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Marine Ecology Progress Series

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MEPS 407:293-302 (2010)  -  DOI:

Divergent movements of walrus and sea ice in the northern Bering Sea

Chadwick V. Jay1,*, Mark S. Udevitz1, Ron Kwok2, Anthony S. Fischbach1, David C. Douglas3

1US Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508, USA
2Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA
3US Geological Survey, Alaska Science Center, 3100 National Park Road, Juneau, Alaska 99801, USA

ABSTRACT: The Pacific walrus Odobenus rosmarus divergens is a large Arctic pinniped of the Chukchi and Bering Seas. Reductions of sea ice projected to occur in the Arctic by mid-century raise concerns for conservation of the Pacific walrus. To understand the significance of sea ice loss to the viability of walruses, it would be useful to better understand the spatial associations between the movements of sea ice and walruses. We investigated whether local-scale (~1 to 100 km) walrus movements correspond to movements of sea ice in the Bering Sea in early spring, using locations from radio-tracked walruses and measures of ice floe movements from processed synthetic aperture radar satellite imagery. We used generalized linear mixed-effects models to analyze the angle between walrus and ice floe movement vectors and the distance between the final geographic position of walruses and their associated ice floes (displacement), as functions of observation duration, proportion of time the walrus was in water, and geographic region. Analyses were based on 121 walrus–ice vector pairs and observations lasting 12 to 36 h. Angles and displacements increased with observation duration, proportion of time the walrus spent in the water, and varied among regions (regional mean angles ranged from 40° to 81° and mean displacements ranged from 15 to 35 km). Our results indicated a lack of correspondence between walruses and their initially associated ice floes, suggesting that local areas of walrus activities were independent of the movement of ice floes.

KEY WORDS: Pacific walrus · Odobenus rosmarus · Bering Sea · Sea ice · Telemetry · RADARSAT · RGPS · SAR

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Cite this article as: Jay CV, Udevitz MS, Kwok R, Fischbach AS, Douglas DC (2010) Divergent movements of walrus and sea ice in the northern Bering Sea. Mar Ecol Prog Ser 407:293-302.

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