Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects
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 elepha...
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Online Access: | http://hdl.handle.net/2263/50538 https://doi.org/10.1890/ES14-00508.1 |
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ftunivpretoria:oai:repository.up.ac.za:2263/50538 2023-05-15T16:05:24+02:00 Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects Oosthuizen, Wessel Christiaan Bester, Marthan Nieuwoudt Altwegg, Res McIntyre, Trevor De Bruyn, P.J. Nico 2015-08 http://hdl.handle.net/2263/50538 https://doi.org/10.1890/ES14-00508.1 en eng Ecological Society of America http://hdl.handle.net/2263/50538 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. 2150-8925 doi:10.1890/ES14-00508.1 © 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/. CC-BY Body mass Environmental variability Food availability Marion Island Maternal effects Mirounga leonina Population Prey abundance Process variance Southern Ocean Temporal variation Top predator Article 2015 ftunivpretoria https://doi.org/10.1890/ES14-00508.1 2022-05-31T13:21:00Z 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 ... Article in Journal/Newspaper Elephant Seal Elephant Seals Marion Island Mirounga leonina Southern Elephant Seal Southern Elephant Seals Southern Ocean University of Pretoria: UPSpace Southern Ocean Ecosphere 6 8 art139 |
institution |
Open Polar |
collection |
University of Pretoria: UPSpace |
op_collection_id |
ftunivpretoria |
language |
English |
topic |
Body mass Environmental variability Food availability Marion Island Maternal effects Mirounga leonina Population Prey abundance Process variance Southern Ocean Temporal variation Top predator |
spellingShingle |
Body mass Environmental variability Food availability Marion Island Maternal effects Mirounga leonina Population Prey abundance Process variance Southern Ocean Temporal variation Top predator Oosthuizen, Wessel Christiaan Bester, Marthan Nieuwoudt Altwegg, Res McIntyre, Trevor De Bruyn, P.J. Nico Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
topic_facet |
Body mass Environmental variability Food availability Marion Island Maternal effects Mirounga leonina Population Prey abundance Process variance Southern Ocean Temporal variation Top predator |
description |
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 ... |
format |
Article in Journal/Newspaper |
author |
Oosthuizen, Wessel Christiaan Bester, Marthan Nieuwoudt Altwegg, Res McIntyre, Trevor De Bruyn, P.J. Nico |
author_facet |
Oosthuizen, Wessel Christiaan Bester, Marthan Nieuwoudt Altwegg, Res McIntyre, Trevor De Bruyn, P.J. Nico |
author_sort |
Oosthuizen, Wessel Christiaan |
title |
Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
title_short |
Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
title_full |
Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
title_fullStr |
Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
title_full_unstemmed |
Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
title_sort |
decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
publisher |
Ecological Society of America |
publishDate |
2015 |
url |
http://hdl.handle.net/2263/50538 https://doi.org/10.1890/ES14-00508.1 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Elephant Seal Elephant Seals Marion Island Mirounga leonina Southern Elephant Seal Southern Elephant Seals Southern Ocean |
genre_facet |
Elephant Seal Elephant Seals Marion Island Mirounga leonina Southern Elephant Seal Southern Elephant Seals Southern Ocean |
op_relation |
http://hdl.handle.net/2263/50538 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. 2150-8925 doi:10.1890/ES14-00508.1 |
op_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/. |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1890/ES14-00508.1 |
container_title |
Ecosphere |
container_volume |
6 |
container_issue |
8 |
container_start_page |
art139 |
_version_ |
1766401299654377472 |