Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island
The response of altered sex ratio in southern elephant seals due to environmental stress was analysed. Data were collected at King George Island from 1980 to 1994. Significant retreats in the ice cover during El Niño events strongly suggest environmental stress during this period along the Bellingsh...
Published in: | Marine Ecology Progress Series |
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Language: | English |
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Inter-Research
2004
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Online Access: | https://oceanrep.geomar.de/id/eprint/53772/ https://oceanrep.geomar.de/id/eprint/53772/1/4443.pdf https://doi.org/10.3354/meps268293 |
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ftoceanrep:oai:oceanrep.geomar.de:53772 2023-05-15T15:41:24+02:00 Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island Vergani, Daniel F. Stanganelli, Zulma B. Bilenca, David 2004 text https://oceanrep.geomar.de/id/eprint/53772/ https://oceanrep.geomar.de/id/eprint/53772/1/4443.pdf https://doi.org/10.3354/meps268293 en eng Inter-Research https://oceanrep.geomar.de/id/eprint/53772/1/4443.pdf Vergani, D. F., Stanganelli, Z. B. and Bilenca, D. (2004) Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island. Open Access Marine Ecology Progress Series, 268 . pp. 293-300. DOI 10.3354/meps268293 <https://doi.org/10.3354/meps268293>. doi:10.3354/meps268293 info:eu-repo/semantics/openAccess Article PeerReviewed 2004 ftoceanrep https://doi.org/10.3354/meps268293 2023-04-07T15:58:27Z The response of altered sex ratio in southern elephant seals due to environmental stress was analysed. Data were collected at King George Island from 1980 to 1994. Significant retreats in the ice cover during El Niño events strongly suggest environmental stress during this period along the Bellingshausen Sea, a zone where female elephant seals from King George Island feed during their pregnancy. Randomly chosen weaning elephant seal pups (n = 1178) were sexed at Stranger Point (King George Island, 62°14¹S, 58°30¹W) over 5 km of beach from 1985 to 1994. Adult sex ratio was also determined annually from 1980 to 1994 as the ratio between maximum number of bulls and females on land. The theoretical pup sex ratio was assumed as 1:1 according to background information. Adult sex ratio was calculated as 1:6. To define the occurrence of El Niño Southern Oscillation (ENSO) during the study period, a sea surface temperature (SST) index called ŒNiño 3.4¹ for the region 5°N to 5°S, 120°E to 170°W was considered. Monthly SST anomalies were obtained from the Climate Prediction Center (CPC, NOAA). To provide an annual index of anomaly strength (IAS), the monthly adjusted oscillation index climatology (AOIC) was averaged. Accumulated values during the whole study period showed that during El Niño years (1987, 1991, 1992) the proportion of pups was significantly biased in favour of females (p < 0.01). During normal years (1986, 1990, 1993, 1994) and La Niña years (1985, 1988, 1989), accumulative values showed a greater proportion of male pups to females (p < 0.05). Using the 1:1 hypothesis, we found during El Niño years a 9% reduction in the male segment, whereas in non-El Niño years a recovery of 7% was observed (3% during normal years and 4% during La Niña years. To see the influence of accumulative values of pup sex ratio in adult sex ratio, a theoretical adult proportion was calculated as 1:6. To test this hypothesis, information on adult sex ratio taken from King George Island between 1980 and 1994 (n = 14 yr) was ... Article in Journal/Newspaper Bellingshausen Sea Elephant Seal Elephant Seals King George Island Southern Elephant Seals OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Bellingshausen Sea King George Island Stranger Point ENVELOPE(-58.618,-58.618,-62.262,-62.262) Marine Ecology Progress Series 268 293 300 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
The response of altered sex ratio in southern elephant seals due to environmental stress was analysed. Data were collected at King George Island from 1980 to 1994. Significant retreats in the ice cover during El Niño events strongly suggest environmental stress during this period along the Bellingshausen Sea, a zone where female elephant seals from King George Island feed during their pregnancy. Randomly chosen weaning elephant seal pups (n = 1178) were sexed at Stranger Point (King George Island, 62°14¹S, 58°30¹W) over 5 km of beach from 1985 to 1994. Adult sex ratio was also determined annually from 1980 to 1994 as the ratio between maximum number of bulls and females on land. The theoretical pup sex ratio was assumed as 1:1 according to background information. Adult sex ratio was calculated as 1:6. To define the occurrence of El Niño Southern Oscillation (ENSO) during the study period, a sea surface temperature (SST) index called ŒNiño 3.4¹ for the region 5°N to 5°S, 120°E to 170°W was considered. Monthly SST anomalies were obtained from the Climate Prediction Center (CPC, NOAA). To provide an annual index of anomaly strength (IAS), the monthly adjusted oscillation index climatology (AOIC) was averaged. Accumulated values during the whole study period showed that during El Niño years (1987, 1991, 1992) the proportion of pups was significantly biased in favour of females (p < 0.01). During normal years (1986, 1990, 1993, 1994) and La Niña years (1985, 1988, 1989), accumulative values showed a greater proportion of male pups to females (p < 0.05). Using the 1:1 hypothesis, we found during El Niño years a 9% reduction in the male segment, whereas in non-El Niño years a recovery of 7% was observed (3% during normal years and 4% during La Niña years. To see the influence of accumulative values of pup sex ratio in adult sex ratio, a theoretical adult proportion was calculated as 1:6. To test this hypothesis, information on adult sex ratio taken from King George Island between 1980 and 1994 (n = 14 yr) was ... |
format |
Article in Journal/Newspaper |
author |
Vergani, Daniel F. Stanganelli, Zulma B. Bilenca, David |
spellingShingle |
Vergani, Daniel F. Stanganelli, Zulma B. Bilenca, David Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island |
author_facet |
Vergani, Daniel F. Stanganelli, Zulma B. Bilenca, David |
author_sort |
Vergani, Daniel F. |
title |
Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island |
title_short |
Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island |
title_full |
Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island |
title_fullStr |
Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island |
title_full_unstemmed |
Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island |
title_sort |
effects of el niño and la niña events on the sex ratio of southern elephant seals at king george island |
publisher |
Inter-Research |
publishDate |
2004 |
url |
https://oceanrep.geomar.de/id/eprint/53772/ https://oceanrep.geomar.de/id/eprint/53772/1/4443.pdf https://doi.org/10.3354/meps268293 |
long_lat |
ENVELOPE(-58.618,-58.618,-62.262,-62.262) |
geographic |
Bellingshausen Sea King George Island Stranger Point |
geographic_facet |
Bellingshausen Sea King George Island Stranger Point |
genre |
Bellingshausen Sea Elephant Seal Elephant Seals King George Island Southern Elephant Seals |
genre_facet |
Bellingshausen Sea Elephant Seal Elephant Seals King George Island Southern Elephant Seals |
op_relation |
https://oceanrep.geomar.de/id/eprint/53772/1/4443.pdf Vergani, D. F., Stanganelli, Z. B. and Bilenca, D. (2004) Effects of El Niño and La Niña events on the sex ratio of southern elephant seals at King George Island. Open Access Marine Ecology Progress Series, 268 . pp. 293-300. DOI 10.3354/meps268293 <https://doi.org/10.3354/meps268293>. doi:10.3354/meps268293 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.3354/meps268293 |
container_title |
Marine Ecology Progress Series |
container_volume |
268 |
container_start_page |
293 |
op_container_end_page |
300 |
_version_ |
1766374310048432128 |