Enhydra lutris

Sea Otter

Family: Mustelidae · Class: Mammalia · Order: Carnivora

The sea otter is the smallest marine mammal in North America and the largest member of the weasel family. Adult males measure 1.2 to 1.5 meters (4 to 5 feet) in length and weigh 22 to 45 kilograms (49 to 100 pounds), while females are smaller at 1.0 to 1.4 meters (3.3 to 4.6 feet) and 14 to 33 kilograms (31 to 73 pounds). The dense fur consists of two layers: long guard hairs and a thick undercoat containing up to 165,000 hairs per square centimeter, providing insulation in cold marine waters. Coloration ranges from dark brown to blonde, with older individuals often displaying lighter colored heads and necks. Sea otters historically ranged from northern Japan to Baja California, Mexico. In California, the current population is restricted to coastal waters from approximately Half Moon Bay in San Mateo County south to Point Conception in Santa Barbara County. This represents a fraction of their historical California range, which extended from the Oregon border to Baja California. The species was extirpated from most of its range by intensive fur hunting in the 18th and 19th centuries. Sea otters inhabit nearshore marine environments, typically within one kilometer of shore in waters less than 40 meters (130 feet) deep. They require rocky reefs, kelp forests, and soft sediment areas that support their prey species. Kelp forests provide both foraging habitat and protection from storms and predators. The species rarely comes ashore, spending most of its life in the water. Sea otters are specialized predators of marine invertebrates, using tools to extract and process prey. Their diet consists primarily of sea urchins, abalone, crabs, clams, mussels, and other shellfish. They are one of the few marine mammals to use tools, employing rocks to break open hard-shelled prey while floating on their backs. Females give birth to a single pup after a gestation period of approximately four to five months, with delayed implantation extending the total reproductive cycle to nearly one year. Pups remain dependent on their mothers for five to six months. The California sea otter population is listed as threatened under the Endangered Species Act, designated in 1977. According to the U.S. Geological Survey's annual spring census, the California population numbered 3,272 individuals in 2024, representing a slight increase from previous years but still well below historical levels. The species faces ongoing threats including oil spills, fishing gear entanglement, disease, shark predation, and climate change impacts on prey availability. Recovery efforts include habitat protection, oil spill response planning, and research on population dynamics and threats. The species plays a crucial ecological role as a keystone predator, helping maintain kelp forest ecosystems by controlling sea urchin populations.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.