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Christian M, Oosthuizen WC, Bester MN, de Bruyn PJN. Robustly estimating the demographic contribution of immigration: Simulation, sensitivity analysis and seals. J Anim Ecol 2024; 93:632-645. [PMID: 38297453 DOI: 10.1111/1365-2656.14053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 01/11/2024] [Indexed: 02/02/2024]
Abstract
Identifying important demographic drivers of population dynamics is fundamental for understanding life-history evolution and implementing effective conservation measures. Integrated population models (IPMs) coupled with transient life table response experiments (tLTREs) allow ecologists to quantify the contributions of demographic parameters to observed population change. While IPMs can estimate parameters that are not estimable using any data source alone, for example, immigration, the estimated contribution of such parameters to population change is prone to bias. Currently, it is unclear when robust conclusions can be drawn from them. We sought to understand the drivers of a rebounding southern elephant seal population on Marion Island using the IPM-tLTRE framework, applied to count and mark-recapture data on 9500 female seals over nearly 40 years. Given the uncertainty around IPM-tLTRE estimates of immigration, we also aimed to investigate the utility of simulation and sensitivity analyses as general tools for evaluating the robustness of conclusions obtained in this framework. Using a Bayesian IPM and tLTRE analysis, we quantified the contributions of survival, immigration and population structure to population growth. We assessed the sensitivity of our estimates to choice of multivariate priors on immigration and other vital rates. To do so we make a novel application of Gaussian process priors, in comparison with commonly used shrinkage priors. Using simulation, we assessed our model's ability to estimate the demographic contribution of immigration under different levels of temporal variance in immigration. The tLTRE analysis suggested that adult survival and immigration were the most important drivers of recent population growth. While the contribution of immigration was sensitive to prior choices, the estimate was consistently large. Furthermore, our simulation study validated the importance of immigration by showing that our estimate of its demographic contribution is unlikely to result as a biased overestimate. Our results highlight the connectivity between distant populations of southern elephant seals, illustrating that female dispersal can be important in regulating the abundance of local populations even when natal site fidelity is high. More generally, we demonstrate how robust ecological conclusions may be obtained about immigration from the IPM-tLTRE framework, by combining sensitivity analysis and simulation.
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Affiliation(s)
- Murray Christian
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Hatfield, South Africa
- Centre for Statistics in Ecology, the Environment and Conservation, Department of Statistical Sciences, University of Cape Town, Cape Town, South Africa
| | - W Chris Oosthuizen
- Centre for Statistics in Ecology, the Environment and Conservation, Department of Statistical Sciences, University of Cape Town, Cape Town, South Africa
| | - Marthán N Bester
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Hatfield, South Africa
| | - P J Nico de Bruyn
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Hatfield, South Africa
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2
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Sauve D, Charmantier A, Hatch SA, Friesen VL. The magnitude of selection on growth varies among years and increases under warming conditions in a subarctic seabird. Evol Lett 2024; 8:56-63. [PMID: 38370550 PMCID: PMC10871900 DOI: 10.1093/evlett/qrad001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 12/19/2022] [Accepted: 01/24/2023] [Indexed: 02/20/2024] Open
Abstract
Because of ongoing rapid climate change, many ecosystems are becoming both warmer and more variable, and these changes are likely to alter the magnitude and variability of natural selection acting on wild populations. Critically, changes and fluctuations in selection can impact both population demography and evolutionary change. Therefore, predicting the impacts of climate change depends on understanding the magnitude and variation in selection on traits across different life stages and environments. Long-term experiments in wild settings are a great opportunity to determine the impact of environmental conditions on selection. Here we examined variability in the strength of selection on size traits of nestling black-legged kittiwakes (Rissa tridactyla) in a 25-year study including a food supplementation experiment on Middleton Island in the Gulf of Alaska. Using mixed effect models, we examined the annual variability of stage-specific and resource-specific selection gradients across 25 years. We found that (a) larger and heavier hatchlings were the most likely to survive during early ontogeny, (b) non-food supplemented younger nestlings in a brood experienced the strongest selection, and (c) warmer conditions increased the magnitude of selection on nestling mass and affected non-food supplemented and second-hatched nestlings the most. Our results suggested that variable resource dynamics likely caused some of the changes in selection from year to year and that warming conditions increased the strength of selection on subarctic seabird growth. However, our experimental manipulation revealed that local environmental heterogeneity could buffer the selection expected from broader climatic changes. Consequently, understanding the interactive effects of local conditions and general changes in climate seems likely to improve our ability to predict future selection gradients.
