The walrus (Odobenus rosmarus) is a massive marine mammal instantly recognizable by its prominent tusks and dense facial whiskers, inhabiting the frigid, shallow waters of the Arctic and subarctic. This animal’s considerable bulk is supported by a highly specialized diet and unique feeding methods adapted to its icy environment. The walrus relies on the productivity of the ocean floor, where it spends much of its time foraging. Its feeding behavior involves locating and consuming the small, soft-bodied organisms that form the foundation of its caloric intake.
The Walrus’s Staple Diet
Walruses are classified as benthic feeders, meaning they primarily consume organisms that live on or in the seafloor. Their diet is overwhelmingly composed of marine invertebrates, with bivalve mollusks, particularly clams, serving as the preferred food source. They also consume other soft-bodied creatures, including sea cucumbers, snails (gastropods), various worms, and some crustaceans. This invertebrate-rich diet provides the fats and proteins necessary to maintain a thick layer of insulating blubber.
The specific composition of the diet shifts based on geographic location and season, reflecting the local availability of prey. While clams are the staple, walruses have been documented consuming organisms from over 12 different phyla, demonstrating flexibility in their foraging habits. They must acquire large quantities of these small, stationary animals to meet their immense physiological demands.
Specialized Foraging Techniques
To locate buried prey, walruses utilize their highly sensitive vibrissae, or whiskers, which form a dense mat around their snout. These stiff bristles are richly supplied with nerves and blood vessels, allowing the walrus to tactually scan the muddy or sandy bottom in low-visibility conditions. The sensitivity of these whiskers enables them to detect and differentiate tiny objects. As a walrus moves its snout along the sediment, the vibrissae sense the subtle presence of buried clams and worms.
Once prey is located, the walrus employs a powerful suction feeding mechanism to extract the soft tissues from the shell or sediment. The animal creates a vacuum by rapidly retracting its piston-like tongue and using strong mouth muscles, effectively vacuuming the invertebrate out of its burrow or shell. The soft parts of the prey are generally swallowed whole, as walruses do not typically chew their food, though they occasionally crush clam shells. Walruses have also been observed using jets of water propelled from their mouths to excavate prey buried up to 30 centimeters deep.
The walrus’s iconic tusks, which are elongated upper canine teeth, play a minor role in the primary feeding process. Analysis of abrasion patterns indicates they are primarily dragged through the sediment rather than used for deep excavation. Their main functions include helping the animal haul its massive body out onto ice floes, serving as anchors in strong currents while feeding, and acting in defense or dominance displays.
Energy Requirements and Dietary Exceptions
The sheer size of the walrus necessitates a massive daily caloric intake to maintain its body temperature and bulk. Adult walruses consume between 3% and 8% of their total body weight each day, requiring them to spend significant time foraging underwater. In a single feeding session, a walrus may consume anywhere from 3,000 to 6,000 clams, illustrating the volume of prey needed to satisfy their energy demands. These intensive feeding bouts allow them to fill their stomachs twice daily, often foraging in relatively shallow waters between 10 and 50 meters deep.
While the vast majority of the diet consists of invertebrates, some large male walruses, particularly in the Pacific subspecies, occasionally prey on other marine mammals, such as seals. This predatory behavior is an exception to the species’ typical diet. It is thought to be more common when benthic food resources may be less accessible. When consuming seals, the walrus uses powerful suction to remove the skin and blubber, which are the most energy-rich parts, leaving much of the carcass intact.