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Ouled-Cheikh J, March D, Borras-Chavez R, Drago M, Goebel ME, Fariña JM, Gazo M, Coll M, Cardona L. Future climate-induced distribution shifts in a sexually dimorphic key predator of the Southern Ocean. GLOBAL CHANGE BIOLOGY 2024; 30:e17191. [PMID: 38433338 DOI: 10.1111/gcb.17191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 12/20/2023] [Accepted: 12/21/2023] [Indexed: 03/05/2024]
Abstract
The response to climate change in highly dimorphic species can be hindered by differences between sexes in habitat preferences and movement patterns. The Antarctic fur seal, Arctocephalus gazella, is the most abundant pinniped in the Southern Hemisphere, and one of the main consumers of Antarctic krill, Euphausia superba, in the Southern Ocean. However, the populations breeding in the Atlantic Southern Ocean are decreasing, partly due to global warming. Male and female Antarctic fur seals differ greatly in body size and foraging ecology, and little is known about their sex-specific responses to climate change. We used satellite tracking data and Earth System Models to predict changes in habitat suitability for male and female Antarctic fur seals from the Western Antarctic Peninsula under different climate change scenarios. Under the most extreme scenario (SSP5-8.5; global average temperature +4.4°C projected by 2100), suitable habitat patches will shift southward during the non-breeding season, leading to a minor overall habitat loss. The impact will be more pronounced for females than for males. The reduction of winter foraging grounds might decrease the survival of post-weaned females, reducing recruitment and jeopardizing population viability. During the breeding season, when males fast on land, suitable foraging grounds for females off the South Shetland Islands will remain largely unmodified, and new ones will emerge in the Bellingshausen Sea. As Antarctic fur seals are income breeders, the foraging grounds of females should be reasonably close to the breeding colony. As a result, the new suitable foraging grounds will be useful for females only if nearby beaches currently covered by sea ice emerge by the end of the century. Furthermore, the colonization of these new, ice-free breeding locations might be limited by strong female philopatry. These results should be considered when managing the fisheries of Antarctic krill in the Southern Ocean.
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Affiliation(s)
- Jazel Ouled-Cheikh
- Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
- iMARES group, Departament de Recursos Marins Renovables, Institut de Ciències del Mar (ICM-CSIC), Barcelona, Spain
| | - David March
- Institut Cavanilles de Biodiversitat i Biologia Evolutiva (ICBiBE), Universitat de València, Paterna, València, Spain
- Centre for Ecology and Conservation, College of Life and Environmental Science, University of Exeter, Penryn, Cornwall, UK
| | - Renato Borras-Chavez
- Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Santiago, Chile
- Department of Biology, Baylor University, Waco, Texas, USA
| | - Massimiliano Drago
- Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - Michael E Goebel
- Institute of Marine Sciences, University of California Santa Cruz (UCSC), Santa Cruz, California, USA
- Antarctic Ecosystem Research Division, SWFSC, NMFS, NOAA, La Jolla, California, USA
| | - José M Fariña
- Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Manel Gazo
- Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - Marta Coll
- iMARES group, Departament de Recursos Marins Renovables, Institut de Ciències del Mar (ICM-CSIC), Barcelona, Spain
- Ecopath International Initiative (EII), Barcelona, Spain
| | - Luis Cardona
- Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
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2
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Lea M, Tainsh LW, Mattlin R, Torres L, Vinette Herrin K, Thompson DR, Hindell MA. The benthic-pelagic continuum: Age class and sex differences in the use of the vertical dimension by a rare pinniped. Ecol Evol 2023; 13:e10601. [PMID: 37928196 PMCID: PMC10622853 DOI: 10.1002/ece3.10601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 08/12/2023] [Accepted: 08/16/2023] [Indexed: 11/07/2023] Open
Abstract
