Publication Date:
2022-05-26
Description:
Author Posting. © Ecological Society of America, 2019. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Monographs 89(4), (2019): e01388, doi:10.1002/ecm.1388.
Description:
Ecologists widely acknowledge that a complex interplay of endogenous (density‐dependent) and exogenous (density‐independent) factors impact demographic processes. Individuals respond differently to those forces, ultimately shaping the dynamics of wild populations. Most comprehensive studies disentangling simultaneously the effects of density dependence, climate, and prey abundance while taking into account age structure were conducted in terrestrial ecosystems. However, studies on marine populations are lacking. Here we provide insight into the mechanisms affecting four vital rates of an apex Antarctic marine predator population, the South Polar Skua Catharacta maccormicki, by combining a nearly half‐century longitudinal time series of individual life histories and abundance data, with climatic and prey abundance covariates. Using multistate capture–mark–recapture models, we estimated age classes effects on survival, breeding, successful breeding with one or two chicks and successful breeding with two chicks probabilities, and assessed the different effects of population size, climate, and prey abundance on each age‐specific demographic parameter. We found evidence for strong age effects in the four vital rates studied. Vital rates at younger ages were lower than those of older age classes for all parameters. Results clearly evidenced direct and indirect influences of local climate (summer sea ice concentration), of available prey resources (penguins), and of intrinsic factors (size of the breeding population). More covariate effects were found on reproductive rates than on survival, and younger age classes were more sensitive than the older ones. Results from a deterministic age‐structured density‐dependent matrix population model indicated greater effects of prey abundance and sea ice concentration on the total population size than on the breeding population size. Both total population size and the number of breeders were strongly affected by low values of sea ice concentration. Overall, our results highlight the greater sensitivity of reproductive traits and of younger age classes to prey abundance, climate variability, and density dependence in a marine apex predator, with important consequences on the total population size but with limited effects on the breeding population size. We discuss the mechanisms by which climate variability, prey abundance, and population size may affect differentially age‐specific vital rates, and the potential population consequences of future environmental changes.
Description:
We are particularly grateful to all the field workers involved in the monitoring programs on South Polar Skuas and penguins at Pointe Géologie since 1963. These long‐term demographic studies and the present work were supported financially and logistically by the French Polar Institute IPEV (program 109, resp. H. Weimerskirch), Terres Australes et Antarctiques Françaises, Zone Atelier Antarctique et Subantarctique (CNRS‐INEE), Université de La Rochelle (PhD grant N. Pacoureau), Agence Nationale de la Recherche (ANR‐16‐CE02‐0007 Democom, resp. O. Gimenez). S. Jenouvrier acknowledges support from WHOI unrestricted funds. This study is a contribution to program SENSEI (SENtinels of the Sea Ice, resp. C. Barbraud and Y. Ropert‐Coudert) funded by the BNP Paribas Foundation. Handling and manipulation of all animals were approved by the IPEV ethics committee. All animals in this study were cared for in accordance with its guidelines. We thank D. Besson for help in the data management, D. T. Iles and M. G. Neubert for constructive comments, and two anonymous reviewers for their help in improving the manuscript. C. Barbraud and N. Pacoureau designed and coordinated the research. Data management and quality check were performed by K. Delord and N. Pacoureau. Analyses were performed by N. Pacoureau with the support of C. Barbraud and S. Jenouvrier. N. Pacoureau, K. Delord, S. Jenouvrier, and C. Barbraud wrote the manuscript.
Keywords:
Adélie Penguin Pygoscelis adeliae
;
age structure
;
Antarctica
;
capture–mark–recapture
;
Catharacta maccormicki
;
density dependence
;
deterministic density‐dependent matrix population model
;
Emperor Penguin Aptenodytes forsteri
;
food availability
;
multistate model
;
sea ice concentration
Repository Name:
Woods Hole Open Access Server
Type:
Article
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