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Affiliation(s)
- Drew Sauve
- Department of Biology, Queen’s University, Kingston, Ontario, Canada
| | | | - Scott A Hatch
- Institute for Seabird Research and Conservation, Anchorage, AK, United States
| | - Vicki L Friesen
- Department of Biology, Queen’s University, Kingston, Ontario, Canada
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3
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Beltran RS, Hernandez KM, Condit R, Robinson PW, Crocker DE, Goetsch C, Kilpatrick AM, Costa DP. Physiological tipping points in the relationship between foraging success and lifetime fitness of a long-lived mammal. Ecol Lett 2023; 26:706-716. [PMID: 36888564 DOI: 10.1111/ele.14193] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 03/09/2023]
Abstract
Although anthropogenic change is often gradual, the impacts on animal populations may be precipitous if physiological processes create tipping points between energy gain, reproduction or survival. We use 25 years of behavioural, diet and demographic data from elephant seals to characterise their relationships with lifetime fitness. Survival and reproduction increased with mass gain during long foraging trips preceding the pupping seasons, and there was a threshold where individuals that gained an additional 4.8% of their body mass (26 kg, from 206 to 232 kg) increased lifetime reproductive success three-fold (from 1.8 to 4.9 pups). This was due to a two-fold increase in pupping probability (30% to 76%) and a 7% increase in reproductive lifespan (6.0 to 6.4 years). The sharp threshold between mass gain and reproduction may explain reproductive failure observed in many species and demonstrates how small, gradual reductions in prey from anthropogenic disturbance could have profound implications for animal populations.
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Affiliation(s)
- Roxanne S Beltran
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA
| | - Keith M Hernandez
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA.,Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, California, USA
| | - Richard Condit
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA
| | - Patrick W Robinson
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, California, USA
| | - Chandra Goetsch
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA
| | - A Marm Kilpatrick
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California, USA.,Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, California, USA
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4
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Volzke S, Cleeland JB, Hindell MA, Corney SP, Wotherspoon SJ, McMahon CR. Extreme polygyny results in intersex differences in age-dependent survival of a highly dimorphic marine mammal. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221635. [PMID: 36968236 PMCID: PMC10031410 DOI: 10.1098/rsos.221635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/02/2023] [Indexed: 06/18/2023]
Abstract
Developmental differences in vital rates are especially profound in polygamous mating systems. Southern elephant seals (Mirounga leonina) are highly dimorphic and extremely polygynous marine mammals. A demographic model, supported by long-term capture-mark-recapture records, investigated the influence of sex and age on survival in this species. The study revealed clear differences between female and male age-dependent survival rates. Overall juvenile survival estimates were stable around 80-85% for both sexes. However, male survival estimates were 5-10% lower than females in the same age classes until 8 years of age. At this point, male survival decreased rapidly to 50% ± 10% while female estimates remained constant at 80% ± 5%. Different energetic requirements could underpin intersex differences in adult survival. However, the species' strong sexual dimorphism diverges during early juvenile development when sex-specific survival rates were less distinct. Maximizing growth is especially advantageous for males, with size being a major determinant of breeding probability. Maturing males may employ a high-risk high-reward foraging strategy to compensate for extensive sexual selection pressures and sex-specific energetic needs. Our findings suggest sex-specific adult survival is a result of in situ ecological interactions and evolutionary specialization associated with being a highly polygynous marine predator.
