They are aquatic mammals generally living along rivers, as their name implies, but they’re also found near streams and lakes. Otters prefer water bordered by woods and with wetlands, such as marshes nearby. They usually take over abandoned dens made by other animals such as beavers.
Generally active at night, river otters often sun themselves on rocks or riverbanks during the day.
Flexing their long bodies up and down, paddling with their webbed hind feet, and using their feet and strong tails to steer, river otters are underwater acrobats. They can stay underwater for up to four minutes, after which they must surface to breathe. As they dive, they close their ears and nostrils to keep water out. They hunt underwater, skillfully chasing fish, their main food. Otters grab their prey in their mouths. They eat small fish that they catch right in the water, holding the food with their forepaws while floating on their backs. When the otters catch large fish, they haul them onto shore to dine. They eat mainly fish, plus crayfish, frogs, salamanders, snakes, clams, snails, turtles, birds, and insects.
Female river otters give birth in the spring. Babies are born blind and stay in the den until they’re about one month old. When they are several weeks old their mother coaxes them into the water and they learn to swim.