Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density

Abstract Marine predator populations are sensitive to temporal variation in prey availability, but prey dynamics are often difficult to quantify. Long-term measures of offspring growth is a useful performance attribute to gauge the potential demographic direction for such predator populations, espec...

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Published in:Journal of Mammalogy
Main Authors: Oosthuizen, W. Chris, de Bruyn, P. J. Nico, Wege, Mia, Bester, Marthán N.
Format: Article in Journal/Newspaper
Language:English
Published: Oxford University Press (OUP) 2015
Subjects:
Online Access:http://dx.doi.org/10.1093/jmammal/gyv181
http://academic.oup.com/jmammal/article-pdf/97/2/347/38268357/jmammal_97_2_347.pdf
id croxfordunivpr:10.1093/jmammal/gyv181
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spelling croxfordunivpr:10.1093/jmammal/gyv181 2024-02-11T09:55:14+01:00 Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density Oosthuizen, W. Chris de Bruyn, P. J. Nico Wege, Mia Bester, Marthán N. 2015 http://dx.doi.org/10.1093/jmammal/gyv181 http://academic.oup.com/jmammal/article-pdf/97/2/347/38268357/jmammal_97_2_347.pdf en eng Oxford University Press (OUP) Journal of Mammalogy volume 97, issue 2, page 347-360 ISSN 1545-1542 0022-2372 Nature and Landscape Conservation Genetics Animal Science and Zoology Ecology Ecology, Evolution, Behavior and Systematics journal-article 2015 croxfordunivpr https://doi.org/10.1093/jmammal/gyv181 2024-01-12T10:11:14Z Abstract Marine predator populations are sensitive to temporal variation in prey availability, but prey dynamics are often difficult to quantify. Long-term measures of offspring growth is a useful performance attribute to gauge the potential demographic direction for such predator populations, especially where other metrics (e.g., population size estimates) are lacking. Subantarctic fur seal ( Arctocephalus tropicalis ) females are central place foragers during a protracted lactation period, and their foraging success determines the growth and vitality of their offspring. Using data spanning over 2 decades, we assessed geographic and temporal variation in growth rates and weaning mass of subantarctic fur seal pups at 2 of the species’ principal populations (Gough and Marion islands) and identified environmental conditions that may, through assumed bottom-up mechanisms, affect body mass at weaning. While Marion Island pups grew at an average rate of between 0.040 and 0.067kg/day early in lactation (comparable to conspecific growth at Amsterdam Island), the mean growth rate at Gough Island (approximately 0.030kg/day) was lower than the growth rate represented by the bottom 5% of the body mass distribution at Marion Island. Notwithstanding substantial interannual variability, we found support for a negative trend in weaning mass at both populations, suggesting a rise in limiting factors that is hypothesized to relate to concurrent local population size increases. Weaning mass tended to be higher when sea surface temperatures were warmer (with a stronger positive effect at Gough Island) and during positive phases of the Southern Oscillation Index (La Niña events), with a stronger positive effect in males. Given the low weaning mass of Gough Island fur seal pups, continued population growth here seems unlikely. While density-dependent regulation appears to have increased in strength at Marion Island, terminating rapid population growth, current weaning weights remain above the physiological limits of growth in ... Article in Journal/Newspaper Amsterdam Island Marion Island Oxford University Press Gough ENVELOPE(159.367,159.367,-81.633,-81.633) Journal of Mammalogy 97 2 347 360
institution Open Polar
collection Oxford University Press
op_collection_id croxfordunivpr
language English
topic Nature and Landscape Conservation
Genetics
Animal Science and Zoology
Ecology
Ecology, Evolution, Behavior and Systematics
spellingShingle Nature and Landscape Conservation
Genetics
Animal Science and Zoology
Ecology
Ecology, Evolution, Behavior and Systematics
Oosthuizen, W. Chris
de Bruyn, P. J. Nico
Wege, Mia
Bester, Marthán N.
Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density
topic_facet Nature and Landscape Conservation
Genetics
Animal Science and Zoology
Ecology
Ecology, Evolution, Behavior and Systematics
description Abstract Marine predator populations are sensitive to temporal variation in prey availability, but prey dynamics are often difficult to quantify. Long-term measures of offspring growth is a useful performance attribute to gauge the potential demographic direction for such predator populations, especially where other metrics (e.g., population size estimates) are lacking. Subantarctic fur seal ( Arctocephalus tropicalis ) females are central place foragers during a protracted lactation period, and their foraging success determines the growth and vitality of their offspring. Using data spanning over 2 decades, we assessed geographic and temporal variation in growth rates and weaning mass of subantarctic fur seal pups at 2 of the species’ principal populations (Gough and Marion islands) and identified environmental conditions that may, through assumed bottom-up mechanisms, affect body mass at weaning. While Marion Island pups grew at an average rate of between 0.040 and 0.067kg/day early in lactation (comparable to conspecific growth at Amsterdam Island), the mean growth rate at Gough Island (approximately 0.030kg/day) was lower than the growth rate represented by the bottom 5% of the body mass distribution at Marion Island. Notwithstanding substantial interannual variability, we found support for a negative trend in weaning mass at both populations, suggesting a rise in limiting factors that is hypothesized to relate to concurrent local population size increases. Weaning mass tended to be higher when sea surface temperatures were warmer (with a stronger positive effect at Gough Island) and during positive phases of the Southern Oscillation Index (La Niña events), with a stronger positive effect in males. Given the low weaning mass of Gough Island fur seal pups, continued population growth here seems unlikely. While density-dependent regulation appears to have increased in strength at Marion Island, terminating rapid population growth, current weaning weights remain above the physiological limits of growth in ...
format Article in Journal/Newspaper
author Oosthuizen, W. Chris
de Bruyn, P. J. Nico
Wege, Mia
Bester, Marthán N.
author_facet Oosthuizen, W. Chris
de Bruyn, P. J. Nico
Wege, Mia
Bester, Marthán N.
author_sort Oosthuizen, W. Chris
title Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density
title_short Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density
title_full Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density
title_fullStr Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density
title_full_unstemmed Geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density
title_sort geographic variation in subantarctic fur seal pup growth: linkages with environmental variability and population density
publisher Oxford University Press (OUP)
publishDate 2015
url http://dx.doi.org/10.1093/jmammal/gyv181
http://academic.oup.com/jmammal/article-pdf/97/2/347/38268357/jmammal_97_2_347.pdf
long_lat ENVELOPE(159.367,159.367,-81.633,-81.633)
geographic Gough
geographic_facet Gough
genre Amsterdam Island
Marion Island
genre_facet Amsterdam Island
Marion Island
op_source Journal of Mammalogy
volume 97, issue 2, page 347-360
ISSN 1545-1542 0022-2372
op_doi https://doi.org/10.1093/jmammal/gyv181
container_title Journal of Mammalogy
container_volume 97
container_issue 2
container_start_page 347
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