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Comparison of southern elephant seal populations, and observations of a population on a demographic knife-edge

McMahon, Clive R., Hindell, Mark A., Burton, Harry R. and Bester, Marthan N. (2005). Comparison of southern elephant seal populations, and observations of a population on a demographic knife-edge. Marine Ecology: Progress Series,288:273-283.

Document type: Journal Article
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IRMA ID 79264438xPUB38
Title Comparison of southern elephant seal populations, and observations of a population on a demographic knife-edge
Author McMahon, Clive R.
Hindell, Mark A.
Burton, Harry R.
Bester, Marthan N.
Journal Name Marine Ecology: Progress Series
Publication Date 2005
Volume Number 288
ISSN 0171-8630   (check CDU catalogue open catalogue search in new window)
Start Page 273
End Page 283
Total Pages 11
Place of Publication Oldendorf, Germany
Publisher Inter-Research
Field of Research 0406 - Physical Geography and Environmental Geoscience
0602 - Ecology
HERDC Category C1 - Journal Article (DEST)
Abstract The dynamics of animal populations are determined by several key demographic parameters, which vary over time with resultant changes in the status of the population. When managing declining populations, the identificationof the parameters that drive such change are a high priority, but are rarely achieved for large and long-lived species. Southern elephant seal populations in the South Indian and South Pacific oceans have decreased by as much as 50 % during the past 50 yr. The reasons for these decreases remained unknown. This study used a projected stochastic Leslie-matrix model based on long-term demographic data to examine the potential role of several life-history parameters in contributing to the declines. The models simulated the observed population trends that were independently derived from annual abundance surveys. Small changes in survival and fecundity had dramatic effects on population growth rates. At Macquarie Island for example, a small change (ca. 5%) in survival and fecundity rates resulted in the population reverting from a decreasing one to a population that increased. The vital rates that had the greatest impact on fitness were, in order of importance: (1) juvenile survival, (2) adult survival, (3) adult fecundity and (4) juvenile fecundity. Population viability analysis (PVA) for each of the 2 decreasing populations revealed that there was a high probability of the Marion Island population becoming extinct within the next 150 yr, while the probability of extinction at Macquarie Island was low. The estimated mean times to extinction for each population was 134 yr (95% confidence intervals: 105 to 332 yr) at Marion Island and 564 yr at Macquarie Island (the earliest time to extinction was 307 yr).
Keywords Elasticity
Population fitness
Population trajectories
Vital rates
DOI http://dx.doi.org/10.3354/meps288273   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
Additional Notes Copyright by Inter Research - McMahon, Clive R., Hindell, Mark A., Burton, Harry R. Bester, Marthán N. - Comparison of southern elephant seal populations, and observations of a population on a demographic knife-edge, MEPS 288:273-283 (2005) http://www.int-res.com/abstracts/meps/v288/p273-283/


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