Sea lions as a group, display strong site fidelity, and varying degrees of vulnerability to environmental change, disease and fisheries interactions. One of the rarest pinnipeds, the New Zealand sea lion (NZSL, Phocarctos hookeri) has a very restricted breeding range. At Campbell Island/Motu Ihupuku, one of the two primary breeding sites, at-sea foraging behaviour is unknown. We hypothesised that NZSL of various sex and age classes would utilise the water column differently due to differing physiological constraints and therefore have different accessibility to prey resources. We tested whether sea lion diving behaviour varied in relation to (i) age and sex class, (ii) time of day and (iii) water depth. We also hypothesised that the proportion of benthic/pelagic diving, and consequently risk of fisheries interaction, would vary in relation to age and sex. Satellite telemetry tags were deployed on 25 NZSL from a range of age/sex classes recording dive depth, duration and location. Adult females and juveniles used inshore, benthic habitats, while sub-adult males also utilised benthic habitats, they predominantly used pelagic habitat at greater distances from the island. Adult females and juveniles exhibited shorter dives than the same age/sex classes at the Auckland Islands, suggesting a lower dive effort for these age/sex classes at Campbell Island/Motu Ihupuku. Adult females dived more frequently than other age/sex classes, likely operating closer to their physiological limits; however, further data for this age class is needed. Sub-adult male use of pelagic prey may increase their exposure to mid-water trawls; however, further research detailing the degree of spatial overlap with fisheries is required. This study highlights the utility of spatially explicit dive data to predict vertical habitat use, niche separation of various age and sex classes of marine predators and attribute potential fisheries interaction risk in relation to predator habitat use.
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Affiliation(s)
- Mary‐Anne Lea
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
| | - Lachlan W. Tainsh
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
| | - Rob Mattlin
- Marine Wildlife Research, LtdNelsonNew Zealand
| | - Leigh Torres
- Department of Fisheries and Wildlife, Marine Mammal Institute, Hatfield Marine Science CenterOregon State UniversityNewportOregonUSA
| | | | | | - Mark A. Hindell
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
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March D, Drago M, Gazo M, Parga M, Rita D, Cardona L. Winter distribution of juvenile and sub-adult male Antarctic fur seals (Arctocephalus gazella) along the western Antarctic Peninsula. Sci Rep 2021; 11:22234. [PMID: 34782702 PMCID: PMC8593074 DOI: 10.1038/s41598-021-01700-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 11/02/2021] [Indexed: 12/02/2022] Open
Abstract
Detailed knowledge of habitat use by marine megafauna is critical to understand their ecological roles and for the adequate management of marine resources. Antarctic fur seals (Arctocephalus gazella) inhabiting the Atlantic sector of the Southern Ocean prey largely on Antarctic krill (Euphausia superba) and play a central role in managing the krill fishery. Here, we assessed the demographic structure of three post-mating, early moult male haul-outs in the South Shetland Islands in early March and calculated the relative contribution of juveniles (1–4 years old) and sub-adult males (5–6 years) to the population remaining in maritime Antarctica after the breeding season. We also satellite tagged 11 juvenile males and four sub-adult males to analyze their movements and develop a species distribution model including both age classes. Our results highlighted the dominance of young individuals in the male population, revealed that they do not behave as central place foragers and identified key environmental drivers that affected their distribution at-sea throughout winter. Predicted potential foraging habitat overlapped highly with the known distribution of Antarctic krill, and identified the waters off the western Antarctic Peninsula and the Scotia Sea as the core of the distribution area of juvenile and sub-adult male Antarctic fur seals in winter. This pattern is similar to that of adult males but totally different from that of adult females, as the latter overwinter in areas at latitude 45–55° S. This segregation has implications for the ecology and management of the krill fishery.
