Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals.
BACKGROUND: Determining the relative contribution of intrinsic and extrinsic factors to fluctuations in population size, trends and demographic composition is analytically complex. It is often only possible to examine the combined effects of these factors through measurements made over long periods,...
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2007
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Online Access: | http://hdl.handle.net/11343/264064 |
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ftumelbourne:oai:jupiter.its.unimelb.edu.au:11343/264064 2024-06-02T08:06:02+00:00 Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. de Little, SC Bradshaw, CJA McMahon, CR Hindell, MA 2007-03-27 http://hdl.handle.net/11343/264064 eng eng Springer Science and Business Media LLC issn:1472-6785 doi:10.1186/1472-6785-7-3 pii: 1472-6785-7-3 de Little, S. C., Bradshaw, C. J. A., McMahon, C. R. & Hindell, M. A. (2007). Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. BMC Ecol, 7 (1), pp.3-. https://doi.org/10.1186/1472-6785-7-3. 1472-6785 http://hdl.handle.net/11343/264064 CC BY https://creativecommons.org/licenses/by/4.0 Journal Article 2007 ftumelbourne https://doi.org/10.1186/1472-6785-7-3 2024-05-06T11:56:18Z BACKGROUND: Determining the relative contribution of intrinsic and extrinsic factors to fluctuations in population size, trends and demographic composition is analytically complex. It is often only possible to examine the combined effects of these factors through measurements made over long periods, spanning an array of population densities or levels of food availability. Using age-structured mark-recapture models and datasets spanning five decades (1950-1999), and two periods of differing relative population density, we estimated age-specific probabilities of survival and examined the combined effects of population density and environmental conditions on juvenile survival of southern elephant seals at Macquarie Island. RESULTS: First-year survival decreased with density during the period of highest population size, and survival increased during years when the Southern Oscillation Index (SOI) anomaly (deviation from a 50-year mean) during the mother's previous foraging trip to sea was positive (i.e., El Niño). However, when environmental stochasticity and density were considered together, the effect of density on first-year survival effectively disappeared. Ignoring density effects also leads to models placing too much emphasis on the environmental conditions prevailing during the naïve pup's first year at sea. CONCLUSION: Our analyses revealed that both the state of the environment and population density combine to modify juvenile survival, but that the degree to which these processes contributed to the variation observed was interactive and complex. This underlines the importance of evaluating the relative contribution of both the intrinsic and extrinsic factors that regulate animal populations because false conclusions regarding the importance of population regulation may be reached if they are examined in isolation. Article in Journal/Newspaper Elephant Seals Macquarie Island Southern Elephant Seals The University of Melbourne: Digital Repository Soi ENVELOPE(30.704,30.704,66.481,66.481) BMC Ecology 7 1 |
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Open Polar |
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The University of Melbourne: Digital Repository |
op_collection_id |
ftumelbourne |
language |
English |
description |
BACKGROUND: Determining the relative contribution of intrinsic and extrinsic factors to fluctuations in population size, trends and demographic composition is analytically complex. It is often only possible to examine the combined effects of these factors through measurements made over long periods, spanning an array of population densities or levels of food availability. Using age-structured mark-recapture models and datasets spanning five decades (1950-1999), and two periods of differing relative population density, we estimated age-specific probabilities of survival and examined the combined effects of population density and environmental conditions on juvenile survival of southern elephant seals at Macquarie Island. RESULTS: First-year survival decreased with density during the period of highest population size, and survival increased during years when the Southern Oscillation Index (SOI) anomaly (deviation from a 50-year mean) during the mother's previous foraging trip to sea was positive (i.e., El Niño). However, when environmental stochasticity and density were considered together, the effect of density on first-year survival effectively disappeared. Ignoring density effects also leads to models placing too much emphasis on the environmental conditions prevailing during the naïve pup's first year at sea. CONCLUSION: Our analyses revealed that both the state of the environment and population density combine to modify juvenile survival, but that the degree to which these processes contributed to the variation observed was interactive and complex. This underlines the importance of evaluating the relative contribution of both the intrinsic and extrinsic factors that regulate animal populations because false conclusions regarding the importance of population regulation may be reached if they are examined in isolation. |
format |
Article in Journal/Newspaper |
author |
de Little, SC Bradshaw, CJA McMahon, CR Hindell, MA |
spellingShingle |
de Little, SC Bradshaw, CJA McMahon, CR Hindell, MA Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. |
author_facet |
de Little, SC Bradshaw, CJA McMahon, CR Hindell, MA |
author_sort |
de Little, SC |
title |
Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. |
title_short |
Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. |
title_full |
Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. |
title_fullStr |
Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. |
title_full_unstemmed |
Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. |
title_sort |
complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. |
publisher |
Springer Science and Business Media LLC |
publishDate |
2007 |
url |
http://hdl.handle.net/11343/264064 |
long_lat |
ENVELOPE(30.704,30.704,66.481,66.481) |
geographic |
Soi |
geographic_facet |
Soi |
genre |
Elephant Seals Macquarie Island Southern Elephant Seals |
genre_facet |
Elephant Seals Macquarie Island Southern Elephant Seals |
op_relation |
issn:1472-6785 doi:10.1186/1472-6785-7-3 pii: 1472-6785-7-3 de Little, S. C., Bradshaw, C. J. A., McMahon, C. R. & Hindell, M. A. (2007). Complex interplay between intrinsic and extrinsic drivers of long-term survival trends in southern elephant seals. BMC Ecol, 7 (1), pp.3-. https://doi.org/10.1186/1472-6785-7-3. 1472-6785 http://hdl.handle.net/11343/264064 |
op_rights |
CC BY https://creativecommons.org/licenses/by/4.0 |
op_doi |
https://doi.org/10.1186/1472-6785-7-3 |
container_title |
BMC Ecology |
container_volume |
7 |
container_issue |
1 |
_version_ |
1800750920623980544 |