Divergent movements of walrus and sea ice in the northern Bering Sea
Return to Arctic Science for Decisions Home
Full Publication: https://doi.org/10.3354/meps08575Product Type: Journal Article
Year: 2010
Authors: Jay, C. V., M. S. Udevitz, R. Kwok, A. S. Fischbach, and D. C. Douglas
Suggested Citation:
Jay, C. V., M. S. Udevitz, R. Kwok, A. S. Fischbach, and D. C. Douglas. 2010. Divergent movements of walrus and sea ice in the northern Bering Sea. Marine Ecology Progress Series 407:293-302. doi:10.3354/meps08575
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 40o to 81o 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.
Keywords: Pacific Walrus, sea ice loss, movement
Annotation
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. 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. This lack of correspondence suggests that sea ice movements do not necessarily determine the extent of walrus foraging and may not prevent walruses from intensely feeding on local benthic prey. Availability of benthic prey could lead walruses to preferentially select certain areas for foraging, regardless of sea ice movements. Any activities such as shipping that interfere with walrus foraging activities in these important areas could have detrimental effects on the walrus population.