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Affiliation(s)
- David March
- IRBio and Department of Evolutionary Biology, Ecology and Environmental Science, Faculty of Biology, University of Barcelona, Avinguda Diagonal 643, 08028, Barcelona, Spain. .,Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, TR10 9FE, UK.
| | - Massimiliano Drago
- IRBio and Department of Evolutionary Biology, Ecology and Environmental Science, Faculty of Biology, University of Barcelona, Avinguda Diagonal 643, 08028, Barcelona, Spain
| | - Manel Gazo
- IRBio and Department of Evolutionary Biology, Ecology and Environmental Science, Faculty of Biology, University of Barcelona, Avinguda Diagonal 643, 08028, Barcelona, Spain
| | - Mariluz Parga
- SUBMON - Marine Environmental Services, Ortigosa 14, 08003, Barcelona, Spain
| | - Diego Rita
- IRBio and Department of Evolutionary Biology, Ecology and Environmental Science, Faculty of Biology, University of Barcelona, Avinguda Diagonal 643, 08028, Barcelona, Spain
| | - Luis Cardona
- IRBio and Department of Evolutionary Biology, Ecology and Environmental Science, Faculty of Biology, University of Barcelona, Avinguda Diagonal 643, 08028, Barcelona, Spain
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4
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Nagel R, Mews S, Adam T, Stainfield C, Fox-Clarke C, Toscani C, Langrock R, Forcada J, Hoffman JI. Movement patterns and activity levels are shaped by the neonatal environment in Antarctic fur seal pups. Sci Rep 2021; 11:14323. [PMID: 34253749 PMCID: PMC8275608 DOI: 10.1038/s41598-021-93253-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 06/04/2021] [Indexed: 02/06/2023] Open
Abstract
Tracking studies of juveniles are rare compared to those of adults, and consequently little is known about the influence of intrinsic and extrinsic factors on activity during this critical life stage. We used hourly GPS data, collected from 66 Antarctic fur seal pups from birth until moulting, to investigate the explanatory power of multiple individual-based and environmental variables on activity levels. Pups were sampled from two nearby breeding colonies of contrasting density during two subsequent years, and a two-state hidden Markov model was used to identify modalities in their movement behaviour, specifically 'active' and 'inactive' states. We found that movement was typified by central place exploration, with active movement away from and subsequent return to a location of inactivity. The probability of such directed exploration was unaffected by several factors known to influence marine mammal movement including sex, body condition, and temperature. Compared to pups born at the high-density colony, pups at low-density were more active, increased their activity with age, and transitioned earlier into the tussock grass, which offers protection from predators and extreme weather. Our study illustrates the importance of extrinsic factors, such as colony of birth, to early-life activity patterns and highlights the adaptive potential of movement.
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Affiliation(s)
- Rebecca Nagel
- grid.7491.b0000 0001 0944 9128Department of Animal Behaviour, Bielefeld University, 33501 Bielefeld, Germany
| | - Sina Mews
- grid.7491.b0000 0001 0944 9128Department of Business Administration and Economics, Bielefeld University, 33501 Bielefeld, Germany
| | - Timo Adam
- grid.7491.b0000 0001 0944 9128Department of Business Administration and Economics, Bielefeld University, 33501 Bielefeld, Germany ,grid.11914.3c0000 0001 0721 1626Centre for Research into Ecological and Environmental Modelling, School of Mathematics and Statistics, The Observatory, Buchanan Gardens, University of St Andrews, St Andrews, KY16 9LZ UK
| | - Claire Stainfield
- grid.478592.50000 0004 0598 3800British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET UK
| | - Cameron Fox-Clarke
- grid.478592.50000 0004 0598 3800British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET UK
| | - Camille Toscani
- grid.478592.50000 0004 0598 3800British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET UK
| | - Roland Langrock
- grid.7491.b0000 0001 0944 9128Department of Business Administration and Economics, Bielefeld University, 33501 Bielefeld, Germany
| | - Jaume Forcada
- grid.478592.50000 0004 0598 3800British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET UK
