The true sea otter, Enhydra lutris, is definitively confined to the North Pacific basin. This marine mammal is highly specialized for life in the ocean and rarely comes ashore. Any otter sightings along the Atlantic coast are instead the North American River Otter, a different species that frequently ventures into saltwater environments.
Where Sea Otters Actually Live
The sea otter’s geographic range is restricted to the shallow, nearshore waters of the North Pacific Ocean. This area extends from the northern islands of Japan, through the Russian coast and the Aleutian Islands, along the Alaskan coast, and south to the central coast of California. Historically, they occupied a continuous arc along the Pacific Rim before hunting reduced their numbers.
Sea otters prefer temperate coastal habitats, particularly those with dense kelp forests. These underwater forests provide a sheltered place to rest and anchor themselves while floating on the water’s surface. They rarely venture into waters deeper than 40 meters, spending nearly all their time within a half-mile of the shoreline. They forage, rest, and give birth entirely within the Pacific marine environment.
The Atlantic Otter Species
The animal frequently mistaken for a sea otter in Atlantic coastal regions is the North American River Otter, Lontra canadensis. This species is widespread across the eastern United States and Canada, including states bordering the Atlantic Ocean. The river otter is highly adaptable, thriving in a variety of aquatic habitats such as rivers, lakes, and freshwater marshes.
Despite their name, river otters are semi-aquatic and often utilize coastal areas. They venture into brackish estuaries and the saltwater of the Atlantic shoreline. Unlike sea otters, river otters spend significant time on land, where they create dens in abandoned burrows along riverbanks.
How to Tell the Two Otters Apart
Distinguishing between the two otter species requires observing differences in size, body shape, and behavior. Sea otters are substantially larger and heavier; adult males often weigh up to 90 pounds. In contrast, the male North American River Otter typically reaches a maximum weight of only about 30 pounds.
Physical Differences
The tails also offer a clear distinction. The sea otter has a short, thick, and flattened, paddle-like tail, while the river otter possesses a longer, streamlined, and tapered tail.
Behavioral Differences
Sea otters float on their backs when resting or eating, using their chest as a platform to consume hard-shelled invertebrates like sea urchins and clams. River otters, which primarily eat fish and amphibians, are more streamlined, often swimming on their stomachs, and rest primarily on land.