Sea otters are marine mammals fully adapted to aquatic life in nearshore coastal environments. These captivating creatures spend almost their entire existence in the ocean. They play an important role as a keystone species, particularly in controlling sea urchin populations. This helps maintain the health and balance of kelp forest ecosystems across the North Pacific coasts, contributing to their biodiversity.
Typical Dive Times
Sea otters typically spend relatively short periods underwater during their routine activities. Foraging dives, where they actively search for food, usually last between one and three minutes. While most dives are brief, sea otters can remain submerged for longer durations when necessary. Exceptional dive times have been recorded, with some individuals staying underwater for up to five to eight minutes. The length of a dive is influenced by factors such as the type of prey, water depth, and whether they are hunting or moving between locations.
Remarkable Diving Adaptations
Sea otters have specialized physiological adaptations that allow them to thrive in cold ocean waters and perform dives. Unlike many other marine mammals, they do not possess a blubber layer for insulation. Instead, they rely on an exceptionally dense coat of fur, the thickest of any animal, to trap a layer of air close to their skin for warmth. This trapped air also contributes to their natural buoyancy, which they manage when diving.
Sea otters have a large lung capacity, approximately 2.5 times greater than similar-sized land mammals, which aids in oxygen storage for underwater excursions. Their bodies are also efficient at distributing and storing oxygen. They have a higher concentration of oxygen-storing proteins, such as hemoglobin in their blood and myoglobin in their muscles, ensuring vital tissues receive adequate oxygen during dives. When submerged, sea otters exhibit bradycardia, where their heart rate slows down, and peripheral vasoconstriction, where they constrict blood vessels to non-essential organs. These mechanisms are part of the mammalian dive reflex, conserving oxygen for the brain and heart.
Why Sea Otters Dive
Sea otters primarily dive underwater to forage for food. They search for a variety of prey items on the seafloor, including shellfish like clams, mussels, and abalones, as well as crustaceans such as crabs, and sometimes slow-moving fish. Their highly sensitive whiskers are used to locate prey in dark or murky waters by touch. They then use their strong forepaws to pry it from rocks or dig it out of the sediment.
Sea otters use tools to access their meals. They often use rocks as anvils to crack open the hard shells of their prey. These tools are sometimes stored in a loose pouch of skin under their forelegs, allowing them to carry multiple items during a single foraging trip. The specific type of prey and foraging strategy directly influence the duration and depth of their dives. Beyond foraging, sea otters may also dive to evade predators or to travel between different resting spots.