Sea Otter
Enhyrda lutris
Adult sea otter - 13

E. lutris

Physical Attributes

Height and Weight

The sea otter is the heaviest member of the Mustelidaes [8]. The average male sea otter weighs between 49 and 99 lbs and range in length between 4 and 5 feet. Females are smaller and weigh between
Sea otter swimming in a kelp forest -11
30 and 73 lbs and measure 3 to 4.5 feet in length [4].

Other Basics

Sea otter’s have webbed feet. Unlike most animals their fifth digit is the longest, which allows them to reach greater speeds while swimming. However this hinders their movement on land. They swim with both their feet and their muscular tail and are able to reach speeds of 5.5 mph. Sea otters are able to drink sea water due to their large kidneys. Sea otter’s excrete the sea water as a concentrated form of urine. They also have large lung capacity that allows the otters to dive and forage for food underwater as well as help their buoyancy when resting. Sea otters also have a pouch that extends across their midsection that allows them to hold tools and prey during hunting [3][5].


One of the sea otter’s most unique physical attributes is its fur. Since the sea otter has no blubber it must rely on its fur for protection from the cold environment they live in. Sea otter’s have the densest fur of any animal in the animal kingdom with one million strands of hair for every square inch. The coat consists of two layers of fur. The top layer of fur has long waterproof hairs that keep the coat underneath dry from water. The top layer must be groomed/cleaned constantly in order for the fur to retain its waterproof quality. The undercoat consists of shorter hairs and keeps the sea otter’s body warm. The fur also traps air, which increases the buoyancy of the sea otter. Sea otter’s don’t molt but rather gradually shed and replace their fur throughout the year. The fur can range from light brown in color to black, with the face usually a lighter color in adults [3][5][9].

Hunting & Diet

Sea Otter eating a clam - 14

Sea otter’s have a high metabolic rate and must eat around 30% of their body weight a day. This is due to the fact they expend a lot of energy keeping their bodies warm from their cold environment. This requires the Sea otter’s to be diurnal, which means they hunt twice a day. They hunt once in the morning before sunrise and then again in the afternoon. If food is scarce they hunt again at midnight. They spend roughly 25-60% of their day hunting depending on food scarcity [5].

Sea otter’s hunt during short dives to the bottom of the sea floor, these dives last between 1 and 5 minutes. They catch fish with their forepaws as well as other prey. Sea otter’s are excellent foragers as they can use their forepaws to overturn boulders to seek out prey. Another unique attribute to sea otters are their ability to use tools. They often use rocks to dislodge and break open prey [8].

Their diet consists of a large variety of species. Primarily they eat marine invertebrates including bivalves (i.e. mussels and clams) and mollusks (i.e. snails). Sea otter’s are not limited to these but have been known to also catch fish and larger animals such as octopus [3].

Sea otter’s are a keystone species. A keystone species is defined as a species that has a much larger impact on their ecosystem than their population size
Range of sea otters - 7
indicate. Their status as a keystone species is directly tied to their diet, as they feed on sea urchins. Sea urchins eat kelp causing it to dislodge from its holdfast and die. Kelp is crucial to the local ecosystem thus the sea otters help preserve the ecosystem for themselves as well as other inhabitants of kelp forests [10].


Sea otters live primarily on the western coast of the United States extending from California to Alaska as well as the northeast coast of Russia (more specifically around the Kuril islands). Sea otters live close to the coast, generally they stay within one mile from shore. They prefer protected coastline such as rocky coasts, reefs and kelp forests. Sea otters also live in waters that average between 50 and 75 feet deep [5].

Social Behavior

Sea otters hunt individually but they aren’t a totally independent species. When resting sea otters form linked single-sex groups, which are called rafts. The average raft contains between 10 and 100 sea otters. Male rafts are typically larger than female ones. These rafts help them from drifting out to sea when sleeping. Otters may also wrap themselves in kelp for the same reason [6].

