The walrus, Odobenus rosmarus, is a massive marine mammal living in the frigid, ice-covered waters of the Arctic. Its body, which can weigh over a ton, is built to thrive in two environments: the open ocean and the solid surfaces of sea ice or coastal land. This dual existence demands a specialized movement system that enables both graceful aquatic propulsion and a capable terrestrial gait.
Aquatic Movement: The Mechanics of Swimming
In the water, the walrus adopts a sleek, streamlined posture, relying heavily on its hind flippers for primary propulsion. This swimming technique, known as pelvic oscillation, involves powerful, alternating strokes of the rear flippers, similar to the movement of true seals. The large fore-flippers, or pectoral fins, are primarily tucked against the body during fast swimming, used mainly for steering, braking, and maneuvering at slow speeds. This method of thrust generation is distinct from that of sea lions, which use their front flippers like oars to “fly” through the water.
A thick layer of blubber provides insulation against the Arctic cold and contributes to buoyancy, helping the walrus conserve energy. The walrus possesses an inflatable air sac located in the throat region, which serves as a flotation device. This unique feature allows the animal to float effortlessly and even sleep while bobbing vertically in the water.
Terrestrial Movement: Walking on Flippers
The walrus possesses a distinct anatomical adaptation that makes its movement on land or ice more capable than that of true seals. The walrus can rotate its triangular hind flippers forward and underneath its pelvis, allowing its entire body to be lifted off the ground. This rotation enables a stable, four-limbed, quadrupedal gait, similar to sea lions and fur seals. True seals lack this ability and must instead move by laboriously “galumphing,” or undulating their bodies in a caterpillar-like motion.
On solid surfaces, the walrus uses its fore-flippers, positioned at right angles to the body, for support, balance, and pushing off. While not built for speed on land, this quadrupedal walk allows for deliberate movement across ice floes or rocky beaches. The skin on the soles of its flippers is rough and thick, providing the necessary traction to navigate slippery ice and snow.
Locomotion Metrics: Speed and Endurance
Walruses are built for endurance and burst speed in their marine environment, not for rapid terrestrial travel. When swimming at a sustained, average pace, they cruise around 4.3 miles per hour. When pursuing prey or escaping a threat, they are capable of impressive burst speeds reaching up to 22 miles per hour.
On land, the walrus is significantly slower, but it can achieve a surprising run when necessary, with its maximum speed roughly matching that of a running human. Their endurance is displayed through their diving capabilities, which are crucial for bottom-foraging. Walruses commonly dive to depths of 30 to 40 meters to search for clams and other benthic mollusks, often staying submerged for up to 30 minutes at a time. While they can make deeper dives exceeding 500 meters, most foraging occurs in the shallow waters above the continental shelf.