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Affiliation(s)
- Sophia Volzke
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7005, Australia
- Australian Antarctic Division, Department of Agriculture, Water and the Environment, Kingston, TAS 7050, Australia
| | - Jaimie B. Cleeland
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7005, Australia
- Australian Antarctic Division, Department of Agriculture, Water and the Environment, Kingston, TAS 7050, Australia
| | - Mark A. Hindell
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7005, Australia
| | - Stuart P. Corney
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7005, Australia
- Centre for Marine Socioecology, University of Tasmania, Hobart, TAS 7005, Australia
- Australian Antarctic Partnership Program, University of Tasmania, Hobart, TAS 7005, Australia
| | - Simon J. Wotherspoon
- Australian Antarctic Division, Department of Agriculture, Water and the Environment, Kingston, TAS 7050, Australia
| | - Clive R. McMahon
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7005, Australia
- IMOS Animal Tagging, Sydney Institute of Marine Science, Mosman, NSW 2088, Australia
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5
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McHuron EA, Adamczak S, Arnould JPY, Ashe E, Booth C, Bowen WD, Christiansen F, Chudzinska M, Costa DP, Fahlman A, Farmer NA, Fortune SME, Gallagher CA, Keen KA, Madsen PT, McMahon CR, Nabe-Nielsen J, Noren DP, Noren SR, Pirotta E, Rosen DAS, Speakman CN, Villegas-Amtmann S, Williams R. Key questions in marine mammal bioenergetics. CONSERVATION PHYSIOLOGY 2022; 10:coac055. [PMID: 35949259 PMCID: PMC9358695 DOI: 10.1093/conphys/coac055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/28/2022] [Accepted: 07/20/2022] [Indexed: 06/15/2023]
Abstract
Bioenergetic approaches are increasingly used to understand how marine mammal populations could be affected by a changing and disturbed aquatic environment. There remain considerable gaps in our knowledge of marine mammal bioenergetics, which hinder the application of bioenergetic studies to inform policy decisions. We conducted a priority-setting exercise to identify high-priority unanswered questions in marine mammal bioenergetics, with an emphasis on questions relevant to conservation and management. Electronic communication and a virtual workshop were used to solicit and collate potential research questions from the marine mammal bioenergetic community. From a final list of 39 questions, 11 were identified as 'key' questions because they received votes from at least 50% of survey participants. Key questions included those related to energy intake (prey landscapes, exposure to human activities) and expenditure (field metabolic rate, exposure to human activities, lactation, time-activity budgets), energy allocation priorities, metrics of body condition and relationships with survival and reproductive success and extrapolation of data from one species to another. Existing tools to address key questions include labelled water, animal-borne sensors, mark-resight data from long-term research programs, environmental DNA and unmanned vehicles. Further validation of existing approaches and development of new methodologies are needed to comprehensively address some key questions, particularly for cetaceans. The identification of these key questions can provide a guiding framework to set research priorities, which ultimately may yield more accurate information to inform policies and better conserve marine mammal populations.
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Affiliation(s)
- Elizabeth A McHuron
- Corresponding author: Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington, WA, 98195, USA.
| | - Stephanie Adamczak
- Ecology and Evolutionary Biology Department, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
| | - John P Y Arnould
- School of Life and Environmental Sciences, Deakin University, Burwood, VIC 3125, Australia
| | - Erin Ashe
- Oceans Initiative, Seattle, WA, 98102, USA
| | - Cormac Booth
- SMRU Consulting, Scottish Oceans Institute, University of St. Andrews, St. Andrews KY16 8LB, UK
| | - W Don Bowen
- Biology Department, Dalhousie University, Halifax, NS B3H 4R2, Canada
- Population Ecology Division, Bedford Institute of Oceanography, Dartmouth, NS B2Y 4A2, Canada
| | - Fredrik Christiansen
- Aarhus Institute of Advanced Studies, 8000 Aarhus C, Denmark
- Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark
- Center for Sustainable Aquatic Ecosystems, Harry Butler Institute, Murdoch, Murdoch University, WA 6150, Australia
| | - Magda Chudzinska
- SMRU Consulting, Scottish Oceans Institute, University of St. Andrews, St. Andrews KY16 8LB, UK
- Sea Mammal Research Unit, Scottish Oceans Institute, University of St. Andrews, St. Andrews KY16 9XL, UK
| | - Daniel P Costa
- Ecology and Evolutionary Biology Department, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
| | - Andreas Fahlman
- Fundación Oceanogràfic de la Comunitat Valenciana, 46005 Valencia, Spain
- Kolmården Wildlife Park, 618 92 Kolmården, Sweden
| | - Nicholas A Farmer
- NOAA/National Marine Fisheries Service, Southeast Regional Office, St. Petersburg, FL, 33701, USA
| | - Sarah M E Fortune
- Department of Oceanography, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Cara A Gallagher
- Plant Ecology and Nature Conservation, University of Potsdam, 14476 Potsdam, Germany
| | - Kelly A Keen
- Ecology and Evolutionary Biology Department, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
| | - Peter T Madsen
- Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus C, Denmark
| | - Clive R McMahon
