Journal Article

Interacting effects of unobserved heterogeneity and individual stochasticity in the life history of the southern fulmar

Woods Hole Oceanographic Institution (WHOI), Aubry, Lise, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC) ; Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Jenouvrier, Stéphanie, Institute for Biodiversity and Ecosystem Dynamics ; Universiteit van Amsterdam = University of Amsterdam (UvA), Colorado State University [Fort Collins] (CSU), Barbraud, Christophe, Weimerskirch, Henri, Caswell, Hal

2018

Overview

1. Individuals are heterogeneous in many ways. Some of these differences are incorporatedas individual states (e.g. age, size, breeding status) in population models.However, substantial amounts of heterogeneity may remain unaccounted for, dueto unmeasurable genetic, maternal or environmental factors.2. Such unobserved heterogeneity (UH) affects the behaviour of heterogeneous cohortsvia intra-cohort selection and contributes to inter-individual variance in demographicoutcomes such as longevity and lifetime reproduction. Variance is alsoproduced by individual stochasticity, due to random events in the life cycle of wildorganisms, yet no study thus far has attempted to decompose the variance in demographicoutcomes into contributions from UH and individual stochasticity for ananimal population in the wild.3. We developed a stage-classified matrix population model for the southern fulmarbreeding on Ile des Pétrels, Antarctica. We applied multievent, multistate mark–recapturemethods to estimate a finite mixture model accounting for UH in all vitalrates and Markov chain methods to calculate demographic outcomes. Finally, wepartitioned the variance in demographic outcomes into contributions from UH andindividual stochasticity.4. We identify three UH groups, differing substantially in longevity, lifetime reproductiveoutput, age at first reproduction and in the proportion of the life spent in eachreproductive state.– 14% of individuals at fledging have a delayed but high probability of recruitmentand extended reproductive life span.– 67% of individuals are less likely to reach adulthood, recruit late and skip breedingoften but have the highest adult survival rate.– 19% of individuals recruit early and attempt to breed often. They are likely to raisetheir offspring successfully, but experience a relatively short life span.Unobserved heterogeneity only explains a small fraction of the variances in longevity(5.9%), age at first reproduction (3.7%) and lifetime reproduction (22%).5. UH can affect the entire life cycle, including survival, development and reproductiverates, with consequences over the lifetime of individuals and impacts on cohort dynamics. The respective role of UH vs. individual stochasticity varies greatly amongdemographic outcomes. We discuss the implication of our finding for the gradient oflife-history strategies observed among species and argue that individual differencesshould be accounted for in demographic studies of wild populations.

• Publisher: Wiley,CCSD,John Wiley & Sons Ltd,Blackwell Publishing Ltd,John Wiley and Sons Inc
• Subject: adulthood / adults / Age / Age Factors / Animal populations / Animals / Antarctic Regions / Antarctica / Birds - physiology / breeding / Breeding status / Demographics / Environmental factors / Environmental Sciences / fledglings / frailty / Heterogeneity / individual quality / latent / Life cycles / life expectancy / Life Histories / Life history / Life History Traits / Life span / lifetime reproductive success / Longevity / mark-recapture studies / Markov chain / Markov chains / Models, Biological / Offspring / Population studies / Probabilistic models / progeny / Recruitment / Reproduction / reproductive performance / Stochastic Processes / Stochasticity / Survival / survival rate / Variance