| | - Joseph I. Hoffman
- grid.7491.b0000 0001 0944 9128Department of Animal Behaviour, Bielefeld University, 33501 Bielefeld, Germany ,grid.478592.50000 0004 0598 3800British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET UK
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5
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Orgeret F, Reisinger RR, Carpenter-Kling T, Keys DZ, Corbeau A, Bost CA, Weimerskirch H, Pistorius PA. Spatial segregation in a sexually dimorphic central place forager: Competitive exclusion or niche divergence? J Anim Ecol 2021; 90:2404-2420. [PMID: 34091891 DOI: 10.1111/1365-2656.13552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 05/29/2021] [Indexed: 12/11/2022]
Abstract
Sexual competition is increasingly recognized as an important selective pressure driving species distributions. However, few studies have investigated the relative importance of interpopulation versus intrapopulation competition in relation to habitat availability and selection. To explain spatial segregation between sexes that often occurs in non-territorial and central place foragers, such as seabirds, two hypotheses are commonly used. The 'competitive exclusion' hypothesis states that dominant individuals should exclude subordinate individuals through direct competition, whereas the 'niche divergence' hypothesis states that segregation occurs due to past competition and habitat specialization. We tested these hypotheses in two populations of an extreme wide-ranging and sexually dimorphic seabird, investigating the relative role of intrapopulation and interpopulation competition in influencing sex-specific distribution and habitat preferences. Using GPS loggers, we tracked 192 wandering albatrosses Diomedea exulans during four consecutive years (2016-2019), from two neighbouring populations in the Southern Ocean (Prince Edward and Crozet archipelagos). We simulated pseudo-tracks to create a null spatial distribution and used Kernel Density Estimates (KDE) and Resource Selection Functions (RSF) to distinguish the relative importance of within- versus between-population competition. Kernel Density Estimates showed that only intrapopulation sexual segregation was significant for each monitoring year, and that tracks between the two colonies resulted in greater overlap than expected from the null distribution, especially for the females. RSF confirmed these results and highlighted key at-sea foraging areas, even if the estimated of at-sea densities were extremely low. These differences in selected areas between sites and sexes were, however, associated with high interannual variability in habitat preferences, with no clear specific preferences per site and sex. Our results suggest that even with low at-sea population densities, historic intrapopulation competition in wide-ranging seabirds may have led to sexual dimorphism and niche specialization, favouring the 'niche divergence' hypothesis. In this study, we provide a protocol to study competition within as well as between populations of central place foragers. This is relevant for understanding their distribution patterns and population regulation, which could potentially improve management of threatened populations.
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Affiliation(s)
- Florian Orgeret
- Marine Apex Predator Research Unit (MAPRU), Department of Zoology, Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth, South Africa
| | - Ryan R Reisinger
- Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Tegan Carpenter-Kling
- Marine Apex Predator Research Unit (MAPRU), Department of Zoology, Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth, South Africa.,DST-NRF Centre of Excellence at the FitzPatrick, Institute of African Ornithology, Nelson Mandela University, Port Elizabeth, South Africa
| | - Danielle Z Keys
- Marine Apex Predator Research Unit (MAPRU), Department of Zoology, Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth, South Africa
| | - Alexandre Corbeau
- Centre d'Etudes Biologiques de Chizé, UMR 7372 du CNRS-Université de La Rochelle, Villiers-en-Bois, France
| | - Charles-André Bost
- Centre d'Etudes Biologiques de Chizé, UMR 7372 du CNRS-Université de La Rochelle, Villiers-en-Bois, France
| | - Henri Weimerskirch
