Length: largest—giant otter Pteronura brasiliensis, up to 7.8 feet (2.4 meters); smallest—Asian small-clawed otter Amblonyx cinereus, up to 3 feet (0.9 meters)
Weight: largest—sea otter Enhydra lutris, males up to 95 pounds (43 kilograms); smallest—Asian small-clawed otter, up to 11 pounds (5 kilograms)
Life span: 15 to 20 years
Gestation: from 2 months for smaller species to 5 months for sea otters
Number of young at birth: 1 to 5, usually 2
Size at birth: 4.5 ounces (128 grams) for smaller species to 5 pounds (2.3 kilograms) for sea otters
Age of maturity: 2 to 5 years
Conservation status: four species, including the sea otter, are endangered; three otter species are vulnerable.
You can tell otter species apart by the
shape and amount of fur on their noses.
Unlike other marine mammals, sea otters do not have a layer of blubber to keep them warm; they rely on warm air trapped in their fur. Sea otters have the densest fur of any mammal, with about 100,000 hairs in a space about the size of a postage stamp!
Most otter species capture prey with their mouths, but Asian small-clawed otters and sea otters have flexible fingers and grab with their hands.
North American and European river otters have been known to share dens with beavers—but the beavers do all the building!
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Listen to a sea otter!
Listen to a Cape clawless otter pup at three months old!
Range: Africa, Asia, and parts of North America, Central America, and South America
Otters are the only serious swimmers in the weasel family. They spend most of their lives in the water, and they are made for it! Their sleek, streamlined bodies are perfect for diving and swimming. Otters also have long, slightly flattened tails that move sideways to propel them through the water while their back feet act like rudders to steer.
Almost all otters have webbed feet, some more webbed than others, and they can close off their ears and noses as they swim underwater. They can stay submerged for about five minutes, because their heart rate slows and they use less oxygen. They’re also good at floating on the water’s surface, because air trapped in their fur makes them more buoyant. Have you ever noticed that when an otter comes out of the water, its outer fur sticks together in wet spikes, while the underneath still seems dry? That’s because they have two layers of fur: a dense undercoat that traps air; and a topcoat of long, waterproof guard hairs. Keeping their fur in good condition is important, so otters spend a lot of time grooming. In fact, if their fur becomes matted with something like oil, it can damage their ability to hunt for food and stay warm.
Otters are very energetic and playful. You might say they love to party! They are intelligent and curious, and they are usually busy hunting, investigating, or playing with something. They like to throw and bounce things, wrestle, twirl, and chase their tails. They also play games of "tag" and chase each other, both in the water and on the ground. River otters seem to like sliding down mud banks or in the snow—they’ll do it over and over again! Otters also make lots of different sounds, from whistles, growls, and screams to barks, chirps, and coos. All this activity is part of the otters’ courtship, social bonding, and communication, and since otter pups need practice, they tend to be even more playful than the adults.
Life as a pup
Most otters are born in a den, helpless and with their eyes closed. The mother takes care of them, often chasing the father away after their birth, although in some species the dad may come back after a couple of weeks to help raise them. The babies, called pups, open their eyes and start exploring the den at about one month, start swimming at two months, and stay with their mother and siblings until they are about one year old, when they head off on their own.
For sea otters in their ocean habitat it’s a little different—the pups are born with their eyes open, and they have a special coat of hair so they can float, even though they can’t swim yet. They are carried on their mother’s stomach until they are about two months old, when they start swimming and diving on their own.
For most otters, social groups are made up of a mother, her older offspring, and her newest pups; the males spend most of their time alone or with a few other males. During breeding time or where there’s lots of food, though, larger groups of otters may gather, especially among sea otters in kelp beds.
Otter food may not all come from the ocean, but it is definitely fishy! River otters eat mostly fish, frogs, crayfish, crabs, and mollusks, with an occasional small mammal or bird. Sea otters eat many of the same things, but mostly sea urchins, abalone, crabs, mussels, and clams, which they crack open against rocks they hold on their stomachs. Otters have long, sensitive whiskers that help them find prey, even in murky water. Some species, like the Asian small-clawed otter Amblonyx cinereus, also use their hands to probe into mud or under rocks to find a tasty meal that might be hiding there. River otters use lots of energy and digest their food very fast, so they eat several times a day. Sea otters need to eat 20 to 25 percent of their body weight each day. That’s a lot of abalone! The otters at the San Diego Zoo are fed carnivore diet, carrots, and either squid or trout. They also get small amounts of "treats" for enrichment, like crayfish, worms, potatoes, or yams.