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Sea Otters

About AquaFacts: AquaFacts are a resource for students who are looking for information on the animals at the Aquarium or other Aquarium-related topics. Here, we’ve compiled some of the most frequently asked questions that we’ve received about sea otters. The answers come from our biologists and from reputable sources that we reference at the end of this page. If you have a question about sea otters that’s not addressed in this page or the references below, please feel free to email our librarian.

Sea Otters

Questions & Answers

Where do sea otters live?

Small sea otter populations inhabit kelp forests, bays and coastal waters near islands, reefs, and fjords in the North Pacific Ocean. In British Columbia, they are found along the windswept west coast of Vancouver Island and the central coast, near Bella Bella. The only sea otters near Vancouver are the four living at the Vancouver Aquarium.

How many sea otters are there?

There are approximately 5,000 sea otters in British Columbia. The population increase in B.C. has slowed in recent years because some parts of the population appear to be at equilibrium.

Russia: approximately 22,500
Alaska: approximately 71,500
California: approximately 2,500
Washington: approximately 550

Killer whales normally prey on pinnipeds. With the decline of pinnipeds, killer whales appear to have started eating sea otters, reducing the population in the Western Aleutian Islands, Alaska by 90% from 1992 to 1999. The population in the Aleutians is presently estimated at about 6,000 – 8,000 otters.

Have there always been sea otters in British Columbia?

Historically, yes, but the coastal habitat of sea otters made them easy targets for fur traders. During the 1700s and 1800s, sea otters were hunted to extinction along the B.C. coast. The current B.C. sea otters are descendants of 89 Alaskan sea otters that were relocated to the west coast of Vancouver Island from 1969-72.

Are all sea otters endangered?

No, but some sea otter populations are endangered. The B.C. sea otter population was downlisted to threatened in 1996 by the Committee of the Status of Endangered Wildlife in Canada and through the B.C. Wildlife Act. They are protected by the federal government’s Canada Fisheries Act, and the BC Wildlife Act. The California population is protected by the Marine Mammal Act and the U.S. Endangered Species Act. Alaska’s Southwestern/Aleutian population is being considered for listing as threatened.

What are the differences between a sea otter and a river otter?

Sea otters are found only in the ocean and are rarely seen on land. River otters swim in rivers, streams and the ocean. They often come on shore. A sea otter’s tail appears much shorter (approximately 1/3 the length of its head and body) and flatter than a river otter’s (roughly 2/3 the length of its head and body). Sea otters have paddle-shaped hind limbs, whereas the river otters have webbed paws. Sea otters spend a lot of their time floating on their backs—they rest, groom and eat in this position. River otters do not. Sea otters are commonly seen in large groups, while river otters rarely occur in groups larger than a single family which may include 3-4 young. Sea otters usually have a single pup, born in the water. River otter pups (3-4 in number) are born on land.

sea-otter-inquisitive.jpgsea-otter-river-otter.jpg

 

 

 

Sea Otter vs River Otter

What do sea otters eat?

Sea otters eat a seafood smorgasbord: clams, mussels, chitons, snails, prawns, crabs, abalone, sea urchins, squid, sea star legs and in some areas, several species of fishes. Sea otters use their sense of touch to find food; diving sea otters feel for food along the ocean floor with their sensitive front paws. They have poor underwater vision. Sea otters dine floating on their backs, using their stomachs as a table to spread out the food they have gathered. They may use rocks to crush hard-shelled food, like clams. Sea otters eat a huge amount of food (up to 30% of their body weight) every day. They need a lot of “food energy” to maintain a constant body temperature in their cold water habitat; they have no body fat to insulate them like other marine mammals so instead their fur is what keeps them warm. Their metabolic rate is 2 or 3 times that of similar-sized land mammals.

What do you call a group of sea otters?

Sea otters often rest in groups called “rafts”. Rafting sea otters sometimes hold paws to stay together. Sea otters segregate by sex. Groups of females and their pups tend to stay in the centre of their range, territorial breeding males stay close to the female groups, and sub-adult male groups are seen on the outskirts of the range. These sub-adult males are the first to move into new areas when they become available. Male rafts are made up of all ages of males in non-breeding season.

Are sea otters always in the water?

Sea otters mate, sleep, groom, hunt, give birth, rest and play in the ocean! In some areas, usually where there are few predators, sea otters will rest on land, but they spend most of their time at the water’s surface floating on their backs. Sea otter pups are born in water and float like corks, but they cannot swim for several weeks. A sea otter mother carries her pup on her stomach, and spends much of her day caring for her baby: feeding, protecting, teaching, and grooming. Perhaps this is why females typically have one pup at a time.

sea-otter-on-back.jpgsea-otter-with-pup.jpgsea-otter-raft.jpg

How thick is a sea otter's fur?

Sea otters have one of the thickest fur coats in the animal kingdom. An adult pelt contains between 800 million to one billion individual hairs (roughly 100,000 or more per square cm). Their fur is composed of two types of hair: long, sparse guard hair and soft, dense underfur, or pile hair. Sea otters depend on their fur to keep them warm because they have no insulating fat layer. It is critical that sea otters keep their fur clean to maintain the insulating air layer between the water and their skin. Adults spend 30 percent or more of their day grooming their fur by licking and blowing into it. At birth, a newborn sea otter’s coat, called a lanugo, acts like a life preserver and keeps the baby floating at the water’s surface. It takes at least two months before the “extra-buoyant” lanugo is fully shed. Only then can the pup dive.

Did you know oil spills are the greatest threat to sea otters?

Sea otter fur loses its buoyancy and insulating capacity when covered with oil. This leads to hypothermia and pneumonia. When sea otters groom and clean their oiled fur, they ingest and inhale oil. This has detrimental effects on their liver, kidneys and lungs.



Facts & References

Key Facts

  • Sexual maturity: males - 6 years; females - 4 years.
  • Length of pregnancy (gestation period): 6 to 9 months - can be longer if “delayed implantation” occurs. This is when the egg is fertilized, but doesn’t implant into the uterine lining right away. Instead, the fertilized egg enters a state of “suspended animation” for up to three months.
  • Pupping season: spring and early summer, but may occur throughout the year.
  • Length: males - 1.5 m; females - 1.4 m; 
  • Weight: males - up to 45 kg; females - up to 32.6 kg.
  • Average life span: males - 10 to 15 years; females - 15 to 20 years.

Did You Know?

  • A healthy sea otter’s skin never gets wet because their fur is so dense.
  • River otters, weasels, and badgers are sea otter relatives (Family Mustelidae).
  • Sea otters dive frequently for food; a typical dive is 30 m deep and lasts 45-127 seconds.
  • Large complex kidneys make it possible for sea otters to drink a bit of salt water, although most of their fresh water intake comes from their food.
  • Predators include killer whales, sharks, and sea lions: bald eagles prey on pups.
  • They are one of the few tool-using mammals; sea otters use rocks to break open their food.

References 

  1. Doroff, Angela M, Estes, James A., Tinker, M. Tim, Burn, Douglas M. and Evans, Thomas J. 2003. “Sea Otter
  2. Population Declines in the Aleutian Archipelago” Journal of Mammalogy 84(1):55-64.
  3. Enhydra lutris Fact Sheet. Oceanlink. (http://oceanlink.island.net/oinfo/otterpage/otter.html)
  4. Smithsonian Institute. “Useful References on Polar Bears and Marine & Sea Otters.” Smithsonian Encyclopedia. [online bibliography] 

Permission is granted by the Vancouver Aquarium Marine Science Centre for classroom teachers to make copies for non-commercial use. This permission does not extend to copying for promotional purposes, creating new collective works, or resale.

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