- IMOS Animal Tagging, Sydney Institute of Marine Science, Mosman, NSW 2088, Australia
| | | | - Dawn P Noren
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA, 98112, USA
| | - Shawn R Noren
- Institute of Marine Science, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Enrico Pirotta
- Centre for Research into Ecological and Environmental Modelling, University of St. Andrews, St. Andrews KY16 9LZ, UK
| | - David A S Rosen
- Institute for Oceans and Fisheries, University of British Columbia, Vancouver, BC V6T 1ZA, Canada
| | - Cassie N Speakman
- School of Life and Environmental Sciences, Deakin University, Burwood, VIC 3125, Australia
| | - Stella Villegas-Amtmann
- Ecology and Evolutionary Biology Department, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
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6
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Negrete J, Juáres M, Mennucci JA, Daneri G. Population status of southern elephant seals (Mirounga leonina) at Peninsula Potter breeding colony, Antarctica. Polar Biol 2022. [DOI: 10.1007/s00300-022-03044-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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7
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Holser RR, Crocker DE, Robinson PW, Condit R, Costa DP. Density-dependent effects on reproductive output in a capital breeding carnivore, the northern elephant seal ( Mirounga angustirostris). Proc Biol Sci 2021; 288:20211258. [PMID: 34641731 PMCID: PMC8511744 DOI: 10.1098/rspb.2021.1258] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 09/17/2021] [Indexed: 11/12/2022] Open
Abstract
All organisms face resource limitations that will ultimately restrict population growth, but the controlling mechanisms vary across ecosystems, taxa, and reproductive strategies. Using four decades of data, we examine how variation in the environment and population density affect reproductive outcomes in a capital-breeding carnivore, the northern elephant seal (Mirounga angustirostris). This species provides a unique opportunity to examine the relative importance of resource acquisition and density-dependence on breeding success. Capital breeders accrue resources over large temporal and spatial scales for use during an abbreviated reproductive period. This strategy may have evolved, in part, to confer resilience to short-term environmental variability. We observed density-dependent effects on weaning mass, and maternal age (experience) was more important than oceanographic conditions or maternal mass in determining offspring weaning mass. Together these findings show that the mechanisms controlling reproductive output are conserved across terrestrial and marine systems and vary with population dynamics, an important consideration when assessing the effect of extrinsic changes, such as climate change, on a population.
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Affiliation(s)
- Rachel R. Holser
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Daniel E. Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA 94928, USA
| | - Patrick W. Robinson
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Richard Condit
- Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, IL 60605, USA
- Morton Arboretum, 4100 Illinois Route 53, Lisle, IL 60532, USA
| | - Daniel P. Costa
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, 130 McAllister Way, Santa Cruz, CA 95060, USA
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8
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Oosthuizen WC, Péron G, Pradel R, Bester MN, de Bruyn PJN. Positive early-late life-history trait correlations in elephant seals. Ecology 2021; 102:e03288. [PMID: 33481267 DOI: 10.1002/ecy.3288] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/12/2020] [Indexed: 01/24/2023]
Abstract
Correlations between early- and late-life performance are a major prediction of life-history theory. Negative early-late correlations can emerge because biological processes are optimized for early but not late life (e.g., rapid development may accelerate the onset of senescence; "developmental theory of aging") or because allocation to early-life performance comes at a cost in terms of late-life performance (as in the disposable soma theory). But variation in genetic and environmental challenges that each individual has to cope with during early life may also lead to positive early-late life-history trait correlations (the "fixed heterogeneity" or "individual quality" hypothesis). We analyzed individual life-history trajectories of 7,420 known-age female southern elephant seals (Mirounga leonina) monitored over 36 yr to determine how actuarial senescence (a proxy for late-life performance) correlate with age at first reproduction (a proxy for early-life performance). As some breeding events may not be detected in this field study, we used a custom "multievent" hierarchical model to estimate the age at first reproduction and correlate it to other life-history traits. The probability of first reproduction was 0.34 at age 3, with most females breeding for the first time at age 4, and comparatively few at older ages. Females with an early age of first reproduction outperformed delayed breeders in all aspects we considered (survival, rate of senescence, net reproductive output) but one: early breeders appeared to have an onset of actuarial senescence 1 yr earlier compared to late breeders. Genetics and environmental conditions during early life likely explain the positive correlation between early- and late-life performance. Our results provide the first evidence of actuarial senescence in female southern elephant seals.
