Atlantic Walrus Benefits from Global Warming

Climate Change Improves Walrus Feeding Grounds

Dec 24, 2008 John Blatchford

As Arctic glaciers retreat the Atlantic Walrus Population is Recovering.

Walruses almost became extinct in the Atlantic due to whaling. They are now doing well, and climate changes seem to suit them. Retreating coastal glaciers leave rich clam beds, which walruses adore.

Walrus Evolution and Living Populations

Walruses (Odobenus rosmarus) evolved from bear-like ancestors alongside the seals and sea-lions. They developed a peculiar ‘sucking’ way of feeding and specialised in capturing and eating molluscs such as clams. Only one living species remains (there were once more than twenty), with two or three distinct subspecies. The Atlantic Walrus (O. rosmarus rosmarus) is thought to be the ancestor of the Pacific Walrus (O. rosmarus divergens), and a third small population in the Laptev Sea (O. rosmarus laptevi) is clearly related – but might have descended from either of the others (no detailed DNA analysis has yet been carried out).

Walruses as a group probably diverged early from the seals/sea-lions, adopting their specialised feeding methods and exploiting benthic molluscs. The ancestors of the modern walrus moved north in the Atlantic towards the Arctic and adapted to cold water, later being pushed south with glaciation and allowing a few to move into the Pacific via the ‘Central American Seaway’ (a connection which once existed between the Atlantic and the Pacific).

Walrus Feeding Methods

Walruses are shallow divers who spend their time snuffling around on the seabed. They have a spectacular moustache of sensitive hairs (rather like cats’ whiskers), which allows them to find molluscs buried in the sediment. Once located the mollusc (usually a clam) is held in the muscular lips and the tongue is used (with the highly modified palate) to create a very powerful ‘suck’. The soft body of the clam simply slithers out of the shell and is swallowed.

Rummaging around on the bottom of shallow seas stirs up the sediment and nutrients, and it is thought that walrus feeding activity is important in maintaining the productivity of shallow Arctic waters. Walruses are seen as a ‘keystone’ species.

Walruses and Global Warming

Climate changes are causing many glaciers to retreat. Those glaciers which once extended out into the sea (and provided suitable feeding grounds for Belugas) are now moving back inland leaving newly exposed areas of seabed for clams. This is very good for walruses (less so for Belugas!) and helps explain their remarkable recovery in the North Atlantic from near extinction due to whaling. Current population estimates suggest about 200,000 Pacific Walruses, around 20,000 Atlantic, and maybe as many as 10,000 in the Laptev Sea.

The copyright of the article Atlantic Walrus Benefits from Global Warming in Marine Biology & Oceanography is owned by John Blatchford. Permission to republish Atlantic Walrus Benefits from Global Warming in print or online must be granted by the author in writing.

Walrus Face