Southern sea otter
Sea otter mother and pup in the Great Tidepool at Monterey Bay Aquarium Sea otter raft

Animal Facts

  • Scientific Name

    Enhydra lutris nereis

  • Animal Type

    Marine mammals

  • Habitat

    Kelp Forest

  • Diet

    crabs, snails, urchins, clams, mussels and other invertebrates

  • Size

    to 4 feet (1.2 m) and up to 50 pounds (23 kg) for females and 70 pounds (32 kg) for males

  • Relatives

    weasels, skunks, river otters; Family: Mustelidea (sea otters are the only exclusively marine member of this family)

  • Habitat

    Kelp Forest

  • Range

    California: From San Mateo County in the north to near Santa Barbara in the south

    Sea otter range map

Natural History

A member of the weasel family, the sea otter is the smallest marine mammal in North America. The southern, or California, sea otter ranges along the coast from San Mateo County southward through Monterey County and down to Santa Barbara County.

Unlike other marine mammals, sea otters don't have a thick layer of blubber. To stay warm in chilly ocean waters, they wear the world's densest fur—at its thickest, this two-layer fur is made up of more than a million hairs per square inch. (You've probably got 100,000 hairs or less on your whole head!) In order to keep their luxurious coats waterproof, otters spend many hours a day cleaning and grooming. Such good grooming coats their fur with natural oils from their skin and fluffs it with insulating air bubbles.

In Monterey Bay

These charismatic critters are among the most easily observed marine mammals in the bay. They're often spotted floating and foraging among kelp forests along the outer coves and bays but can sometimes be seen off sandy beaches—and even local harbors. Sea otters are a frequent sight off the Aquarium's ocean-view decks and occasionally even pay a visit to our Great Tide Pool. They're also found in Elkhorn Slough.

Sea otters play an essential role in the health of Monterey Bay's kelp forest and estuary ecosystems. They eat sea urchins and other animals that graze on giant kelp, keeping them in check so the kelp forests can thrive and support a rich community of plants and animals. Similarly, sea otters keep estuary ecosystems healthy by eating crabs. This in turn allows sea slugs to thrive and eat algae that would otherwise coat and smother the eelgrass that fish need for food and shelter.

Visit our sea otter exhibit


Sea otters once thrived from Baja California and around the Pacific Rim to Russia and Japan before fur hunters nearly exterminated them in the 1700s and 1800s. The California population has grown from a group of about 50 survivors off Big Sur in 1938 to nearly 3,000 animals today. Although their numbers have increased, sea otters still face serious risks: oil from a single tanker spill near San Francisco or off the Central Coast would threaten the entire California sea otter population. The center of the population's range—from Monterey Bay to south of the Big Sur coast—can't support higher numbers of sea otters, so they need to keep expanding their range to find new areas with abundant food. Bites from white sharks is a major threat to sea otters in this area.

The Aquarium partners with state, federal and academic researchers to study otters in the wild. The more we learn about sea otter behavior, biology and health, the better we can protect these threatened animals.

Learn about our work to save sea otters

Cool Facts

  • An otter fuels its fast metabolism by eating up to a quarter of its weight in food a day. (A 150-pound person would have to eat 35 to 40 pounds of food a day to match that!)
  • A sea otter may hunt on the seafloor, but always returns to the surface to eat. Floating there on its back, it uses its chest as a table. (And if dinner's a crab or clam, the otter may use a rock to crack open its prey.)
  • An otter's coat has pockets—pouches of loose skin under each forearm. An otter uses them to stash prey during a dive, which leaves its paws free to hunt some more.
  • Unlike the sea otters found in Alaska, sea otters on California's central coast don't eat fish.

More Information

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