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Affiliation(s)
- W Chris Oosthuizen
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa.,Marine Apex Predator Research Unit, Institute for Coastal and Marine Research and Department of Zoology, Nelson Mandela University, Port Elizabeth, 6031, South Africa
| | - Guillaume Péron
- CNRS, Laboratoire de Biométrie et Biologie Évolutive, UMR5558, Université de Lyon, Université Lyon 1, Villeurbanne, France
| | - Roger Pradel
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier, France
| | - Marthán N Bester
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
| | - P J Nico de Bruyn
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, 0028, South Africa
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9
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Hindell MA, McMahon CR, Jonsen I, Harcourt R, Arce F, Guinet C. Inter- and intrasex habitat partitioning in the highly dimorphic southern elephant seal. Ecol Evol 2021; 11:1620-1633. [PMID: 33613994 PMCID: PMC7882946 DOI: 10.1002/ece3.7147] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 11/25/2020] [Accepted: 12/02/2020] [Indexed: 01/15/2023] Open
Abstract
Partitioning resources is a key mechanism for avoiding intraspecific competition and maximizing individual energy gain. However, in sexually dimorphic species it is difficult to discern if partitioning is due to competition or the different resource needs of morphologically distinct individuals. In the highly dimorphic southern elephant seal, there are intersexual differences in habitat use; at Iles Kerguelen, males predominantly use shelf waters, while females use deeper oceanic waters. There are equally marked intrasexual differences, with some males using the nearby Kerguelen Plateau, and others using the much more distant Antarctic continental shelf (~2,000 km away). We used this combination of inter and intrasexual behavior to test two hypotheses regarding habitat partitioning in highly dimorphic species. (a) that intersexual differences in habitat use will not appear until the seals diverge in body size and (b) that some habitats have higher rates of energy return than others. In particular, that the Antarctic shelf would provide higher energy returns than the Kerguelen Shelf, to offset the greater cost of travel. We quantified the habitat use of 187 southern elephant seals (102 adult females and 85 subadult males). The seals in the two groups were the same size (~2.4 m) removing the confounding effect of body size. We found that the intersexual differences in habitat use existed before the divergence in body size. Also, we found that the amount of energy gained was the same in all of the major habitats. This suggests that the use of shelf habitats by males is innate, and a trade-off between the need to access the large benthic prey available on shelf waters, against the higher risk of predation there. Intrasexual differences in habitat use are another trade-off; although there are fewer predators on the Antarctic shelf, it is subject to considerable interannual fluctuations in sea-ice extent. In contrast, the Kerguelen Plateau presents more consistent foraging opportunities, but contains higher levels of predation. Habitat partitioning in this highly dimorphic species is therefore the result of complex interplay of life history strategies, environmental conditions and predation pressure.
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Affiliation(s)
- Mark A. Hindell
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
| | - Clive R. McMahon
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
- IMOS Animal Tagging, Sydney Institute of Marine ScienceMosmanNew South WalesAustralia
- Department of Biological SciencesMacquarie UniversityNorth Ryde, SydneyNew South WalesAustralia
| | - Ian Jonsen
- Department of Biological SciencesMacquarie UniversityNorth Ryde, SydneyNew South WalesAustralia
| | - Robert Harcourt
- IMOS Animal Tagging, Sydney Institute of Marine ScienceMosmanNew South WalesAustralia
- Department of Biological SciencesMacquarie UniversityNorth Ryde, SydneyNew South WalesAustralia
| | - Fernando Arce
- Institute for Marine and Antarctic StudiesUniversity of TasmaniaHobartTasmaniaAustralia
| | - Christophe Guinet
- Centre d’Etudes Biologiques de Chizé (CEBC)UMR 7372Université de la Rochelle‐CNRSVilliers en BoisFrance
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10
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Mestre J, Authier M, Cherel Y, Harcourt R, McMahon CR, Hindell MA, Charrassin JB, Guinet C. Decadal changes in blood δ 13C values, at-sea distribution, and weaning mass of southern elephant seals from Kerguelen Islands. Proc Biol Sci 2020; 287:20201544. [PMID: 32811318 PMCID: PMC7482287 DOI: 10.1098/rspb.2020.1544] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 07/27/2020] [Indexed: 11/12/2022] Open
Abstract
Changes in the foraging environment and at-sea distribution of southern elephant seals from Kerguelen Islands were investigated over a decade (2004-2018) using tracking, weaning mass, and blood δ13C values. Females showed either a sub-Antarctic or an Antarctic foraging strategy, and no significant shift in their at-sea distribution was detected between 2004 and 2017. The proportion of females foraging in sub-Antarctic versus Antarctic habitats did not change over the 2006-2018 period. Pup weaning mass varied according to the foraging habitat of their mothers. The weaning mass of sub-Antarctic foraging mothers' pups decreased by 11.7 kg over the study period, but they were on average 5.8 kg heavier than pups from Antarctic foraging mothers. Pup blood δ13C values decreased by 1.1‰ over the study period regardless of their sex and the presumed foraging habitat of their mothers. Together, these results suggest an ecological change is occurring within the Indian sector of the Southern Ocean with possible consequences on the foraging performance of southern elephant seals. We hypothesize that this shift in δ13C is related to a change in primary production and/or in the composition of phytoplankton communities, but this requires further multidisciplinary investigations.