- Centre d'Etudes Biologiques de Chizé, UMR 7372 du CNRS-Université de La Rochelle, Villiers-en-Bois, France
| | - Pierre A Pistorius
- Marine Apex Predator Research Unit (MAPRU), Department of Zoology, Institute for Coastal and Marine Research, Nelson Mandela University, Port Elizabeth, South Africa.,DST-NRF Centre of Excellence at the FitzPatrick, Institute of African Ornithology, Nelson Mandela University, Port Elizabeth, South Africa
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6
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Application of Combined Analyses of Stable Isotopes and Stomach Contents for Understanding Ontogenetic Niche Shifts in Silver Croaker ( Pennahia argentata). INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18084073. [PMID: 33924310 PMCID: PMC8070473 DOI: 10.3390/ijerph18084073] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 04/05/2021] [Accepted: 04/08/2021] [Indexed: 11/17/2022]
Abstract
Stable isotope analysis (SIA) and stomach content analysis (SCA) were conducted to understand ontogenetic niche shifts in silver croaker Pennahia argentata inhabiting the southern coastal waters of the Korean peninsula. Sampled P. argentata were classified into three groups based on their total length (TL; 60-80 mm TL, 80-120 mm TL, and 120-210 mm TL). Carbon isotope (δ13C) ratios were distinguishable, whereas nitrogen isotope (δ15N) ratios were not significantly different among size classes, and Standard Ellipse Area (SEA), estimated by δ13C and δ15N, was expanded with increasing TL from 0.2 ‰2 (60-80 mm TL) to 2.0 ‰2 (120-210 mm TL). SCA results showed variable contribution of dietary items to each size class. In particular, higher dietary contribution of Polychaeta to P. argentata of 80-120 mm TL than 120-210 mm TL mirrored variation in δ13C values of P. argentata in those size classes. Based on the combined analyses involving SIA and SCA, we concluded that P. argentata underwent ontogenetic niche shifts, particularly dietary shifts, with growth stages. Ontogenetic niche shifting is a representative survival strategy in fish, and, therefore, represents essential information for managing fisheries. The present study demonstrated applicability of combined SIA and SCA analyses, not only for dietary resource tracing, but also for ecological niche studies.
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Jones KA, Wood H, Ashburner JP, Forcada J, Ratcliffe N, Votier SC, Staniland IJ. Risk exposure trade-offs in the ontogeny of sexual segregation in Antarctic fur seal pups. Behav Ecol 2020; 31:719-730. [PMID: 32595270 PMCID: PMC7303822 DOI: 10.1093/beheco/araa018] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 01/31/2020] [Accepted: 02/26/2020] [Indexed: 11/21/2022] Open
Abstract
Sexual segregation has important ecological implications, but its initial development in early life stages is poorly understood. We investigated the roles of size dimorphism, social behavior, and predation risk on the ontogeny of sexual segregation in Antarctic fur seal, Arctocephalus gazella, pups at South Georgia. Beaches and water provide opportunities for pup social interaction and learning (through play and swimming) but increased risk of injury and death (from other seals, predatory birds, and harsh weather), whereas tussock grass provides shelter from these risks but less developmental opportunities. One hundred pups were sexed and weighed, 50 on the beach and 50 in tussock grass, in January, February, and March annually from 1989 to 2018. Additionally, 19 male and 16 female pups were GPS-tracked during lactation from December 2012. Analysis of pup counts and habitat use of GPS-tracked pups suggested that females had a slightly higher association with tussock grass habitats and males with beach habitats. GPS-tracked pups traveled progressively further at sea as they developed, and males traveled further than females toward the end of lactation. These sex differences may reflect contrasting drivers of pup behavior: males being more risk prone to gain social skills and lean muscle mass and females being more risk averse to improve chances of survival, ultimately driven by their different reproductive roles. We conclude that sex differences in habitat use can develop in a highly polygynous species prior to the onset of major sexual size dimorphism, which hints that these sex differences will increasingly diverge in later life.
