Demographic and population responses of an apex predator to climate and its prey: a long‐term study of south polar skuas

• Published in: Ecological Monographs
• Main Authors: Pacoureau, Nathan, Delord, Karine, Jenouvrier, Stéphanie, Barbraud, Christophe
• Other Authors: Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: multistate model; sea ice concentration; Adelie 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; [SDE]Environmental Sciences; Antarctic; Adelie penguin; Antarc*; Aptenodytes forsteri; Pygoscelis adeliae; Sea ice; South Polar Skuas
• Online Access: https://hal.archives-ouvertes.fr/hal-02195548; https://doi.org/10.1002/ecm.1388

International audience 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. ...