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.
The otter mainly eats aquatic animals such as plankton and fish, but the otter also hunts small amphibians, birds and occasionally small mammals.
The word otter derives from the Old English word otor or oter. This, and cognate words in other Indo-European languages, ultimately stem from the Proto-Indo-European language root *wódr̥, which also gave rise to the English word “water”.
Otters have long, slim bodies and relatively short limbs with webbed paws. Most have sharp claws on their feet and all except the sea otter have long, muscular tails. The 13 species range in adult size from 0.6 to 1.8 m (2.0 to 5.9 ft) in length and 1 to 45 kg (2.2 to 99.2 lb) in weight. The Oriental small-clawed otter is the smallest otter species and the giant otter and sea otter are the largest. They have very soft, insulated underfur, which is protected by an outer layer of long guard hairs. This traps a layer of air which keeps them dry, warm, and somewhat buoyant under water.
Have you ever noticed that when otters come out of the water, their outer fur sticks together in wet spikes, while the fur underneath still seems dry? That’s because otters 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.
The only continents without otters are Australia and Antarctica, and the only habitats they do not live in are deserts, polar regions, and mountains. The most widely distributed otter is the Eurasian otter, found throughout Europe, North Africa, and Asia to Japan and Indonesia. Typical otter habitat includes both water and land, except for the sea otter, which rarely comes ashore. Otter species except the sea otter live in dens, most made by other animals, such as beavers. They can also live on rocks or driftwood. The sea otter from North America have been tracked journeying as far as southern Japan.
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 otter groups 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, fish, octopuses, mussels, and clams. They crack open clams and mussels with rocks they hold on their stomach—the only otter species to use rocks as tools.
Otters have long, sensitive whiskers that help them find prey, even in murky water. Some species, like the Asian small-clawed otter, 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 nearly a third of their body weight each day. That’s a lot of abalone!
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. Otters like to throw and bounce things, wrestle, twirl, and chase their tail. 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! All this activity is part of the otters’ courtship, social bonding, and communication behavior, and since young otters need practice, they tend to be even more playful than the adults.