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Arctic climate: USGS scientists document walrus response to shrinking summer sea ice cover

A Walrus in the Chukchi Sea during a tagging survey onboard the Norseman II in June 2010. Photo courtesy Sarah Sonsthagen , U.S. Geological Survey.

New study a first step in understanding long-term impacts to walrus populations

By Summit Voice

SUMMIT COUNTY — Scientists with the U.S. Geological Survey say walruses in the Arctic are responding to shrinking summer sea ice by arriving earlier at their northern feeding grounds on the broad continental shelf of the Chukchi Sea.

When the sea ice over the continental shelf melts completely in the fall, they “hauled out” onshore in large aggregations and foraged for food closer to shore. Hauling out refers to the behavior associated with seals and walruses of temporarily leaving the water for sites on land or ice, according to the study published in the journal Marine Ecology.

The researchers said they’re not exactly sure how this may affect walrus populations in the long run, however it is known that immature walruses are more susceptible to mortality from trampling onshore, Additionally, hauling out onshore and using nearshore feeding areas may require more energy.

“The loss of sea ice is the ‘why’ for the change in walrus behavior; the tracking data tells us the ‘where’ in terms of their new forage patterns,” said USGS Director Marcia McNutt. “What awaits to be seen is ‘how much will it matter?'”

The longer open water season in the Arctic is creating opportunities for shipping, tourism, energy production and other human activities in this remote region. Data from this study will provide resource managers with basic information on areas important for walruses, such as the Hanna Shoal region, as human activities in the Arctic increase. The areas of walrus foraging overlap with oil and gas lease blocks administered by BOEM.

The information gained through tracking large marine mammals such as polar bears and walruses, is helping USGS scientists understand how disappearing Arctic sea ice is affecting the region’s ecosystems. The Arctic sea ice is melting faster than forecasted by many of the top climate models: the first ice free summer is now predicted to occur by 2035, perhaps as soon as 2025.

Using a simple darting system, scientists attached radio-tracking tags to 251 walruses in the Chukchi Sea. The tags transmitted the animals’ whereabouts and whether they were in the water and feeding. Using the tagging data gathered from 2008-2011, scientists created detailed maps of the walruses’ seasonal movements and feeding patterns relative to the location and amount of sea ice.

A new film, “Tracking Pacific Walrus: Expedition to the Shrinking Chukchi Sea Ice,” explores the walruses habitat and follows USGS researchers as they conduct their studies in the Arctic. The USGS-produced film contains exclusive footage of the large mammals in their natural habitat.

The study, published as this month’s feature article in the journal Marine Ecology Progress Series, is part of the USGS Changing Arctic Ecosystems initiative at the Alaska Science Center.

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