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Affiliation(s)
- Julie Mestre
- Centre d'Etudes Biologiques de Chizé (CEBC), UMR 7372 du CNRS-La Rochelle Université, 79360 Villiers-en-Bois, France
- Sorbonne Université, Collège Doctoral, F-75005 Paris, France
| | - Matthieu Authier
- Observatoire PELAGIS, UMS 3462 La Rochelle Université and CNRS, La Rochelle, France
- ADERA, Pessac Cedex, France
| | - Yves Cherel
- Centre d'Etudes Biologiques de Chizé (CEBC), UMR 7372 du CNRS-La Rochelle Université, 79360 Villiers-en-Bois, France
| | - Rob Harcourt
- Department of Biological Sciences, Macquarie University, North Ryde, NSW, Australia
| | - Clive R. McMahon
- Department of Biological Sciences, Macquarie University, North Ryde, NSW, Australia
- IMOS Animal Tagging, Sydney Institute of Marine Science, Sydney, NSW, Australia
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
| | - Mark A. Hindell
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
| | | | - Christophe Guinet
- Centre d'Etudes Biologiques de Chizé (CEBC), UMR 7372 du CNRS-La Rochelle Université, 79360 Villiers-en-Bois, France
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11
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Lloyd KJ, Oosthuizen WC, Fay R, Bester MN, Nico de Bruyn PJ. Selective disappearance of frail juveniles: consequences for understanding social dominance in adult male elephant seals. OIKOS 2020. [DOI: 10.1111/oik.07434] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Kyle J. Lloyd
- Mammal Research Inst., Dept of Zoology and Entomology, Univ. of Pretoria Pretoria South Africa
- Landscape Conservation Programme, BirdLife South Africa Pinegowrie South Africa
| | - W. Chris Oosthuizen
- Mammal Research Inst., Dept of Zoology and Entomology, Univ. of Pretoria Pretoria South Africa
- Marine Apex Predator Research Unit, Zoology Dept, Nelson Mandela Univ. Port Elizabeth South Africa
| | - Rémi Fay
- Swiss Ornithological Institute Seerose Sempach Switzerland
| | - Marthán N. Bester
- Mammal Research Inst., Dept of Zoology and Entomology, Univ. of Pretoria Pretoria South Africa
| | - P. J. Nico de Bruyn
- Mammal Research Inst., Dept of Zoology and Entomology, Univ. of Pretoria Pretoria South Africa
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12
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Osiecka AN, Fearey J, Elwen S, Gridley T. Prolonged nursing in Cape fur seals (Arctocephalus pusillus pusillus) at Cape Cross colony, Namibia. AFRICAN ZOOLOGY 2020. [DOI: 10.1080/15627020.2020.1768144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Anna N Osiecka
- Sea Search Research and Conservation NPC, Cape Town, South Africa
| | - Jack Fearey
- Sea Search Research and Conservation NPC, Cape Town, South Africa
- Department of Statistical Sciences, University of Cape Town, Western Cape, South Africa
| | - Simon Elwen
- Sea Search Research and Conservation NPC, Cape Town, South Africa
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa
| | - Tess Gridley
- Sea Search Research and Conservation NPC, Cape Town, South Africa
- Department of Statistical Sciences, University of Cape Town, Western Cape, South Africa
- Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa
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13
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Oosthuizen WC, Postma M, Altwegg R, Nevoux M, Pradel R, Bester MN, Bruyn PJN. Individual heterogeneity in life‐history trade‐offs with age at first reproduction in capital breeding elephant seals. POPUL ECOL 2019. [DOI: 10.1002/1438-390x.12015] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- W. Chris Oosthuizen
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Hatfield South Africa
| | - Martin Postma
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Hatfield South Africa
| | - Res Altwegg
- Centre for Statistics in Ecology Environment and Conservation, Department of Statistical Sciences University of Cape Town Rondebosch South Africa