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Affiliation(s)
- Kayleigh A Jones
- Ecosystems Team, British Antarctic Survey, High Cross, Madingley road, Cambridge, UK
- College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, UK
| | - Hannah Wood
- Ecosystems Team, British Antarctic Survey, High Cross, Madingley road, Cambridge, UK
| | - Jonathan P Ashburner
- Ecosystems Team, British Antarctic Survey, High Cross, Madingley road, Cambridge, UK
| | - Jaume Forcada
- Ecosystems Team, British Antarctic Survey, High Cross, Madingley road, Cambridge, UK
| | - Norman Ratcliffe
- Ecosystems Team, British Antarctic Survey, High Cross, Madingley road, Cambridge, UK
| | - Stephen C Votier
- College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, UK
| | - Iain J Staniland
- Ecosystems Team, British Antarctic Survey, High Cross, Madingley road, Cambridge, UK
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8
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Jones KA, Ratcliffe N, Votier SC, Newton J, Forcada J, Dickens J, Stowasser G, Staniland IJ. Intra-specific Niche Partitioning in Antarctic Fur Seals, Arctocephalus gazella. Sci Rep 2020; 10:3238. [PMID: 32094418 PMCID: PMC7039921 DOI: 10.1038/s41598-020-59992-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 01/31/2020] [Indexed: 11/10/2022] Open
Abstract
Competition for resources within a population can lead to niche partitioning between sexes, throughout ontogeny and among individuals, allowing con-specifics to co-exist. We aimed to quantify such partitioning in Antarctic fur seals, Arctocephalus gazella, breeding at South Georgia, which hosts ~95% of the world’s population. Whiskers were collected from 20 adult males and 20 adult females and stable isotope ratios were quantified every 5 mm along the length of each whisker. Nitrogen isotope ratios (δ15N) were used as proxies for trophic position and carbon isotope ratios (δ13C) indicated foraging habitat. Sexual segregation was evident: δ13C values were significantly lower in males than females, indicating males spent more time foraging south of the Polar Front in maritime Antarctica. In males δ13C values declined with age, suggesting males spent more time foraging south throughout ontogeny. In females δ13C values revealed two main foraging strategies: 70% of females spent most time foraging south of the Polar Front and had similar δ15N values to males, while 30% of females spent most time foraging north of the Polar Front and had significantly higher δ15N values. This niche partitioning may relax competition and ultimately elevate population carrying capacity with implications for ecology, evolution and conservation.
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Affiliation(s)
| | | | | | - Jason Newton
- Scottish Universities Environmental Research Centre, East Kilbride, Scotland
| | | | - John Dickens
- British Antarctic Survey, Cambridge, United Kingdom
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9
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Migratory strategies of juvenile northern fur seals (Callorhinus ursinus): bridging the gap between pups and adults. Sci Rep 2019; 9:13921. [PMID: 31558737 PMCID: PMC6763446 DOI: 10.1038/s41598-019-50230-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 09/02/2019] [Indexed: 11/08/2022] Open
Abstract
In species exhibiting differential migration by sex and age, understanding what differences exist, and the adaptive reasons for these differences is critical for determining how demographic groups will respond to environmental variability and anthropogenic perturbations. We used satellite-telemetered movement and diving data to investigate differential migration and its ontogeny in a highly migratory North Pacific Ocean predator, the northern fur seal (Callorhinus ursinus; NFS), with a focus on understudied juvenile (1- to 2-year-old) animals. We instrumented 71 juvenile NFS in two years (2006-07 and 2007-08) at three major North American breeding sites and compared their migratory strategies with pups and adults. Although sexual dimorphism is strong in adult NFS, only weak differences in body mass between sexes were found in juveniles, which had similar body mass to pups (~3-4 months). However, unlike widely-dispersed pups, juvenile male and female NFS dispersed in different directions, and used different habitats characterized by distinct hydrography and prey assemblages during migration, similar to breeding adults. Juvenile diving behavior differed only modestly among habitats and between sexes, consistent with weak differences in body mass. Evidence of habitat sexual segregation by juvenile NFS contradicts previous hypotheses that physiological differences predominantly drive the ontogeny of differential migration.
