Walruses, classified as pinnipeds and marine mammals, spend a significant portion of their lives in the frigid Arctic waters. Despite their powerful aquatic abilities, the immediate answer to whether a walrus can breathe underwater is no. Like all mammals, the walrus relies on atmospheric air to survive and cannot extract dissolved oxygen from water using gills. Their remarkable time spent below the surface is due to unique biological adaptations that allow for prolonged breath-holding, but they must ultimately return to the air to replenish their oxygen supply.
The Immediate Answer Why Walruses Must Surface
The fundamental reason a walrus cannot breathe underwater lies in its anatomy, possessing lungs rather than the specialized gills of fish. This organ system requires the intake of oxygen from the air for gaseous exchange. The walrus, a massive animal weighing up to 4,000 pounds, needs a substantial volume of oxygen to fuel its bodily processes. This means that the carbon dioxide waste product built up during a dive must be expelled, demanding a return to the surface.
A walrus’s respiratory system is designed for high-efficiency breathing at the surface to maximize air intake before a dive. Even with adaptations, the metabolic demand of such a large body constrains the time it can remain submerged. Once stored oxygen is depleted and carbon dioxide levels become too high, the physiological drive to breathe forces the animal to surface. They typically spend about one minute at the surface after a dive to fully ventilate their lungs.
The Walrus’s Underwater Toolkit
The walrus is equipped with several physiological mechanisms that maximize its time underwater, traits shared by many deep-diving marine mammals. These adaptations begin with an enhanced capacity for oxygen storage, particularly in the muscles and blood. Muscle tissue contains a high concentration of the oxygen-binding protein myoglobin, which acts as an internal oxygen reserve. This specialized protein is much more efficient at storing oxygen than the hemoglobin found in the bloodstream.
When a walrus begins a dive, it triggers the mammalian dive reflex, which includes a dramatic reduction in heart rate known as bradycardia. This reflex conserves the limited oxygen supply by slowing blood circulation. Simultaneously, the walrus employs peripheral vasoconstriction, shunting blood away from non-essential organs and tissues that tolerate low oxygen levels. This action prioritizes the delivery of oxygenated blood to the brain and the heart, maintaining the function of these vital organs.
Life Below the Surface Diving Behavior and Purpose
Walruses spend a significant amount of time underwater, primarily to locate and consume food. Their foraging dives are typically short, lasting between five and eight minutes, with average depths ranging from 30 to 80 meters. However, they are capable of much longer submersions, with maximum documented breath-holds reaching up to 30 minutes and recorded depths exceeding 500 meters.
The main objective of their time beneath the ice and water is to search for benthic invertebrates, which are organisms living on or in the sea floor. These prey, such as clams and mollusks, are located using the walrus’s highly sensitive whiskers, called vibrissae. These stiff, tactile whiskers sense the movements and shapes of food buried in the muddy substrate. Once prey is found, the walrus uses powerful suction created by its tongue and mouth to extract the soft tissue from the shells.