Walruses are large, specialized pinnipeds adapted for life in the Arctic, spending significant time navigating frigid waters and resting on ice or land. Their survival depends on efficient swimming, which allows them to access essential feeding grounds and migrate across vast distances. These massive marine mammals move with surprising grace and power through the ocean, a stark contrast to their clumsy appearance on land.
How Walruses Navigate Water
Walruses propel their large bodies through the water using a unique swimming style. The primary source of thrust comes from the massive, paddle-like hind flippers, which alternate strokes to drive the animal forward. This alternating movement allows for sustained speed, typically averaging around 7 kilometers per hour (4.3 mph) during normal transit.
While the hind flippers provide the power, the fore-flippers serve as rudders, providing precise steering and maneuvering capabilities. Walruses often hold their fore-flippers close to their bodies while swimming, deploying them for stability or quick changes in direction. This locomotion is much more effective than their movement on solid surfaces, where the ability to rotate their hind flippers under the body allows for an awkward form of walking known as “hauling out.” For short periods, such as escaping a threat, a walrus can achieve bursts of speed up to 35 kilometers per hour (21.7 mph).
Physiological Limits of Diving
Walruses possess several biological mechanisms that conserve oxygen and manage the physical demands of diving. A primary adaptation is the diving reflex, which includes bradycardia, a dramatic slowing of the heart rate. This reflex decreases the overall metabolic rate and prioritizes oxygen delivery to the most sensitive organs, such as the brain and the heart, by shunting blood away from tissues that are more tolerant of low oxygen levels.
Their musculature contains a high concentration of the oxygen-binding protein myoglobin, which allows muscles to store a significant amount of oxygen directly. Walruses typically stay submerged for five to eight minutes, though they have the capacity to remain underwater for up to 10 minutes on a single breath. Individuals have been observed to hold their breath for 25 minutes. The animal’s thick layer of blubber, up to 10 centimeters (3.9 inches) thick, provides insulation against the frigid Arctic water and serves as an energy reserve.
The Role of Swimming in Walrus Life
The most important use of swimming is for benthic foraging, or feeding along the seafloor. Walruses primarily seek bottom-dwelling invertebrates like clams, often using their sensitive whiskers to locate prey buried in the sediment. They generally feed in the shallow waters of the continental shelf, usually diving no deeper than 80 meters (262 ft), where prey is most abundant.
A single feeding dive can be highly productive; a walrus is capable of consuming more than 50 clams in a dive lasting approximately seven minutes. Swimming is instrumental for seasonal migration between feeding grounds and haul-out sites, which are necessary for resting and social activities. The water acts as a sanctuary, offering rapid escape from terrestrial predators like polar bears or aquatic threats such as killer whales.