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.

African Cape clawless otter. The name otter is derived from Old English and Indo European root words that also gave rise to the English word for water.

Almost all otters have webbed feet, some more webbed than others, and they can close off their ears and nose as they swim underwater. They like to swim on their back and sides and can see just as well underwater as they can above. Otters can stay submerged for five to eight minutes, depending on the species, because their heart rate slows, and they use less oxygen. Sea otters are good at floating on the water’s surface, as air trapped in their fur makes them more buoyant. They are much more buoyant than river otters, which have to actively swim to keep afloat.

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.

An otter’s rounded nose has whiskers above the lips that detect water current changes as well as the presence of prey or potential predators lurking in the water. And what do otters have to fear? It depends on where they live. Giant otter young are vulnerable to large cats, anacondas, and caimans. Sea otters face predation by killer whales, sea lions, and sharks. Small-clawed otters are often killed by domestic dogs. Juvenile spotted-necked otters are prey for fish eagles and monitor lizards. Other otter species must watch out for birds of prey and crocodilians.

River otters sliding across snow in Yellowstone.

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.

Otters make lots of different sounds, from whistles, growls, and screams to barks, chirps, moans, and coos. River otters scent mark by using paired scent glands near the base of their tail. These glands produce a strong, musky odor. The scent markings are believed to delineate territorial boundaries and communicate information concerning individual identity, sex, sexual state and receptivity, and time elapsed between scenting visits. This marking behavior looks playful, as the otters rub on logs, roll in piles of fallen vegetation, or grab armfuls of leaves on bushes and trees to rub on their chest and legs, but it has a serious communication purpose in the otter world. Urinating or defecating in the same place is also used as a form of communication. Eurasian otter males form a dominance hierarchy, with the highest-ranking animals occupying the most favorable ranges and marking them accordingly.

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