Sea Otter

The sea otter (Enhydra lutris) is the heaviest member of the weasel family and the only marine mammal that spends the majority of its life at the ocean surface, rarely coming ashore. Native to the coastal waters of the North Pacific, it inhabits kelp forests and nearshore rocky reefs from the Kuril Islands and Kamchatka Peninsula through the Aleutian archipelago and along the Pacific coast of North America as far south as central California. Unlike other marine mammals, it has no blubber and depends entirely on its exceptionally dense fur, the thickest of any mammal on Earth, to retain body heat in cold water.

Sea otters are a textbook keystone species: by preying on sea urchins, they prevent overgrazing of kelp forests, which in turn shelter hundreds of other species and sequester significant amounts of carbon. The global population was reduced to near extinction by the commercial fur trade in the 18th and 19th centuries, and while protections under the U.S. Marine Mammal Protection Act and international agreements have allowed partial recovery, the species remains listed as Endangered on the IUCN Red List. The main threats today include oil spills, entanglement in fishing gear, shark predation along the California coast, and the vulnerability of small, geographically isolated populations to disease and environmental disruption.