What Do Sea Otters Eat?

Sea otters depend almost entirely on shellfish as their main food source year-round. They hunt Pacific geoducks, California butterclams, and Pacific razor clams by diving to the seafloor and pulling them from sand and mud. Abalones and sea urchins are important prey that sea otters pluck from rocks and reef areas. Nuttall's cockles and black leather chitons provide nutrition throughout the year in coastal zones. Sea otters also eat cephalopods including the opalescent inshore squid and octopuses like the giant Pacific octopus when available. They hunt crabs, sea stars, and other invertebrates when their favorite shellfish are harder to find or depleted. Visit /wildlife to learn about other marine animals that depend on the ocean floor ecosystem. Sea otters have the highest metabolism of any marine mammal, requiring them to eat constantly to maintain body temperature and energy levels. You can learn more at /wildlife/california/sea-otter for California-specific information.

The types of shellfish and invertebrates sea otters eat changes significantly with seasons and ocean conditions. During spring and summer, when many species spawn and become more active and visible, certain prey becomes easier and more rewarding to catch. Fall and winter bring different species to peaks in activity, shifting what sea otters hunt most intensively. Some shellfish are bigger or more abundant during certain months creating seasonal preferences. Upwelling events bring nutrients that boost small organisms and invertebrates sea otters chase for food. Reproductive cycles in shellfish populations mean that at certain times of year, otters target younger, smaller individuals selectively. Storm waves and heavy rains can stir up sediment and make hunting more difficult or impossible. Seasonal changes in water temperature and ocean chemistry affect which species thrive in any given area at any given time of year.

Sea otters in California waters eat different species than otters in Alaska or Washington due to regional marine biodiversity. California coastal areas have abundant abalones and sea urchins that form a major part of the diet there. Check /wildlife/california/sea-otter for details about what sea otters hunt in California specifically. Alaska and Washington sea otters focus more heavily on clams and mussels because those shellfish are plentiful in their colder waters. Pacific geoducks are particularly common prey in northern areas where they thrive. Regional ocean temperature and currents control which shellfish thrive and reproduce successfully. Kelp forest areas support different invertebrate communities than rocky reefs or sandy bottoms. Sea otters that live near river mouths where freshwater mixes with saltwater encounter different prey than those in full ocean waters. Geography shapes the available menu for each sea otter population and influences diving behavior and range.

Sea otters are famous for using stones and rocks as tools to open difficult shellfish. They dive to the seafloor and collect shellfish, then float on their backs at the surface to rest and eat. While floating, they place a rock on their chest and pound shellfish against it repeatedly until the shell cracks open. This technique allows them to access food that animals without tools cannot eat successfully. Sea otters dive to depths of 40 meters or more to reach prey on the ocean floor. They use their sensitive paws to feel for prey hidden in crevices and sand. Young otters learn tool use by watching and copying their mothers' techniques. Adult sea otters carry favorite rocks in a pouch of skin that holds tools between diving sessions. This hunting method requires skill and patience but gives sea otters access to food other animals cannot obtain.

Mother sea otters nurse their pups for about six months, providing all nutrition through rich milk. At a few weeks old, pups start eating soft prey like sea urchin eggs and small invertebrates. Mothers catch shellfish and bring them to pups while still in the water, teaching them what is edible and safe. Young otters practice hunting by playing with prey and learning diving skills gradually. Pups follow mothers closely as they hunt, observing techniques used to find and capture food. Learning to use stones as tools takes several months and requires patience and repeated practice. By one year old, most young sea otters can hunt and eat independently. The transition from milk to solid food happens gradually over the first year of life. Mother sea otters remain protective during this critical learning period of their pups' development. Check /wildlife/alaska/sea-otter for information about young sea otters in Alaska.

Sea otters prefer to live in kelp forest areas and rocky reefs where shellfish are abundant year-round. They stay close to shore in shallow water rather than moving to deep ocean areas. Otters haul out on rocks and beaches to rest and groom between hunting sessions. Some sea otters have learned to visit areas near human settlements and fishing piers looking for easy meals. They sometimes eat fish caught in nets or bycatch from commercial operations. Kelp forests provide shelter and attract many invertebrates that sea otters hunt regularly. Pollution and coastal development can reduce the quality of sea otter habitat significantly. Human trash and debris sometimes injure otters or tangle their fur causing problems. Sea otters face challenges from oil spills and habitat loss due to human activities. Learn more at /wildlife/washington/sea-otter for information about sea otters in northern Pacific waters.

Sea otters are unique among marine mammals in relying entirely on invertebrates rather than fish. Seals and sea lions hunt mostly fish and squid rather than shellfish and invertebrates. Sea stars hunt similar prey to sea otters and eat many of the same species of mollusks. Walruses also dive to the seafloor to collect clams and mussels but are much larger and more powerful animals. Diving birds like cormorants hunt fish instead of shellfish and bottom-dwelling prey. Humans catch the same shellfish species that sea otters eat commercially in many regions. Sea otters actually help shellfish populations by controlling sea urchins that would overgraze kelp and plants. Their diet is completely different from fish-eating marine mammals in the region. Sea otters fill a unique ecological role in coastal food webs by eating invertebrates and preventing some species from becoming too numerous in any area.