The walrus (Odobenus rosmarus) is a massive marine mammal and an icon of the Arctic environment. These powerful pinnipeds spend a significant portion of their lives navigating icy waters and foraging on the sea floor. Their immense size and ability to thrive are linked to their impressive capacity for holding their breath underwater. The time a walrus can remain submerged varies widely between a routine foraging trip and its maximum physiological limit.
Maximum Duration and Typical Dive Times
A walrus’s typical underwater duration is far shorter than its maximum recorded time. A routine foraging dive usually lasts between five and twelve minutes. These shorter dives are sufficient because walruses prefer to hunt in relatively shallow waters, often between 20 and 80 meters deep. The absolute maximum breath-hold time recorded is considerably longer, documenting dives lasting up to 25 minutes. Deep-diving events have been documented, including one Atlantic walrus that reached a depth exceeding 500 meters, though that specific dive lasted only about thirteen minutes.
Specialized Physiology for Extended Dives
The ability of the walrus to sustain these long periods without air relies on a sophisticated suite of biological mechanisms common to marine mammals. When a walrus submerges, it triggers the mammalian dive reflex, an automatic response that conserves oxygen for the most vulnerable organs. This reflex includes a dramatic reduction in heart rate, a phenomenon known as bradycardia.
Simultaneously, the body initiates peripheral vasoconstriction, shunting blood away from tissues that tolerate low oxygen levels, such as the extremities and digestive system. This action prioritizes the limited oxygen supply for the heart and the brain. The walrus also possesses a higher concentration of the oxygen-binding protein myoglobin within its muscles compared to land mammals, providing a localized oxygen reserve.
This high myoglobin concentration, combined with a large overall blood volume, significantly increases the total oxygen storage capacity of the animal’s body. Furthermore, like other pinnipeds, the walrus has adaptations in its respiratory system, such as a flexible trachea, which allow its lungs to collapse under pressure. This collapse prevents the transfer of nitrogen gas into the bloodstream at depth, mitigating the risk of decompression sickness.
Utilizing Breath-Hold for Arctic Foraging
The primary motivation for a walrus’s breath-hold is to locate and consume its preferred food source on the seafloor. These animals are benthic feeders, hunting for invertebrates living in the sediment, such as bivalve mollusks and clams. A walrus uses its highly specialized sensory apparatus to navigate the dark, often murky, Arctic waters during these dives.
The walrus’s snout is covered in hundreds of stiff, highly sensitive whiskers called vibrissae. These vibrissae are rich with blood and nerve endings, allowing the animal to effectively “feel” for prey buried beneath the substrate, compensating for limited visibility. Once prey is located, the walrus employs a unique feeding technique.
The animal uses its vaulted palate and muscular tongue to create a powerful vacuum, sucking the soft body of the mollusk right out of its shell. Some walruses also use jets of water or active flipper movements to stir up the sediment and expose concealed prey. This efficient foraging method is supported by physiological dive adaptations, allowing the walrus to remain on productive feeding grounds to consume the large quantities of food required by its massive body.