Walruses are large marine mammals well-suited to the harsh conditions of their Arctic habitat. These impressive creatures, characterized by their immense size and prominent tusks, spend a significant portion of their lives in cold waters. Their ability to hold their breath for extended periods underwater is a remarkable adaptation that plays a central role in their survival and daily activities.
How Long Walruses Hold Their Breath
Walruses can hold their breath underwater for extended periods, with some individuals recorded remaining submerged for up to 30 minutes. However, their typical dives are considerably shorter, lasting between 5 to 10 minutes. Even when sleeping underwater, they can hold their breath for 4 to 5 minutes.
Biological Adaptations for Extended Dives
Walruses exhibit several physiological adaptations that enable their prolonged underwater dives. One such adaptation is bradycardia, where their heart rate significantly slows during submersion, reducing it by as much as 90%. This conserves oxygen by lowering the body’s metabolic rate. Alongside bradycardia, walruses utilize peripheral vasoconstriction, redirecting blood flow. This ensures oxygen-rich blood primarily supplies vital organs like the brain and heart, while flow to less critical areas such as muscles and skin is temporarily reduced.
Their muscles contain a high concentration of myoglobin, an oxygen-binding protein storing oxygen within muscle tissues. This oxygen becomes available as muscle oxygen levels decrease during a dive. They also possess a developed muscle acid-buffering capacity. This ability helps them manage lactic acid, a byproduct of anaerobic respiration accumulating when oxygen stores are depleted. Lactic acid is released into the bloodstream only after the walrus surfaces from a dive.
Life Underwater: Foraging and Behavior
A primary reason walruses undertake extended dives is to forage for food on the seabed. They are benthic feeders, predominantly searching for invertebrates on or within the ocean floor. Their diet largely consists of bivalve mollusks, particularly clams.
To locate their prey in often murky underwater environments, walruses rely on their highly sensitive whiskers (vibrissae). They move their snouts along the seafloor, rooting through sediment to detect hidden organisms. Once prey is located, walruses use a powerful suction method to extract soft bodies from their shells. They seal their lips around the prey and rapidly withdraw their piston-like tongue, creating a vacuum that pulls the animal out. Walruses swallow their food whole without chewing.
While walruses are capable of diving to depths exceeding 500 meters, these are exceptional. Most of their foraging dives are relatively shallow, occurring at depths of less than 80 meters, often between 10 and 50 meters. During a single feeding session, an adult walrus can consume between 3,000 and 6,000 clams.