Male sea otters can have territory
A small raft - 11
times of peaked reproduction males protect their territory from other males ensuring a higher success rate of finding a mate. Fighting is rare between sea otters though. Males that don’t have territory can be found with other male sea otters. Females don’t carve out their own territory but are allowed to freely roam between territory boundaries [5].


There are currently 107,000 estimated sea otters worldwide [8]. Sea otters have an average lifespan of 10-15 years for males and 15-20 years for females. Sea otters have multiple partners but pairs stay together for a couple of days during the initial reproduction. Mating takes place in the water and is peaked during spring and autumn. Males often bite the female’s nose and hold them underwater during mating. Sea otters breed between once or twice every two years. Females are pregnant between four and twelve months before giving birth. Newborn pups weigh between 3 to 5 lbs [1]. Only 25% of pups survive through one year, with most moralities coming during the winter. Nursing ends and independence begins for pups after six months [7]. Sexual maturity for males occurs at 5 years and at 3-4 years for females [5].


Sea otter covered in oil -15

Sea otters are currently an endangered species. Their predators include sharks, sea lions, eagles, orca whales, bears and coyotes. Predation of sea otters is uncommon, though the increasing local shark populations are increasing predation. The biggest historical threat to sea otters has been the fur trade. Since their fur is so dense and luxurious sea otters have been hunted for their pelts to near extinction. Sea otters have since been protected by the Treaty for the Preservation and Protection of Fur Seals that was signed in 1911. This treaty has allowed the sea otter population to rebound. Their thick fur is also susceptible to oil spills. The oil sticks to their fur and retards the ability for them to retain heat causing them to die to too much exposure to the cold. During grooming the sea otters also ingest some of the oil, which is also harmful [7]. Due to the sea otter’s habitat they can be infected by parasites. The parasite Toxoplasma gondii is often fatal and is transmitted to sea otters from domestic cat and opossum droppings that infiltrate coastal waters from rain runoff [2].

Works Cited
  1. "ARKive - Sea Otter Videos, Photos and Facts - Enhydra Lutris." ARKive - Discover the World's Most Endangered Species. <>.
  2. "NOAA Magazine Online (Story 72)." NOAA Magazine. <>.
  3. "OTTERS - Diet & Eating Habits." SeaWorld/Busch Gardens ANIMALS - HOME. <>.
  4. "Sea Otter (Enhydra Lutris) - Animals." A-Z Animals - Animal Facts, Information, Pictures, Videos, Resources and Links. <>.
  5. "The Sea Otter (Enhydra Lutris): Behavior, Ecology, and Natural History." Welcome to the USGS Fort Collins Science Center. <>.
  6. "Sea Otter Facts." TASSC: Home. <>.
  7. "Sea Otter Frequently Asked Questions - Defenders of Wildlife." Defenders of Wildlife - Protection of Endangered Species, Imperiled Species, Habitats. <>.
  8. "Sea Otters, Enhydra Lutris at" - Marine Biology, Ocean Life Conservation, Sea Creatures, Biodiversity, Oceans Research... <>.
  9. "Sea Otters, Sea Otter Pictures, Sea Otter Facts - National Geographic." Animals - Animal Pictures - Wild Animal Facts - Nat Geo Wild - National Geographic.. <>.
  10. "Exploring Nature Educational Resource." Exploring Nature Educational Resource: A Natural Science Resource for Students and Educators. Web. 28 Nov. 2011. <>.
  11. | Ocean Wildlife Nature Pictures | Stock Photo Agency. <>.
  12. "Sea Otter." Wikipedia, the Free Encyclopedia. <>.
  13. Whale Watching Victoria, BC and Vancouver Island | Eagle Wing Tours | Orcas and Killer Whales. <>.
  14. Phillip Colla Natural History Photography :: Online Photo Search." Natural History Photography. <>.
  15. Shell Executives Accuse Oil-Covered Otter Of Playing It Up." The Onion - America's Finest News Source. Web. 29 Nov. 2011. <,2818/>.