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10
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Pagani-Núñez E, Barnett CRA, Senar JC. Age and sex differences in niche use at molt and its effect on plumage coloration characteristics in a bird. Curr Zool 2018; 65:251-260. [PMID: 31263483 PMCID: PMC6595419 DOI: 10.1093/cz/zoy062] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 07/17/2018] [Indexed: 01/16/2023] Open
Abstract
Bird plumage is often very colorful and can communicate the quality of the bearer to conspecifics. These plumage-based signals of quality are composed of multiple pigments (e.g., melanin and carotenoids). Therefore, sex and age classes, which often show marked differences in plumage coloration, may have different dietary needs for the different plumage components and this might promote preferences for different dietary niches at different molting stages. However, no study has addressed the role that changes in niche use play in the expression of multiple component plumage signals in birds. We used stable isotope analysis to test the hypothesis that niche use is related to age and sex and to differently cultured plumage patches, yellow carotenoid-based and black melanin-based, in great tits Parus major. We recorded high niche overlap between plumage patches, although δ15N was higher in black than yellow plumage. Niche overlap was relatively low for age classes and relatively high for sex classes, and age classes showed a contrasting pattern of niche overlap between carotenoid- and melanin-based plumages. Moreover, δ13C, but not δ15N, had a significant negative relationship with carotenoid-based plumage, which was only apparent in juveniles. Taken together, our results demonstrate that niche use had a moderate influence on plumage coloration characteristics of great tit individuals, mostly associated with δ13C rather than with δ15N and with age rather than with sex. Therefore, our study is significant because it confirms the relevance of niche use during ornament production in free-living birds.
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Affiliation(s)
- Emilio Pagani-Núñez
- State Key Laboratory of Biocontrol, Department of Ecology/School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Craig R A Barnett
- Department of Zoology, Graduate School of Science, University of Kyoto, Kitashirakawa-oiwake-cho, Sakio-ku, Kyoto, Japan
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11
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Cherel Y, Parenteau C, Bustamante P, Bost C. Stable isotopes document the winter foraging ecology of king penguins and highlight connectivity between subantarctic and Antarctic ecosystems. Ecol Evol 2018; 8:2752-2765. [PMID: 29531692 PMCID: PMC5838085 DOI: 10.1002/ece3.3883] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 12/11/2017] [Accepted: 01/02/2018] [Indexed: 11/30/2022] Open
Abstract
The poorly known winter foraging ecology of the king penguin, a major Southern Ocean consumer, was investigated at the subantarctic Crozet Islands where the largest global population breeds. Blood δ13C and δ15N values were used as proxies of the birds' foraging habitat and diet, respectively, and circulating prolactin levels helped in determining the birds' reproductive status. Plasma prolactin concentrations showed that king penguin adults of unknown breeding status (n = 52) that were present at the colony in winter were in fact breeders and failed breeders, but were not non -breeders. Circulating prolactin was neither related to δ13C nor δ15N values, thus suggesting that both breeders and failed breeders used the same foraging habitats and fed on the same prey. Plasma and blood cell isotopic values depicted four new relevant biological features on the feeding strategies of king penguins during the critical winter period: (1) 42% of the birds foraged in the distant Antarctic Zone, but 58% fed primarily in subantarctic waters (δ13C), (2) they preyed upon myctophids in both zones (δ15N), (3) individuals were consistent in their foraging strategies over the winter months (δ13C and δ15N), and (4) a higher proportion of females (77%-80%) than males (27%-31%) favored feeding in distant Antarctic waters (δ13C). This study highlights trophic connectivity between subantarctic and Antarctic ecosystems and hence the key role of energy export from Antarctic waters to sustain breeding populations of subantarctic predators, including during the Austral winter.
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Affiliation(s)
- Yves Cherel
- Centre d'Etudes Biologiques de Chizé (CEBC)UMR 7372 du CNRS‐Université de La RochelleVilliers‐en‐BoisFrance
| | - Charline Parenteau
- Centre d'Etudes Biologiques de Chizé (CEBC)UMR 7372 du CNRS‐Université de La RochelleVilliers‐en‐BoisFrance
| | - Paco Bustamante
- Littoral, Environnement et Sociétés (LIENSs)UMR 7266 du CNRS‐Université de la RochelleLa RochelleFrance
| | - Charles‐André Bost
- Centre d'Etudes Biologiques de Chizé (CEBC)UMR 7372 du CNRS‐Université de La RochelleVilliers‐en‐BoisFrance
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