10 Facts About Sea Otters

Young sea otters can't sink and other fun facts

Sea otters are icons of marine conservation on the West Coast of the U.S. With their furry bodies, whiskered faces, and propensity to lay on their backs on the water, they are an easily-recognized and beloved marine mammal. 

Sea Otters Are Related to Weasels

The sea otter belongs to the weasel family.
Rolf Hicker/All Canada Photos/Getty Images

Sea otters are carnivores in the family Mustelidae — a group of animals that also includes weasels, badgers, skunks, fishers, minks, and river otters. What do these animals have in common? They share features such as thick fur and short ears. This thick fur keeps the animals warm ​but unfortunately has led to the over-hunting of many of these mustelid species by humans. 

There Is Only One Species of Sea Otter

Sea Otter in Monterey Bay,CA

Chase Dekker/ Wild-Life Images / Getty Images

Although there is just one species of sea otter — Enhyrda lutris, there are three subspecies. These are Russian northern sea otter (Enhyrda lutris lutris), which lives in the Kuril Islands, Kamchatka Peninsula, and Commander Islands off Russia; the northern sea otter (Enhyrda lutris kenyoni), which lives from the Aleutian Islands off Alaska, down to Washington state; and the southern sea otter (Enhyrda lutris nereis), which lives in southern California.

Sea Otters Live in the Ocean, But Can Also Live on Land

Sea otter (Enhydra lutris), Oregon, USA

Mark Conlin /Getty Images

Unlike some marine mammals like whales, who would die if they were on land for too long, sea otters can go up onto land to rest, groom or nurse. They spend most of their lives in the water, however, and can live their entire lives in the water if they need to. Sea otters even give birth in the water.

They Need to Keep Clean

Southern sea otter grooming its feet
Don Grall / Getty Images

Sea otters spend hours each day grooming their fur. It is important to keep their fur clean because it is their sole means of insulation. Unlike other marine mammals, sea otters don't have blubber. A sea otter's fur is made up of an undercoat and longer guard hairs. The air around the fur is heated by the sea otter's body heat, and this air keeps the sea otter warm.

Sea otters are heavily affected by oil spills due to their dependence on their fur for warmth. If oil covers a sea otter's fur, air cannot penetrate it and the sea otter will get too cold.  The infamous Exxon Valdez spill killed at least several hundred sea otters and affected the sea otter population in Prince William Sound for well over a decade, according to the Exxon Valdez  Oil Spill Trustee Council. 

Sea Otters Use Tools

Sea otter eating a crab
Jeff Foott / Getty Images

Sea otters eat fish and marine invertebrates like crabs, urchins, sea stars, and abalone. Some of these animals have hard shells, making it difficult to get the meat inside. This isn't an issue for the sea otter, which uses rocks as tools to crack the shells of its prey.

Built-In Storage

Sea otter lifting forelimbs
Cameron Rutt / Getty Images

Sea otters have a baggy patch of skin under their forelimbs, and this is used for storage. They can keep extra food in this spot, and also store a favorite rock for cracking the shell of their prey.

Young Sea Otters Can't Dive Underwater

Female Sea Otter Holding Newborn Pup Out Of Water, Prince William Sound, Southcentral Alaska,

Milo Burcham / Design Pics / Getty Images

Young sea otters have very wooly fur. This fur makes an otter pup so buoyant that it can't dive underwater. Before a mother otter leaves to forage, it wraps the pup young in a piece of kelp to keep it anchored in one spot. It takes 8-10 weeks for the pup to shed its initial fur. 

Social Animals Who Live in Rafts

Sea otters in kelp, Monterey Bay, California, USA
Mint Images - Frans Lanting / Getty Images

Sea otters are social, and hang out together in groups called rafts. Sea otter rafts are made up of either male otters​ or females and their young and can consist of anywhere from two to over 1,000 otters. 

Sea Otters Are Important Predators

Sea Otter (Enhydra lutris) eating sea urchin, Monterey Bay, California, USA
David Courtenay / Getty Images

Sea otters play an important role in the food web of the kelp forest, so much so that even terrestrial species are influenced by sea otter activity. When sea otter populations are healthy, urchin populations are kept in check, and kelp is abundant. Kelp provides shelter for sea otters and their pups and a variety of other marine organisms. If there is a decline in sea otters due to natural predation or other factors, such as an oil spill, urchin populations explode. As a result, kelp abundance decreases and other marine species have less habitat.

A study published in 2008 showed that when sea otter populations were abundant, bald eagles preyed primarily on fish and sea otter pups, but when sea otter populations declined due to predation by an increased population of orcas, bald eagles preyed more on marine birds.

A 2012 study showed the role sea otters can play in reducing carbon dioxide in the atmosphere. It found that if sea otter populations increase, urchin populations will be controlled and kelp forests will thrive. Kelp can absorb carbon dioxide from the atmosphere, and, the study found, that kelp can absorb as much as 12 times the amount of CO2 from the atmosphere than if it were subject to sea urchin predation. 

Hunted for Their Fur

Sea Otter Skins, Unalaska,1892

Gulf of Maine Cod Project, NOAA National Marine Sanctuaries; Courtesy of National Archives

The sea otter's thick, luxurious fur was sought-after by hunters in the 17th and 18th century — so much so, that their worldwide population may have been decimated to only about 2,000 individuals by the early 1900s.

Sea otters first became protected from the fur trade by the International Fur Seal Treaty in 1911. Now, sea otters in the U.S. are protected under the Marine Mammal Protection Act and the southern sea otter is listed under the Endangered Species Act as "threatened."

While sea otter populations increased after protection, there have been recent declines in sea otters in the Aleutian Islands (thought to be from orca predation) and a decline or plateau in the populations in California.

Other than natural predators, threats to sea otters include pollution, diseases, parasites, entanglement in marine debris, and boat strikes.