Do southern elephant seals show density dependence in fecundity?
Here we provide an alternative interpretation to that of Pistorius et al. (2001), concerning density-dependent increases in fecundity resulting in population regulation of the southern elephant seal population at Marion Island. We do not contradict the findings of Pistorius et al. (2001), because it...
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ftunivadelaidedl:oai:digital.library.adelaide.edu.au:2440/48187 2023-05-15T16:05:23+02:00 Do southern elephant seals show density dependence in fecundity? Bradshaw, C. McMahon, C. Hindell, M. Pistorius, P. Bester, M. 2002 http://hdl.handle.net/2440/48187 https://doi.org/10.1007/s00300-002-0396-5 en eng Springer-Verlag Polar Biology, 2002; 25(9):650-655 0722-4060 1432-2056 http://hdl.handle.net/2440/48187 doi:10.1007/s00300-002-0396-5 Bradshaw, C. [0000-0002-5328-7741] http://www.springerlink.com/content/l00vgtlhr3qp/?p=9ccde29b656e43d28bdb57047849f0d2&pi=0 Journal article 2002 ftunivadelaidedl https://doi.org/10.1007/s00300-002-0396-5 2023-02-06T06:59:42Z Here we provide an alternative interpretation to that of Pistorius et al. (2001), concerning density-dependent increases in fecundity resulting in population regulation of the southern elephant seal population at Marion Island. We do not contradict the findings of Pistorius et al. (2001), because it does appear: (1) that a change in fecundity has been observed, and (2) that some factor related to food supply is the most likely cause for an observed population decline and increase in reproductive performance. The main observation leading to the interpretation of density-dependent feedback in the population of southern elephant seals at Marion Island (one of the Prince Edward Islands) is that there has been a reduction in the population's rate of decline in recent years (reported by Pistorius et al. (1999b)), and that this could have resulted from a per capita increase in food availability. However, because rates of population change are rarely linearly constant, changes in population size should be expressed on a logarithmic, rather than a linear scale, as used by Pistorius et al. (1999b). Re-plotting the linear values of Pistorius et al. (1999b) on the natural logarithmic scale gave no clear change in the rate of population decline; therefore, we conclude that the rate of population change (decline) has remained constant from 1986 to 1997 (r=-0.0439). The Marion Island population is part of the larger Kerguelen population, and there might be considerable overlap in the foraging areas, and possibly prey, exploited by elephant seals from all sub-populations within this larger population. Changes in the number of intra-specific resource competitors at Marion Island are therefore unlikely to alter per capita food availability since the Marion population constitutes approximately 1% of the total Kerguelen population. We propose an alternative hypothesis that the present data support a mechanism driving the proposed increase in per capita food supply through changes in either: (1) inter-specific food competition, (2) ... Article in Journal/Newspaper Elephant Seal Elephant Seals Marion Island Polar Biology Prince Edward Islands Southern Elephant Seal Southern Elephant Seals The University of Adelaide: Digital Library Kerguelen Polar Biology 25 9 650 655 |
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Open Polar |
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The University of Adelaide: Digital Library |
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ftunivadelaidedl |
language |
English |
description |
Here we provide an alternative interpretation to that of Pistorius et al. (2001), concerning density-dependent increases in fecundity resulting in population regulation of the southern elephant seal population at Marion Island. We do not contradict the findings of Pistorius et al. (2001), because it does appear: (1) that a change in fecundity has been observed, and (2) that some factor related to food supply is the most likely cause for an observed population decline and increase in reproductive performance. The main observation leading to the interpretation of density-dependent feedback in the population of southern elephant seals at Marion Island (one of the Prince Edward Islands) is that there has been a reduction in the population's rate of decline in recent years (reported by Pistorius et al. (1999b)), and that this could have resulted from a per capita increase in food availability. However, because rates of population change are rarely linearly constant, changes in population size should be expressed on a logarithmic, rather than a linear scale, as used by Pistorius et al. (1999b). Re-plotting the linear values of Pistorius et al. (1999b) on the natural logarithmic scale gave no clear change in the rate of population decline; therefore, we conclude that the rate of population change (decline) has remained constant from 1986 to 1997 (r=-0.0439). The Marion Island population is part of the larger Kerguelen population, and there might be considerable overlap in the foraging areas, and possibly prey, exploited by elephant seals from all sub-populations within this larger population. Changes in the number of intra-specific resource competitors at Marion Island are therefore unlikely to alter per capita food availability since the Marion population constitutes approximately 1% of the total Kerguelen population. We propose an alternative hypothesis that the present data support a mechanism driving the proposed increase in per capita food supply through changes in either: (1) inter-specific food competition, (2) ... |
format |
Article in Journal/Newspaper |
author |
Bradshaw, C. McMahon, C. Hindell, M. Pistorius, P. Bester, M. |
spellingShingle |
Bradshaw, C. McMahon, C. Hindell, M. Pistorius, P. Bester, M. Do southern elephant seals show density dependence in fecundity? |
author_facet |
Bradshaw, C. McMahon, C. Hindell, M. Pistorius, P. Bester, M. |
author_sort |
Bradshaw, C. |
title |
Do southern elephant seals show density dependence in fecundity? |
title_short |
Do southern elephant seals show density dependence in fecundity? |
title_full |
Do southern elephant seals show density dependence in fecundity? |
title_fullStr |
Do southern elephant seals show density dependence in fecundity? |
title_full_unstemmed |
Do southern elephant seals show density dependence in fecundity? |
title_sort |
do southern elephant seals show density dependence in fecundity? |
publisher |
Springer-Verlag |
publishDate |
2002 |
url |
http://hdl.handle.net/2440/48187 https://doi.org/10.1007/s00300-002-0396-5 |
geographic |
Kerguelen |
geographic_facet |
Kerguelen |
genre |
Elephant Seal Elephant Seals Marion Island Polar Biology Prince Edward Islands Southern Elephant Seal Southern Elephant Seals |
genre_facet |
Elephant Seal Elephant Seals Marion Island Polar Biology Prince Edward Islands Southern Elephant Seal Southern Elephant Seals |
op_source |
http://www.springerlink.com/content/l00vgtlhr3qp/?p=9ccde29b656e43d28bdb57047849f0d2&pi=0 |
op_relation |
Polar Biology, 2002; 25(9):650-655 0722-4060 1432-2056 http://hdl.handle.net/2440/48187 doi:10.1007/s00300-002-0396-5 Bradshaw, C. [0000-0002-5328-7741] |
op_doi |
https://doi.org/10.1007/s00300-002-0396-5 |
container_title |
Polar Biology |
container_volume |
25 |
container_issue |
9 |
container_start_page |
650 |
op_container_end_page |
655 |
_version_ |
1766401283363700736 |