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The sun, moon, wind, and biological imperative – shaping contrasting wintertime migration and foraging strategies of adult male and female Northern Fur Seals (Callorhinus ursinus)

Citation

Sterling, JT and Springer, AM and Iverson, SJ and Johnson, SP and Pelland, NA and Johnson, DS and Lea, M-A and Bond, NA, The sun, moon, wind, and biological imperative - shaping contrasting wintertime migration and foraging strategies of adult male and female Northern Fur Seals (Callorhinus ursinus), PLoS One, 9, (4) Article e93068. ISSN 1932-6203 (2014) [Refereed Article]


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Copyright 2014 the Authors-this article is distributed under a Creative Commons Dedication (CC0 1.0)-free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.

DOI: doi:10.1371/journal.pone.0093068

Abstract

Adult male and female northern fur seals (Callorhinus ursinus) are sexually segregated in different regions of the North Pacific Ocean and Bering Sea during their winter migration. Explanations for this involve interplay between physiology, predator-prey dynamics, and ecosystem characteristics, however possible mechanisms lack empirical support. To investigate factors influencing the winter ecology of both sexes, we deployed five satellite-linked conductivity, temperature, and depth data loggers on adult males, and six satellite-linked depth data loggers and four satellite transmitters on adult females from St. Paul Island (Bering Sea, Alaska, USA) in October 2009. Males and females migrated to different regions of the North Pacific Ocean: males wintered in the Bering Sea and northern North Pacific Ocean, while females migrated to the Gulf of Alaska and California Current. Horizontal and vertical movement behaviors of both sexes were influenced by wind speed, season, light (sun and moon), and the ecosystem they occupied, although the expression of the behaviors differed between sexes. Male dive depths were aligned with the depth of the mixed layer during daylight periods and we suspect this was the case for females upon their arrival to the California Current. We suggest that females, because of their smaller size and physiological limitations, must avoid severe winters typical of the northern North Pacific Ocean and Bering Sea and migrate long distances to areas of more benign environmental conditions and where prey is shallower and more accessible. In contrast, males can better tolerate often extreme winter ocean conditions and exploit prey at depth because of their greater size and physiological capabilities. We believe these contrasting winter behaviors 1) are a consequence of evolutionary selection for large size in males, important to the acquisition and defense of territories against rivals during the breeding season, and 2) ease environmental/physiological constraints imposed on smaller females

Item Details

Item Type:Refereed Article
Keywords:migration, mixed layer, current, North Pacific, diving
Research Division:Environmental Sciences
Research Group:Environmental Science and Management
Research Field:Wildlife and Habitat Management
Objective Division:Environment
Objective Group:Flora, Fauna and Biodiversity
Objective Field:Marine Flora, Fauna and Biodiversity
Author:Lea, M-A (Associate Professor Mary-Anne Lea)
ID Code:91535
Year Published:2014
Web of Science® Times Cited:10
Deposited By:IMAS Research and Education Centre
Deposited On:2014-05-21
Last Modified:2017-10-31
Downloads:208 View Download Statistics

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