EPOW - Ecology Picture of the Week

Walrus on Ice

Pacific Walrus (Odobenus rosmarus divergens), Family Odobenidae
Chukchi Sea, Alaska USA

Explanation:  This week we find ourselves flying in a small, single-engine fixed-wing aircraft, some 30 miles or so out onto the Arctic Ocean, doing aerial surveys of Pacific walruses, one of the two global subspecies (the other is in the north Atlantic).  

This is the Chukchi Sea, and Alaska is well beyond the oceanic horizon far to the south of us.  

After traversing many air miles over seemingly endless sea ice, we start spotting groups hauled out onto scattered ice floes.  It is instantly apparent that, for some reason, walruses love to huddle into tight groups even if there is plenty of room to disperse widely onto sea ice.  

Perhaps this is an anti-predator herding behavior such as found in ungulates such as antelope of the Serengeti of Africa.  But what would possibly have the audacity to attack such a large and temperamental foe?  Walruses have just two natural enemies:  orcas (killer whales) and polar bears.

Actually, make that three:  humans, too, hunt walruses, and have done so sustainably probably for millennia for subsistence needs ... until the 18th and 19th centuries when Europeans engaged in massive walrus hunts during their quests for seals and whales.  

What will be the fate of the walrus as the Arctic Sea ice
continues to melt more completely and earlier each summer,
under global climate change?

Analyses predict dire times ahead.

Information:  
     Jay, C. V., and A. S. Fischbach. 2008. Pacific walrus response to Arctic sea ice losses. US Geological Survey Fact Sheet 2008-3041 (May). USGS, Alaska Science Center, Anchorage, Alaska. 4 pp.
     Jay, C. V., B. G. Marcot, and D. C. Douglas. 2011. Projected status of the Pacific walrus (Odobenus rosmarus divergens) in the 21st century. Polar Biology 34(7):1065-1084.