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USGS Researchers Track Walrus Movement During Warm Season

As sea ice depletes off the coast of Alaska, Pacific walruses must adapt to the changing climate.

U.S Geological Survey researchers are currently attempting to track 35 walruses off the northwestern coast of Alaska to research how the marine mammals are adapting to the changing environment. Due to the depletion of sea ice, an element crucial to the life cycle of Pacific walruses, the animals have developed new foraging and movement habits for the late summer and fall seasons.

“With the loss of sea ice, it opens up the opportunity for other activities to occur in walrus habitat which can also impact the walruses, so it's a pretty complex system,” said Chad Jay of the USGS.

Researches are attaching satellite radio tags to the walrus as part of an ongoing study to monitor the animal’s response to environmental changes.

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Jay, a Research Ecologist specializing in walrus population ecology with the USGS Alaska Science Center, described some of the ways walruses depend on sea ice in their lifetime.

“One of them is give birth on the sea ice and nurse their young on the sea ice,” he said in a podcast from March of this year. “They use the sea ice to rest, so with the reduction of sea ice, it really is forcing walruses into behaviors that they have not used in the past.”

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However as the sea ice recedes past the continental shelf, a gradually sloping shallow sea area, walruses must respond by hauling out onto the beaches of Alaska and Russia.

James MacCraken, Walrus Program Supervisor with U.S Fish & Wildlife Service in Anchorage, Alaska, said though sea ice is at it’s minimum during the month of September, this had not been an issue in prior seasons.

“In the past, ice remained over the relatively shallow waters of the outer continental shelf of the Chukchi Sea where female walruses spend the summer,” MacCraken said. “This situation provided very good conditions for female walrus and their calves in terms of acquiring food, shelter from storms, and isolation from predators.”

According the USGS, which has been conducting research on Pacific walruses since 2004, the walruses are hauling out earlier and in higher numbers each year. While in 2010, walruses began hauling out in late August; they arrived almost a month earlier in 2011.

MacCraken said these changing environmental conditions are likely due to increased greenhouse gas emissions.

“The changes in sea ice amount and thickness in the Chukchi and Bering Sea, as well as the rest of the arctic over the last two decades, is attributable to a warming ocean and atmosphere which are most likely due to increased greenhouse gas concentrations in the atmosphere,” he said.

The depletion in sea ice has negative affects for three reasons, MacCraken said.

The haul outs of walruses are often very large, he said, often totaling between 10,000 to more than 20,000 animals.

“Adults are often jockeying for position and calves can get separated from their mothers and get trampled to death,” MacCraken said. “So there is a baseline level of mortality at large haulouts that probably does not occur or is not as great as when the animals are spread out in smaller groups on the ice.”

Secondly, when walruses feel threatened, for example by bears or people, they respond en masse, resulting in enormous stampedes.

“Hundreds of calves can be trampled in these stampedes,” MacCraken said.

Lastly, with such a concentrated population of walruses, prey in the surrounding area also depletes.

Walruses are also harvested in Alaska, Jay explained.

The high level of future harvests, Jay said, as well as the diminished sea ice in the Chukchi Sea could have the greatest impact on future walrus populations.

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