A Eurasian river otter mother relaxes with with her two seven-month-old cubs on a shoreline in Shetland, U.K.
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- 2 to 6 feet long
- 10 to 75 pounds
The charismatic otter, a member of the weasel family, is found on every continent except Australia and Antarctica. Most are small, with short ears and noses, elongated bodies, long tails, and soft, dense fur.
There are 13 species in total, ranging from the small-clawed otter to the giant otter. Though most live in freshwater rivers, lakes, and wetlands, the sea otter and the smaller marine otter are found in the Pacific Ocean.
Habitat and young
Webbed feet and powerful tails, which act like rudders, make otters strong swimmers. Their nostrils and ears close to keep water out, and waterproof fur keeps them warm. They must carefully groom their fur and furry undercoat to keep them clean and sealed off to water, because they’re not covered in a fatty layer like other seagoing creatures. Otters have the densest fur of any animal—as many as a million hairs per square inch in places.
Otters also have particularly stinky poop, which even has its own name: spraints. It’s thought to get its special odor, which some scientists describe as smelling like violets, from the seafood diet otters eat.
Most otter species come ashore to give birth in dens, which sometimes have been used by other animals such as beavers. Sea otters are the exception, giving birth in the water. Baby otters, called pups or kittens, stay with their mothers until they’re up to a year old, or until she has another litter. River otters don’t breed until they’re at least five years old.
All otters are expert hunters that eat fish, crustaceans, and other critters. Sea otters have an ingenious method to open shellfish. A sea otter will float on its back, place a rock on its chest, then smash the mollusk down on it until it breaks open.
When it’s time to nap, sea otters entangle themselves in kelp so they don’t float away. They also sometimes intertwine their feet with another sea otter, so that they stay together.
River otters are especially playful, gamboling on land and splashing into rivers and streams. They learn to swim when they are about two months old, when their mother pushes them into the water.
Otters and their mustelid relatives were once hunted extensively for their fur, many to the point of near extinction. Despite regulations designed to protect them, many species remain at risk from pollution and habitat loss. The sea otter is listed as endangered on the IUCN Red List, pressured by pollution, pesticides, and conflicts with fishermen who kill them for eating their fish. Asian otter species also face threats from the illegal pet trade.