- African Climate and Development Initiative, University of Cape Town Rondebosch South Africa
| | - Marie Nevoux
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Hatfield South Africa
- UMRESE, Ecology and Ecosystem Health, Agrocampus Ouest, INRA Rennes France
| | - Roger Pradel
- Biostatistics and Population Biology Group, CEFE, CNRS, University of Montpellier Montpellier France
| | - Marthán N. Bester
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Hatfield South Africa
| | - P. J. Nico Bruyn
- Mammal Research Institute, Department of Zoology and Entomology University of Pretoria Hatfield South Africa
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14
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Reproductive success delays moult phenology in a polar mammal. Sci Rep 2019; 9:5221. [PMID: 30914781 PMCID: PMC6435649 DOI: 10.1038/s41598-019-41635-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 03/12/2019] [Indexed: 02/02/2023] Open
Abstract
Animals can respond to dynamic environments through phenological plasticity of life history events; however, changes in one part of the annual cycle can diminish the success of subsequent life history events. Our aims were to determine the associations between reproduction and moult phenology across years and to quantify phenological plasticity across varying environmental conditions. We conducted demographic surveys of 4,252 flipper-tagged Weddell seals (Leptonychotes weddellii) in the Ross Sea, Antarctica during four austral summers. At each sighting, seals were assigned a moult code based on the visible presence of new fur and the start date of each animal’s moult was back-calculated. Reproductive success and parturition dates were obtained for the breeding season prior to and following the moult. We found that successful reproduction delayed moult by 16 days relative to non-parturient females. Phenology of the intervening moult was indicative of previous reproductive dynamics but not predictive of subsequent reproductive outcomes. Across years, moult phenology varied by about two weeks and covaried strongly with sea ice break-out timing for all reproductive categories. Our findings suggest these polar mammals have some flexibility within the annual cycle that allows adjustment of moult phenology to fluctuating environmental conditions without compromising future reproductive success.
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15
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Salogni E, Galimberti F, Sanvito S, Miller E. Male and female pups of the highly sexually dimorphic northern elephant seal (Mirounga angustirostris) differ slightly in body size. CAN J ZOOL 2019. [DOI: 10.1139/cjz-2018-0220] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In mammals, males generally are larger than females, though such sexual-size differences have been documented primarily in adults and are relatively poorly known in early life. We studied sexual-size differences in pups of the northern elephant seal (Mirounga angustirostris (Gill, 1866)), which in adulthood is one of the most sexually dimorphic mammals. We studied body size at birth and weaning, at Islas San Benito, Mexico, at the southernmost limit of the species’ breeding range. Males were 10% heavier and 2% longer than females at birth. Sexes did not differ significantly in either measure of body size at weaning, although males were slightly heavier (4%) and longer (1%) than females. Neither growth rate nor suckling duration differed between the sexes. In previous studies in California, USA, pups at weaning were heavier than in our study, and males were heavier than females. These differences may reflect ecological, temporal, or life-history differences across populations. The modest difference in sexual-size dimorphism early in life in this species compared with the great difference in adulthood likely reflects multiple selective forces, including constraints on neonatal size set by body size of females, and the weakness of sexual selection at that stage of life.
