Walruses have been massing in their tens of thousands on a small barrier island on the Alaskan coast of the Chukchi sea. With the arctic summer ice melt at its fourth largest on record, the phenomenon is thought to be due to the loss of ice in the area.
While walruses often haul-out (when pinnipeds temporary leave the water between periods of foraging) on the opposite Russian coast, seeing female walruses and their young on Alaskan beaches has been a rarer occurrence. In the last decade, marine scientists have been watching a pattern emerge: ‘Large female walrus haul-outs on the Alaskan coast had been “unusual” until 2007,’ says Lara Horstmann-Dehn, an Associate Professor of Marine Biology at the University of Alaska Fairbanks. ‘Since then, we have seen this in seven out of the past nine years. This current walrus haul-out near Point Lay seems to be similar in timing to previous years.’
Pacific walruses swim northwards in the summer, following floes of ice that free up as the season warms. Unable to swim indefinitely, they use their tusks to haul-out onto land and ice between foraging. From these floes, they can launch themselves into the shallow feeding grounds around the coast to dive for molluscs. In the past decade, however, the summer ice has retreated far over the Arctic basin. So far in the north, the sea floor is over two miles deep – too far for a feeding adult to dive.
While the new Alaska haul-outs coincide with diminishing ice and could be seen as a direct indication of global warming, correlation does not always equal causation. Thus, marine scientists are approaching the idea with caution. ‘This is a difficult question to answer, and currently the topic of many studies,’ says Horstmann-Dehn. ‘Walruses are ice-loving pinnipeds, however, with the ice being far over the Arctic basin – an area too deep for walruses to dive to the sea floor to feed – they need to find other areas to rest. It is not unprecedented behaviour, they are adapted to take advantage of terrestrial areas.
‘The question really is, how will this change from sea ice substrate to terrestrial haul-out affect the energy budget of walruses. They have to make longer foraging trips to get to their prey rather than jump off ice platforms. Also, [on land] human disturbance is a very real threat.’
While their conditions have been described as ‘overcrowded’, Horstmann-Dehn explains that ‘it is typical walrus behaviour to huddle in large, dense social groups with animals touching each other’.
Nonetheless, the arrival of the walruses has caused a brace of media to arrive in the area, posing a significant threat to the closely-packed animals. In the past, disturbing large herds has caused stampedes, resulting in the death of young offspring caught in the middle.
To deter interested parties and to urge the media to keep their distance, the community at Point Lay issued a statement in conjunction with the US Fish and Wildlife Service, the US Geological Survey and the National Oceanic and Atmospheric Administration: ‘The community does not have the capacity to house anybody visiting. This is a small community. Our population is only about 246 and it’s a subsistence community.’