DOI: 10.5061/dryad.573n5tbd7
title: Reproductive phenology is a repeatable, heritable trait linked to the timing of other life history events in a migratory marine predator

description: Population-level shifts in reproductive phenology in response to
 environmental change are common, but whether individual-level responses
 are modified by demographic and genetic factors remains less well
 understood. We used mixed models to quantify how reproductive timing
 varied across 1,755 female southern elephant seals (Mirounga leonina)
 breeding at Marion Island in the Southern Ocean (1989–2019) and to
 identify the factors that correlate with phenological shifts within- and
 between individuals. We found strong support for covariation in the timing
 of breeding arrival dates and the timing of the preceding moult. Breeding
 arrival dates were more repeatable at the individual-level, as compared to
 the population-level, even after accounting for individual traits (wean
 date as a pup, age and breeding experience) associated with phenological
 variability. Mother-daughter similarities in breeding phenology were also
 evident, indicating that additive genetic effects may contribute to
 between-individual variation in breeding phenology. Over 30 years,
 elephant seal phenology did not change towards earlier or later dates, and
 we found no correlation between annual fluctuations in phenology and
 indices of environmental variation. Our results show how maternal genetic
 (or non-genetic) effects, individual traits and linkages between cyclical
 life-history events can drive within- and between-individual variation in
 reproductive phenology.
description: From 1983 to 2019, nearly all
 elephant seal pups born at Marion Island were uniquely marked with two
 hind-flipper tags (n = 8,985 female pups) (Bester et al. 2011, Pistorius
 et al. 2011). The pups were marked at the first encounter after weaning,
 after their mothers had abandoned them. However, since 2006, we also
 marked some pre-weaned pups with ancillary tags (de Bruyn et al. 2008),
 thereby collecting pedigree information on 2,115 mother-daughter pairs.
 Data were processed in R 4.1.3 and later versions (R Core Team 2022) (see
 R script). Bester MN, de Bruyn PJN, Oosthuizen WC,
 Tosh CA, McIntyre T, Reisinger, RR et al. 2011 The Marine Mammal Programme
 at the Prince Edward Islands: 38 years of research. Afr. J. Mar. Sci. 33,
 511-521. De Bruyn PJN,
 Tosh CA, Oosthuizen WC, Phalanndwa MV, Bester MN. 2008 Temporary marking
 of unweaned southern elephant seal (<em>Mirounga</em>
 <em>leonina</em> L.) pups. S. Afr. J. Wildl. Res. 38,
 133-137. Pistorius PA, de
 Bruyn PJN, Bester MN. 2011 Population dynamics of southern elephant seals:
 a synthesis of three decades of demographic research at Marion Island.
 Afr. J. Mar. Sci. 33, 523-534. R Core Team. 2022 R: A language and
 environment for statistical computing. R Foundation for Statistical
 Computing, Vienna, Austria. URL https://www.R-project.org/.
description: Data were processed in R 4.1.3 and later versions (R Core Team
 2022). Anyone interested in using this long-term data is encouraged to
 collaborate with the authors, as their understanding of the data
 collection methods and availability of other meta-data is likely to
 enhance future analysis and interpretation.