dc.contributor.author |
Oosthuizen, Wessel Christiaan
|
|
dc.contributor.author |
Bester, Marthan Nieuwoudt
|
|
dc.contributor.author |
Altwegg, Res
|
|
dc.contributor.author |
McIntyre, Trevor
|
|
dc.contributor.author |
De Bruyn, P.J. Nico
|
|
dc.date.accessioned |
2015-11-20T07:32:34Z |
|
dc.date.available |
2015-11-20T07:32:34Z |
|
dc.date.issued |
2015-08 |
|
dc.description.abstract |
Predator populations are likely to respond to bottom-up processes, but there remains limited
understanding of how wide-ranging marine predators respond to environmentally driven temporal
variation in food availability.Widespread declines of several Southern Ocean predators, including southern
elephant seals Mirounga leonina, have been attributed to decreases in food availability following
environmental changes. We used linear mixed models to examine temporal process variance in weaning
mass (a key fitness component) of southern elephant seals at Marion Island over a 27-year period (1986–
2013). We quantified the contribution of within- and between-year covariates to the total phenotypic
variance in weaning mass and determined whether the observed reversal of population decline was
associated with a continued increase in weaning mass, suggesting improvement in per capita food
availability to adult females. Weaning mass initially increased rapidly with maternal age, but reached an
asymptote when females were nine years old. Longitudinal data examining between-individual maternal
differences suggested latent, age-independent maternal influences on weaning mass. Between-year
differences accounted for only 6% of the total phenotypic variance in weaning mass.We found no evidence
for a systematic trend in weaning mass, but model predicted weaning mass was 8.70 kg (95% CI ¼ 2.14–
14.73) lower during the 1980s, suggesting that food limitation may have been most severe during these
years when the population was declining. Model support for a population size effect was entirely driven by
the low weaning mass and comparatively high (but declining) population size from 1986 to 1988;
subsequent variation in population size had no detectable influence on weaning mass. Remotely sensed
chlorophyll-a concentration within the seals’ foraging distribution explained 45% of the between-year
variation (1998–2013, n¼9) in weaning mass, with higher weaning mass in years of positive chlorophyll-a
anomalies. Environmental variation associated with variability in the Southern Annular Mode poorly
predicted temporal variation in weaning mass. Our long-term data on elephant seal weaning mass
provides a perspective on variation in food availability in a pelagic environment which is poorly known.
Examining the long-term regionally specific effects of environmental variability aids our understanding of
how these predators interact with their environment. |
en_ZA |
dc.description.librarian |
am2015 |
en_ZA |
dc.description.sponsorship |
The South African Department of Science
and Technology through the National
Research Foundation. |
en_ZA |
dc.description.uri |
http://www.esajournals.org |
en_ZA |
dc.identifier.citation |
Oosthuizen, W. C., M. N. Bester, R. Altwegg, T. McIntyre, and P. J. N. de Bruyn. 2015. Decomposing the variance in southern elephant seal weaning mass: partitioning environmental signals and maternal effects. Ecosphere 6(8):139. http://dx.DOI.org/ 10.1890/ES14-00508.1. |
en_ZA |
dc.identifier.issn |
2150-8925 |
|
dc.identifier.other |
10.1890/ES14-00508.1 |
|
dc.identifier.uri |
http://hdl.handle.net/2263/50538 |
|
dc.language.iso |
en |
en_ZA |
dc.publisher |
Ecological Society of America |
en_ZA |
dc.rights |
© 2015 Oosthuizen et al. This is an open-access article distributed under the terms of the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. http://creativecommons.org/licenses/by/3.0/. |
en_ZA |
dc.subject |
Body mass |
en_ZA |
dc.subject |
Environmental variability |
en_ZA |
dc.subject |
Food availability |
en_ZA |
dc.subject |
Marion Island |
en_ZA |
dc.subject |
Maternal effects |
en_ZA |
dc.subject |
Mirounga leonina |
en_ZA |
dc.subject |
Population |
en_ZA |
dc.subject |
Prey abundance |
en_ZA |
dc.subject |
Process variance |
en_ZA |
dc.subject |
Southern Ocean |
en_ZA |
dc.subject |
Temporal variation |
en_ZA |
dc.subject |
Top predator |
en_ZA |
dc.title |
Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
en_ZA |
dc.type |
Article |
en_ZA |