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Affiliation(s)
- E. Salogni
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL A1B 3X9, Canada
- Elephant Seal Research Group, Sea Lion Island, Falkland Islands, FIQQ 1ZZ
| | - F. Galimberti
- Elephant Seal Research Group, Sea Lion Island, Falkland Islands, FIQQ 1ZZ
| | - S. Sanvito
- Elephant Seal Research Group, Sea Lion Island, Falkland Islands, FIQQ 1ZZ
| | - E.H. Miller
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL A1B 3X9, Canada
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16
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Oosthuizen WC, Pradel R, Bester MN, de Bruyn PJN. Making use of multiple surveys: Estimating breeding probability using a multievent-robust design capture-recapture model. Ecol Evol 2019; 9:836-848. [PMID: 30766673 PMCID: PMC6362610 DOI: 10.1002/ece3.4828] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 07/24/2018] [Accepted: 09/05/2018] [Indexed: 11/12/2022] Open
Abstract
Increased environmental stochasticity due to climate change will intensify temporal variance in the life-history traits, and especially breeding probabilities, of long-lived iteroparous species. These changes may decrease individual fitness and population viability and is therefore important to monitor. In wild animal populations with imperfect individual detection, breeding probabilities are best estimated using capture-recapture methods. However, in many vertebrate species (e.g., amphibians, turtles, seabirds), nonbreeders are unobservable because they are not tied to a territory or breeding location. Although unobservable states can be used to model temporary emigration of nonbreeders, there are disadvantages to having unobservable states in capture-recapture models. The best solution to deal with unobservable life-history states is therefore to eliminate them altogether. Here, we achieve this objective by fitting novel multievent-robust design models which utilize information obtained from multiple surveys conducted throughout the year. We use this approach to estimate annual breeding probabilities of capital breeding female elephant seals (Mirounga leonina). Conceptually, our approach parallels a multistate version of the Barker/robust design in that it combines robust design capture data collected during discrete breeding seasons with observations made at other times of the year. A substantial advantage of our approach is that the nonbreeder state became "observable" when multiple data sources were analyzed together. This allowed us to test for the existence of state-dependent survival (with some support found for lower survival in breeders compared to nonbreeders), and to estimate annual breeding transitions to and from the nonbreeder state with greater precision (where current breeders tended to have higher future breeding probabilities than nonbreeders). We used program E-SURGE (2.1.2) to fit the multievent-robust design models, with uncertainty in breeding state assignment (breeder, nonbreeder) being incorporated via a hidden Markov process. This flexible modeling approach can easily be adapted to suit sampling designs from numerous species which may be encountered during and outside of discrete breeding seasons.
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Affiliation(s)
- W. Chris Oosthuizen
- Department of Zoology and EntomologyMammal Research InstituteUniversity of PretoriaHatfieldSouth Africa
| | - Roger Pradel
- Biostatistics and Population Biology GroupCEFE, CNRS, Univ Montpellier, Univ Paul Valéry Montpellier 3, EPHE, IRDMontpellierFrance
| | - Marthán N. Bester
- Department of Zoology and EntomologyMammal Research InstituteUniversity of PretoriaHatfieldSouth Africa
| | - P. J. Nico de Bruyn
- Department of Zoology and EntomologyMammal Research InstituteUniversity of PretoriaHatfieldSouth Africa
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17
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Griffen BD. Reproductive skipping as an optimal life history strategy in the southern elephant seal, Mirounga leonina. Ecol Evol 2018; 8:9158-9170. [PMID: 30377491 PMCID: PMC6194220 DOI: 10.1002/ece3.4408] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 07/03/2018] [Accepted: 07/04/2018] [Indexed: 11/19/2022] Open
Abstract
Intermittent breeding by which organisms skip some current reproductive opportunities in order to enhance future reproductive success is a common life history trade-off among long-lived, iteroparous species. The southern elephant seal Mirounga leonina engages in intermediate breeding when body condition is low. While it is anticipated that this strategy may increase the lifetime reproductive output of this species, the conditions under which reproductive skipping are predicted to occur are not clear. Here I develop a dynamic state variable model based on published data that examines when southern elephant seals are predicted to optimally skip reproduction in order to maximize lifetime reproductive output as a function of current body mass, maternal age, and survivorship. I demonstrate that the optimal reproductive strategy for this species can include reproductive skipping, and that the conditions where this is optimal depend on patterns of mass-dependent adult female survival. I further show that intermittent breeding can increase lifetime reproductive output, and that the magnitude of this benefit increases with the ability of individual animals to replenish depleted body mass through foraging. Finally, I show that when the environment is variable and foraging is reduced in bad years, the benefit of adopting an optimal strategy that includes reproductive skipping increases asymptotically with the frequency of bad years. These results highlight the importance of characterizing the pattern of adult survival in this species, as well as the need to identify other factors that may influence the prevalence and benefits of reproductive skipping.
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