An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals
Much of the existing literature that evaluates the roles of density‐dependent and density‐independent factors on population dynamics has been called into question in recent years because measurement errors were not properly dealt with in analyses. Using state–space models to account for measurement...
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crwiley:10.1890/08-0971.1 2024-09-15T17:43:34+00:00 An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals Rotella, Jay J. Link, William A. Nichols, James D. Hadley, Gillian L. Garrott, Robert A. Proffitt, Kelly M. 2009 http://dx.doi.org/10.1890/08-0971.1 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1890%2F08-0971.1 https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/08-0971.1 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Ecology volume 90, issue 4, page 975-984 ISSN 0012-9658 1939-9170 journal-article 2009 crwiley https://doi.org/10.1890/08-0971.1 2024-08-15T04:20:38Z Much of the existing literature that evaluates the roles of density‐dependent and density‐independent factors on population dynamics has been called into question in recent years because measurement errors were not properly dealt with in analyses. Using state–space models to account for measurement errors, we evaluated a set of competing models for a 22‐year time series of mark–resight estimates of abundance for a breeding population of female Weddell seals ( Leptonychotes weddellii ) studied in Erebus Bay, Antarctica. We tested for evidence of direct density dependence in growth rates and evaluated whether equilibrium population size was related to seasonal sea‐ice extent and the Southern Oscillation Index (SOI). We found strong evidence of negative density dependence in annual growth rates for a population whose estimated size ranged from 438 to 623 females during the study. Based on Bayes factors, a density‐dependence‐only model was favored over models that also included environmental covariates. According to the favored model, the population had a stationary distribution with a mean of 497 females (SD = 60.5), an expected growth rate of 1.10 (95% credible interval = 1.08–1.15) when population size was 441 females, and a rate of 0.90 (95% credible interval = 0.87–0.93) for a population of 553 females. A model including effects of SOI did receive some support and indicated a positive relationship between SOI and population size. However, effects of SOI were not large, and including the effect did not greatly reduce our estimate of process variation. We speculate that direct density dependence occurred because rates of adult survival, breeding, and temporary emigration were affected by limitations on per capita food resources and space for parturition and pup‐rearing. To improve understanding of the relative roles of various demographic components and their associated vital rates to population growth rate, mark–recapture methods can be applied that incorporate both environmental covariates and the seal ... Article in Journal/Newspaper Antarc* Antarctica Sea ice Weddell Seals Wiley Online Library Ecology 90 4 975 984 |
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Open Polar |
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Wiley Online Library |
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crwiley |
language |
English |
description |
Much of the existing literature that evaluates the roles of density‐dependent and density‐independent factors on population dynamics has been called into question in recent years because measurement errors were not properly dealt with in analyses. Using state–space models to account for measurement errors, we evaluated a set of competing models for a 22‐year time series of mark–resight estimates of abundance for a breeding population of female Weddell seals ( Leptonychotes weddellii ) studied in Erebus Bay, Antarctica. We tested for evidence of direct density dependence in growth rates and evaluated whether equilibrium population size was related to seasonal sea‐ice extent and the Southern Oscillation Index (SOI). We found strong evidence of negative density dependence in annual growth rates for a population whose estimated size ranged from 438 to 623 females during the study. Based on Bayes factors, a density‐dependence‐only model was favored over models that also included environmental covariates. According to the favored model, the population had a stationary distribution with a mean of 497 females (SD = 60.5), an expected growth rate of 1.10 (95% credible interval = 1.08–1.15) when population size was 441 females, and a rate of 0.90 (95% credible interval = 0.87–0.93) for a population of 553 females. A model including effects of SOI did receive some support and indicated a positive relationship between SOI and population size. However, effects of SOI were not large, and including the effect did not greatly reduce our estimate of process variation. We speculate that direct density dependence occurred because rates of adult survival, breeding, and temporary emigration were affected by limitations on per capita food resources and space for parturition and pup‐rearing. To improve understanding of the relative roles of various demographic components and their associated vital rates to population growth rate, mark–recapture methods can be applied that incorporate both environmental covariates and the seal ... |
format |
Article in Journal/Newspaper |
author |
Rotella, Jay J. Link, William A. Nichols, James D. Hadley, Gillian L. Garrott, Robert A. Proffitt, Kelly M. |
spellingShingle |
Rotella, Jay J. Link, William A. Nichols, James D. Hadley, Gillian L. Garrott, Robert A. Proffitt, Kelly M. An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals |
author_facet |
Rotella, Jay J. Link, William A. Nichols, James D. Hadley, Gillian L. Garrott, Robert A. Proffitt, Kelly M. |
author_sort |
Rotella, Jay J. |
title |
An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals |
title_short |
An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals |
title_full |
An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals |
title_fullStr |
An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals |
title_full_unstemmed |
An evaluation of density‐dependent and density‐independent influences on population growth rates in Weddell seals |
title_sort |
evaluation of density‐dependent and density‐independent influences on population growth rates in weddell seals |
publisher |
Wiley |
publishDate |
2009 |
url |
http://dx.doi.org/10.1890/08-0971.1 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1890%2F08-0971.1 https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/08-0971.1 |
genre |
Antarc* Antarctica Sea ice Weddell Seals |
genre_facet |
Antarc* Antarctica Sea ice Weddell Seals |
op_source |
Ecology volume 90, issue 4, page 975-984 ISSN 0012-9658 1939-9170 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1890/08-0971.1 |
container_title |
Ecology |
container_volume |
90 |
container_issue |
4 |
container_start_page |
975 |
op_container_end_page |
984 |
_version_ |
1810490598199656448 |