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 eleph...
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ftunivcapetownir:oai:localhost:11427/28960 2023-05-15T16:05:23+02:00 Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects Oosthuizen, W C Bester, M N Altwegg, R McIntyre, T de Bruyn, P J N 2015 application/pdf http://hdl.handle.net/11427/28960 https://open.uct.ac.za/bitstream/11427/28960/1/Oosthuizen_etal2015.pdf eng eng University of Cape Town Faculty of Science Department of Statistical Sciences http://hdl.handle.net/11427/28960 https://open.uct.ac.za/bitstream/11427/28960/1/Oosthuizen_etal2015.pdf 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 Other 2015 ftunivcapetownir 2022-09-13T05:47:03Z 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, n ¼ 9) in weaning mass, with higher weaning mass in years of positive chlorophyll-a anomalies. Environmental variation ... Other/Unknown Material Elephant Seal Elephant Seals Marion Island Mirounga leonina Southern Elephant Seal Southern Elephant Seals Southern Ocean University of Cape Town: OpenUCT Southern Ocean |
institution |
Open Polar |
collection |
University of Cape Town: OpenUCT |
op_collection_id |
ftunivcapetownir |
language |
English |
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, n ¼ 9) in weaning mass, with higher weaning mass in years of positive chlorophyll-a anomalies. Environmental variation ... |
format |
Other/Unknown Material |
author |
Oosthuizen, W C Bester, M N Altwegg, R McIntyre, T de Bruyn, P J N |
spellingShingle |
Oosthuizen, W C Bester, M N Altwegg, R McIntyre, T de Bruyn, P J N Decomposing the variance in southern elephant seal weaning mass : partitioning environmental signals and maternal effects |
author_facet |
Oosthuizen, W C Bester, M N Altwegg, R McIntyre, T de Bruyn, P J N |
author_sort |
Oosthuizen, W C |
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 |
University of Cape Town |
publishDate |
2015 |
url |
http://hdl.handle.net/11427/28960 https://open.uct.ac.za/bitstream/11427/28960/1/Oosthuizen_etal2015.pdf |
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/11427/28960 https://open.uct.ac.za/bitstream/11427/28960/1/Oosthuizen_etal2015.pdf |
op_rights |
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 |
_version_ |
1766401286974996480 |