Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa
The Bird Island in Algoa Bay supports a breeding colony of South African (Cape) fur seals, Arctocephalus pusillus pusillus (n=1000-3000) on Black Rocks which is the easternmost extreme of their breeding range and so it is likely to be the most environmentally marginal of the existing fur seal coloni...
Published in: | South African Geographical Journal |
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Language: | English |
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Online Access: | https://researchers.mq.edu.au/en/publications/83551bd8-8554-4ac6-8fcc-90a1dba9bf9e https://doi.org/10.1080/03736245.2012.667626 http://www.scopus.com/inward/record.url?scp=84861557667&partnerID=8YFLogxK |
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ftmacquarieunicr:oai:https://researchers.mq.edu.au:publications/83551bd8-8554-4ac6-8fcc-90a1dba9bf9e 2023-05-15T15:44:38+02:00 Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa Stewardson, Carolyn L. Prvan, Tania Ritchie, Raymond J. 2012-06-01 https://researchers.mq.edu.au/en/publications/83551bd8-8554-4ac6-8fcc-90a1dba9bf9e https://doi.org/10.1080/03736245.2012.667626 http://www.scopus.com/inward/record.url?scp=84861557667&partnerID=8YFLogxK eng eng info:eu-repo/semantics/closedAccess Stewardson , C L , Prvan , T & Ritchie , R J 2012 , ' Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa ' , South African Geographical Journal , vol. 94 , no. 1 , pp. 22-45 . https://doi.org/10.1080/03736245.2012.667626 article 2012 ftmacquarieunicr https://doi.org/10.1080/03736245.2012.667626 2022-11-06T06:35:30Z The Bird Island in Algoa Bay supports a breeding colony of South African (Cape) fur seals, Arctocephalus pusillus pusillus (n=1000-3000) on Black Rocks which is the easternmost extreme of their breeding range and so it is likely to be the most environmentally marginal of the existing fur seal colonies. Conditions on Bird Island for seal pups are not as benign as they might first appear, particularly with regard to air temperatures. Climatic conditions on Bird Island were recorded in 1993-1995 and are compared to the conditions at Port Elizabeth Airport 63km W-SW from the Bird Islands. Daily maximum and minimum temperatures, sea surface temperatures (SSTs) and rainfall were compared to concurrent Port Elizabeth data. Wind speeds and directions and sea swell heights at Bird Island were also recorded. Air temperatures ranged from 9°C to 33°C, SSTs ranged from 12°C to 23°C, total annual rainfall was ≈600mm and there were typically relatively strong winds (13-15 knots/7-8ms -1 ) predominantly W-SW and E-NE. Intermittent periods of calm hot weather during summer pupping season would lead to potentially lethal hyperthermia (heat stroke). In 1993-1995, about 50% of summer days were potentially lethal to seal pups in the open by hyperthermia if the wind speed is near zero. Eddying of the Agulhas Current and strong winds leads to irregular favourable small-scale upwelling events, but incursions of warm water in hot still weather occurred in January-March 1993 and November-December 1993 and likely lead to starvation of some pups as well as endangering seal pups by hyperthermia. Detailed climate data are usually not available for seal colony sites, but we found good correlations between the offshore Bird Islands and climate data collected from the nearest permanent weather station (Port Elizabeth Airport) making it possible to infer long-term changes in conditions on Bird Island based upon Port Elizabeth data. We show that modest (2°C) increases in average summer temperatures would greatly increase the number of potentially ... Article in Journal/Newspaper Bird Island Black Rocks Macquarie University Research Portal Bird Island ENVELOPE(-38.060,-38.060,-54.004,-54.004) South African Geographical Journal 94 1 22 45 |
institution |
Open Polar |
collection |
Macquarie University Research Portal |
op_collection_id |
ftmacquarieunicr |
language |
English |
description |
The Bird Island in Algoa Bay supports a breeding colony of South African (Cape) fur seals, Arctocephalus pusillus pusillus (n=1000-3000) on Black Rocks which is the easternmost extreme of their breeding range and so it is likely to be the most environmentally marginal of the existing fur seal colonies. Conditions on Bird Island for seal pups are not as benign as they might first appear, particularly with regard to air temperatures. Climatic conditions on Bird Island were recorded in 1993-1995 and are compared to the conditions at Port Elizabeth Airport 63km W-SW from the Bird Islands. Daily maximum and minimum temperatures, sea surface temperatures (SSTs) and rainfall were compared to concurrent Port Elizabeth data. Wind speeds and directions and sea swell heights at Bird Island were also recorded. Air temperatures ranged from 9°C to 33°C, SSTs ranged from 12°C to 23°C, total annual rainfall was ≈600mm and there were typically relatively strong winds (13-15 knots/7-8ms -1 ) predominantly W-SW and E-NE. Intermittent periods of calm hot weather during summer pupping season would lead to potentially lethal hyperthermia (heat stroke). In 1993-1995, about 50% of summer days were potentially lethal to seal pups in the open by hyperthermia if the wind speed is near zero. Eddying of the Agulhas Current and strong winds leads to irregular favourable small-scale upwelling events, but incursions of warm water in hot still weather occurred in January-March 1993 and November-December 1993 and likely lead to starvation of some pups as well as endangering seal pups by hyperthermia. Detailed climate data are usually not available for seal colony sites, but we found good correlations between the offshore Bird Islands and climate data collected from the nearest permanent weather station (Port Elizabeth Airport) making it possible to infer long-term changes in conditions on Bird Island based upon Port Elizabeth data. We show that modest (2°C) increases in average summer temperatures would greatly increase the number of potentially ... |
format |
Article in Journal/Newspaper |
author |
Stewardson, Carolyn L. Prvan, Tania Ritchie, Raymond J. |
spellingShingle |
Stewardson, Carolyn L. Prvan, Tania Ritchie, Raymond J. Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa |
author_facet |
Stewardson, Carolyn L. Prvan, Tania Ritchie, Raymond J. |
author_sort |
Stewardson, Carolyn L. |
title |
Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa |
title_short |
Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa |
title_full |
Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa |
title_fullStr |
Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa |
title_full_unstemmed |
Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa |
title_sort |
climate of a south african fur seal (arctocephalus pusillus pusillus) breeding island off the south-east coast of south africa |
publishDate |
2012 |
url |
https://researchers.mq.edu.au/en/publications/83551bd8-8554-4ac6-8fcc-90a1dba9bf9e https://doi.org/10.1080/03736245.2012.667626 http://www.scopus.com/inward/record.url?scp=84861557667&partnerID=8YFLogxK |
long_lat |
ENVELOPE(-38.060,-38.060,-54.004,-54.004) |
geographic |
Bird Island |
geographic_facet |
Bird Island |
genre |
Bird Island Black Rocks |
genre_facet |
Bird Island Black Rocks |
op_source |
Stewardson , C L , Prvan , T & Ritchie , R J 2012 , ' Climate of a South African fur seal (Arctocephalus pusillus pusillus) breeding island off the south-east coast of South Africa ' , South African Geographical Journal , vol. 94 , no. 1 , pp. 22-45 . https://doi.org/10.1080/03736245.2012.667626 |
op_rights |
info:eu-repo/semantics/closedAccess |
op_doi |
https://doi.org/10.1080/03736245.2012.667626 |
container_title |
South African Geographical Journal |
container_volume |
94 |
container_issue |
1 |
container_start_page |
22 |
op_container_end_page |
45 |
_version_ |
1766379021457686528 |