Walruses are large marine mammals adapted to the Arctic. These powerful pinnipeds are recognizable by their prominent tusks, which are elongated canine teeth present in both males and females. They spend much of their lives in frigid waters and on ice floes or land haul-out sites across the Northern Hemisphere. Their substantial bulk, with adult males weighing over 2,000 kilograms, helps them thrive in this environment.
The Depths Walruses Reach
Walruses are capable of significant underwater excursions, with some recorded dives exceeding 500 meters (1,600 feet) in areas like Smith Sound between Greenland and Arctic Canada. Despite their capacity for such depths, walruses do not typically dive that far for daily activities. Their usual foraging grounds are found in much shallower waters, often between 10 to 100 meters (33 to 328 feet). While they can dive to approximately 70 to 90 meters (230 to 295 feet), they frequently undertake briefer dives.
Foraging Habits Beneath the Waves
Walruses primarily dive to forage for food, with their diet consisting largely of benthic invertebrates, meaning organisms living on or within the seabed. Bivalve mollusks, such as clams and mussels, constitute a significant portion of their diet, making up around 97 percent of what they consume. To locate buried prey in murky waters, walruses rely on their sensitive vibrissae, or whiskers. They root along the seafloor with their snouts, using their vibrissae to detect subtle movements of prey.
Once prey is detected, walruses employ a suction feeding method. They create a powerful vacuum by rapidly withdrawing their piston-like tongue into their mouth, sealing their lips around the bivalve to extract the soft body parts. This process often leaves the intact shells behind on the seabed. Walruses may also use jets of water from their mouths or wave their foreflippers to stir up sediment and expose buried organisms. An adult walrus can consume between 3,000 and 6,000 clams in a single feeding session.
Remarkable Diving Adaptations
Walruses possess several physiological mechanisms for underwater activities. They can slow their heart rate during a dive, a response known as bradycardia. This helps conserve oxygen by reducing the metabolic rate and directing oxygen supply primarily to essential organs like the brain and heart. They also have high concentrations of myoglobin in their muscles, a protein that efficiently stores and transports oxygen.
A thick layer of blubber, which can be up to 15 centimeters (6 inches) thick, provides insulation against the cold Arctic waters and serves as an energy reserve. This blubber also aids in buoyancy. When submerged, blood vessels near the skin constrict, shunting blood away from the surface and towards the core organs to conserve heat. Specialized pharyngeal muscles in their throat close to prevent water from entering their lungs during dives, allowing them to open their mouths without inhaling water.
Typical Dive Behavior
Walruses typically intersperse dives with periods at the surface. After approximately five to eight minutes of underwater activity, they typically spend about one minute breathing at the surface. While they can remain submerged for as long as 10 to 30 minutes, their average feeding dives are generally shorter. Foraging dives usually last between 5 to 20 minutes.
Their diving behavior is often determined by the distribution of their preferred prey. While occasional deep dives occur, most dives target shallower depths where bivalves and other bottom-dwelling invertebrates are abundant.