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November 21, 2017  |  Login

Sea Otter
Enhydra lutris

 
 
 
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What Are They Like?

One of the most charismatic of marine mammals, the sea otter is the largest and heaviest member of the weasel family. The sea otter’s cousins include other otter species as well as weasels, badgers and minks. Adult sea otters weigh between 75-100 pounds (34-45.4 kilograms), and are between 4.5 and 5 feet  (1.4-1.5 meters) long. Unlike other marine mammals, sea otters have no blubber to insulate them from the ocean’s cold. Instead, they rely on their extremely thick fur for insulation. A sea otter’s coat contains between 250,000 and a million hairs per square inch—the densest fur of any mammal. A sea otter’s coat is usually deep brown with silver-gray speckles. An adult otter’s head, throat and chest fur is lighter in color than the rest of its body. Male sea otters live between 10-15 years, and females live slightly longer with a lifespan of 15-20 years.

Where Do They Live?

Sea otters live in sheltered near-shore ocean waters of the Pacific Ocean from Mexico north to British Columbia. They live in waters 50-75 feet (15.2-22.9 meters) deep less than a mile from shore, and seek out areas that are protected from ocean winds and weather by rocky coastlines, kelp forests or barrier reefs.

 
Did You Know?
Otters have a range of vocal sounds that range from contented coos to grunts. When they are distressed or frightened, adult sea otters may whistle, hiss or even scream.

How Are Babies Made?

Sea otters breed in the fall, and males usually mate with multiple females. Mating takes place in the water, and can be a rough business. Mating males will bite the female on her muzzle, and sometimes hold her head underwater. Following a four-month pregnancy, female otters give birth to a single pup weighing between 3-5 pounds (1.4-2.3 kilograms). Mother otters nurse their young for up to 12 months, after which they begin to offer their pups bits of prey and teach them how to dive and find their own food. Young otters become independent at six to eight months of age.

What Do They Eat?

Sea otters consume more than 100 different prey species. They dive and forage for their food, which includes sea urchins, mollusks, sea snails and crustaceans. The otter’s fondness for sea urchins makes it an important “keystone” species in coastal ecosystems. Without sea otters to control urchin populations, the spiny creatures would decimate the Pacific’s kelp forests on which so much other marine life depends.

 
Did You Know?
Unlike other marine mammals, otters drink seawater. Their large kidneys allow them to extract fresh water, excreting the salt in concentrated urine.

What Do They Do?

Otters are one of just a few mammal species that are able to use tools. A sea otter can use a rock as a hammer to dislodge an abalone from the rocks on ocean floor. To open hard shells, it may pound its prey with both paws against a rock on its chest. An otter is also capable of using its paws to turn over underwater boulders in search of food. Sea otters use a loose pouch of skin that extends from their forelegs across their chest to store food collected on the ocean floor and bring it to the surface to eat while floating on their back. Otters use their front paws to tear their food apart and bring it to their mouth. Because it depends on its thick fur coat for survival, otters groom their fur carefully and frequently. Thanks to an incredibly supple skeleton, sea otters can reach and groom the fur on any part of their bodies.

How Concerned Should We Be?

The International Union for the Conservation of Nature (IUCN) lists the sea otter as “endangered.” By far the greatest threat to sea otters is the danger of oil spills. Because there are so few otters, and because they are concentrated in a fairly small range, an entire population could be wiped out by an offshore oil spill. When an otter’s insulating fur is covered with oil, it risks danger of death from hypothermia. If it doesn’t die of cold, an oiled otter risks death from kidney and liver failure when oil is ingested as it tries to groom its fouled fur. Hunting was once a serious threat to sea otters. They were once numerous in Pacific Ocean waters, with a world population numbering in the hundreds of thousands. Between the mid-1700s and the early 1900s, sea otters were hunted nearly to extinction for their thick and luxuriant fur coats. Worldwide otter populations had dropped to between 1,000 and 2,000 animals in 1911, when hunting of otters was banned.

What's Being Done?

The southern subspecies of sea otters, which live from Mexico north to the California-Oregon border, were listed as “threatened” under the Endangered Species Act (ESA) in 1972. They are also protected by California state law, and by the global Convention on Trade in Endangered Species (CITES), which prohibits international trade in the otters, or any part of their bodies including their fur. Sea otters also are protected under the Marine Mammal Protection Act. Many conservation groups, including the Monterey Bay Aquarium, Defenders of Wildlife, and Friends of the Sea Otter are working to protect the charismatic otter and its marine habitat. The hunting ban, conservation efforts, and reintroduction programs have helped sea otter populations rebound, especially in Alaska. Sea otters once again occupy about two-thirds of their former range.

 

Cute Baby Sea Otters at the Monterey Bay Aquarium

 
 
 
 
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