especially the overexploited Micropogonias furnieri, decreased between 1980–1992 and 2007–2021, while squid increased. For SFSs, offshore squids such as Ommastrephes bartramii and Illex argentinus were the most important prey considering both sexes in the long‐term. The interspecific trophic niche overlap was low, but it is likely underestimated since it increased with the inclusion of scat samples from SFSs. This sample‐size effect was also observed in Shannon's diversity index, which was lower for underrepresented SFSs. Marine debris ingestion was detected in both species (SAFS %FO = 2.7; SFS %FO = 8.3), with only flexible plastic material found. This study brings novel information on feeding habits of fur seal species in the extreme south of Brazil, as well as unprecedented information about their ecology during the nonreproductive period.

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Segregation of diets by sex and individual in South American fur seals

Cited by 5 publications

References 75 publications

Niche Partitioning Among Marine Mammals Inhabiting a Large Estuary as Revealed by Stable Isotopes of C, N, S, and O

Niche Partitioning Among Marine Mammals Inhabiting a Large Estuary as Revealed by Stable Isotopes of C, N, S, and O

Testing the niche variation hypothesis in pinnipeds

Feeding habits of South American and sub‐Antarctic fur seals during their nonbreeding season in the southwestern Atlantic Ocean

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