Walrus areas of use in the Chukchi Sea during sparse sea ice cover
The Pacific walrus (Odobenus rosmarus divergens) feeds on benthic invertebrates on the continental shelf of the Chukchi and Bering seas and rests on sea ice between foraging trips. With climate warming, ice-free periods in the Chukchi Sea have increased and are projected to increase in frequency and...
| Main Authors: | , , |
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| Format: | Dataset |
| Language: | unknown |
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U.S. Geological Survey
2012
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| Online Access: | https://dx.doi.org/10.5066/f7c24tc3 https://www.sciencebase.gov/catalog/item/508ef7f0e4b0b59cf7f5a809 |
| Summary: | The Pacific walrus (Odobenus rosmarus divergens) feeds on benthic invertebrates on the continental shelf of the Chukchi and Bering seas and rests on sea ice between foraging trips. With climate warming, ice-free periods in the Chukchi Sea have increased and are projected to increase in frequency and duration. We radio-tracked walruses to estimate areas of walrus foraging and occupancy in the Chukchi Sea during June-November of 2008-2011, years when sea ice was sparse over the continental shelf. The earlier and more extensive sea ice retreat in June-September and delayed freeze-up of sea ice in October and November, allowed walruses to arrive earlier, occupy slightly more northern areas, and stay later in the Chukchi Sea than in the past. The lack of sea ice over the continental shelf in September-October caused walruses to forage in nearshore areas in contrast to offshore areas in the past. Walruses rarely moved into deep waters of the Arctic Basin when sea ice retreated off the shelf. Walruses foraged in most areas they occupied, and areas of concentrated foraging generally corresponded to regions of high benthic biomass, such as in the northeastern (Hanna Shoal) and southwestern Chukchi Sea. A notable exception was the occurrence of concentrated foraging in a nearshore area of northwestern Alaska that is apparently depauperate in walrus prey. With increasing sea ice loss, it is likely that walruses will increase their use of coastal haul-outs and nearshore foraging areas, with consequences to the population that are yet to be understood. Data is structured by month, which ranges from June (6) through November (11). Within each month we estimated walrus utilization distributions using two methods: ("Foraing") by weighting the kernel density distribution by the amount of time spent foraging during each recorded track segment. We present contour intervals ranging from 10th to 95th percentile. Portable Network Graphic files for each month are provided along with a Portable Network Graphic file for the legend. Areas outside of the 95th percentile contour are indicated as transparent. |
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