Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island
Abstract The population of Steller sea lions (SSLs) on Tuleny Island has been increasing continuously since the 1980s. However, the reasons for this increase have remained unknown. In this study, we investigated whether changes in sea ice distribution affected population dynamics on Tuleny Island by...
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crwiley:10.1111/1440-1703.12043 2024-06-02T08:14:12+00:00 Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island Mizuguchi, Daisuke Kato, Keiko Okamoto, Suguru Hattori, Kaoru Sakurai, Yasunori 2019 http://dx.doi.org/10.1111/1440-1703.12043 https://onlinelibrary.wiley.com/doi/pdf/10.1111/1440-1703.12043 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/1440-1703.12043 en eng Wiley http://creativecommons.org/licenses/by/4.0/ Ecological Research volume 35, issue 1, page 113-122 ISSN 0912-3814 1440-1703 journal-article 2019 crwiley https://doi.org/10.1111/1440-1703.12043 2024-05-03T11:54:01Z Abstract The population of Steller sea lions (SSLs) on Tuleny Island has been increasing continuously since the 1980s. However, the reasons for this increase have remained unknown. In this study, we investigated whether changes in sea ice distribution affected population dynamics on Tuleny Island by applying a Gompertz density‐dependent model in a state‐space framework with a time‐varying coefficient. We compared results from the time‐varying coefficient model with those from two other models that assumed time‐constant effects and no effect of sea ice. For both SSL pups and non‐pups, only the time‐varying coefficient model predicted a significant effect from the timing of sea ice breakup. The SSL population was larger when the sea ice broke up earlier. The sea ice effect was larger at the start of the study period and became insignificant in the late 1980s. Thus, our results suggest that the increase in SSL population on Tuleny Island during the first 20 years could be partly explained by earlier sea ice breakup, which promoted immigration from other rookeries. Because SSLs exhibit strong site‐fidelity as the habituation effect, individuals that visited once may have repeatedly returned to visit and breed on the island, regardless of the sea ice conditions in later years. This may explain why the sea ice effect was only significant in the first years of population increase. Negative density dependence was also only predicted by the time‐varying coefficient model. Adding the time‐varying coefficient to modeling analysis could simultaneously improve predictions of environmental effects and estimations of density dependence. Article in Journal/Newspaper Sea ice Wiley Online Library Ecological Research 35 1 113 122 |
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Open Polar |
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Wiley Online Library |
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English |
description |
Abstract The population of Steller sea lions (SSLs) on Tuleny Island has been increasing continuously since the 1980s. However, the reasons for this increase have remained unknown. In this study, we investigated whether changes in sea ice distribution affected population dynamics on Tuleny Island by applying a Gompertz density‐dependent model in a state‐space framework with a time‐varying coefficient. We compared results from the time‐varying coefficient model with those from two other models that assumed time‐constant effects and no effect of sea ice. For both SSL pups and non‐pups, only the time‐varying coefficient model predicted a significant effect from the timing of sea ice breakup. The SSL population was larger when the sea ice broke up earlier. The sea ice effect was larger at the start of the study period and became insignificant in the late 1980s. Thus, our results suggest that the increase in SSL population on Tuleny Island during the first 20 years could be partly explained by earlier sea ice breakup, which promoted immigration from other rookeries. Because SSLs exhibit strong site‐fidelity as the habituation effect, individuals that visited once may have repeatedly returned to visit and breed on the island, regardless of the sea ice conditions in later years. This may explain why the sea ice effect was only significant in the first years of population increase. Negative density dependence was also only predicted by the time‐varying coefficient model. Adding the time‐varying coefficient to modeling analysis could simultaneously improve predictions of environmental effects and estimations of density dependence. |
format |
Article in Journal/Newspaper |
author |
Mizuguchi, Daisuke Kato, Keiko Okamoto, Suguru Hattori, Kaoru Sakurai, Yasunori |
spellingShingle |
Mizuguchi, Daisuke Kato, Keiko Okamoto, Suguru Hattori, Kaoru Sakurai, Yasunori Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island |
author_facet |
Mizuguchi, Daisuke Kato, Keiko Okamoto, Suguru Hattori, Kaoru Sakurai, Yasunori |
author_sort |
Mizuguchi, Daisuke |
title |
Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island |
title_short |
Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island |
title_full |
Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island |
title_fullStr |
Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island |
title_full_unstemmed |
Time‐varying effect of sea ice on the population dynamics of Steller sea lions ( Eumetopias jubatus) on Tuleny Island |
title_sort |
time‐varying effect of sea ice on the population dynamics of steller sea lions ( eumetopias jubatus) on tuleny island |
publisher |
Wiley |
publishDate |
2019 |
url |
http://dx.doi.org/10.1111/1440-1703.12043 https://onlinelibrary.wiley.com/doi/pdf/10.1111/1440-1703.12043 https://onlinelibrary.wiley.com/doi/full-xml/10.1111/1440-1703.12043 |
genre |
Sea ice |
genre_facet |
Sea ice |
op_source |
Ecological Research volume 35, issue 1, page 113-122 ISSN 0912-3814 1440-1703 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1111/1440-1703.12043 |
container_title |
Ecological Research |
container_volume |
35 |
container_issue |
1 |
container_start_page |
113 |
op_container_end_page |
122 |
_version_ |
1800737937118199808 |