August 19, 2011

Melting Arctic Sea Ice Forcing Walruses Onto Shores Of Alaska

The U.S. Geological Survey (USGS) said Thursday that it would attempt to attach 35 satellite radio-tags to walruses on the northwestern coast of Alaska as part of an ongoing study into how the mammals are responding to reduced Arctic sea ice conditions during late summer and fall.

The fast-melting Arctic sea ice seems to be pushing the walruses out onto land, with many moving near the area where oil leases have been sold, the agency said.

"Sea ice is an important component in the life cycle of walruses," said Chad Jay, research ecologist with the USGS Alaska Science Center.

"These tracking studies will help us to better understand how top consumers in the arctic ecosystem may be affected by changes in sea ice habitats."

The extent of Arctic sea ice has been less in recent summers, and walruses have been hauling out on beaches in Alaska and Russia over the past few years. Last September, the loss of sea ice caused approximately 10,000 to 20,000 walruses to move onto land.   Â

USGS researchers are now working with Alaskan villagers to attach radio transmitters on some of the hauled-out walruses to track their movements around the Chukchi Sea.

Walruses spend most of their lives at sea, frequently diving hundreds of feet to the bottom of the continental shelf to feed.  The marine mammals rely upon sea ice as platforms to give birth, nurse their young, evade predators and to rest between feeding bouts.  However, when the sea ice recedes past the continental shelf into very deep waters of the Arctic Basin, the walruses move onto land.  Â

The USGS hopes that radio-tracking the walruses' movements in water and to and from land will provide critical insight into their movements and feeding behaviors in response to changing Arctic sea ice conditions.

"The ice is very widely dispersed and there is little of it left over the continental shelf," said Jay in a statement on Wednesday.

"Based on our tracking data, the walruses appear to be spreading out and spending quite a bit of time looking for sea ice."

Compared to last year's enormous haul-out, there are few walruses on land, and there is no firm count, Jay said.

"There is a lot less ice than there used to be on the continental shelf this time of year," he said.

"So we might be headed into a new normal."

Transmissions from the radio-tagged walruses provide researchers with valuable information about where these marine mammals are in the Chukchi Sea.  The USGS tracks and displays these positions in a weekly-updated graph, which can be viewed at http://alaska.usgs.gov/science/biology/walrus/2011animation_Norseman.html).

The graphic shows where the walruses were when they were first tagged (denoted as red Xs) and how they moved around the water (denoted as yellow dots).  The graphic also shows alterations in sea ice cover in the far north, indicating virtually ice-free conditions in areas where the walruses are moving.

Many are now within the boundaries of an oil lease sale area on the northwestern Alaska coast that extends far into the Chukchi Sea.

Royal Dutch Shell, ConocoPhillips and Statoil hold leases in the Chukchi Sea, although no drilling has started.

Last month, Arctic sea ice dropped to its lowest extent for any July since satellite records began being kept in 1979, according to the U.S. National Snow and Ice Data Center.   The sea ice typically reaches its lowest extent for the year in September.

Walruses are protected under the Marine Mammal Protection Act, which means they cannot be harvested, imported, exported or used in interstate commerce.  In February, the U.S. Fish and Wildlife Service listed Pacific walruses as candidates for protection, though not protection itself.

Photos and additional information about the USGS Pacific walrus studies can be viewed at http://www.usgs.gov/blogs/features/.


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