Weight From 15 to 30 pounds (6.8 to 13.6 kilograms) Special Feature Rich, dark brown coat of short, glossy waterproof fur that helps protect them even in ice-cold water Hear an otter (RealPlayer)   Click “Real Player” or “Windows Media” for video primers on river otter behavior.    Downloads: Real Player | Windows Media Eating River otters eat mostly fish, but they are not picky eaters and will also take crayfish, turtles, and other aquatic and amphibious animals. In clear water, swift-swimming otters hunt fish by sight. In murky water, they use their extremely sensitive facial whiskers.   Swimming Otters’ streamlined bodies, webbed feet, and long, powerful tails enable them to swim about seven miles (11 kilometers) an hour, faster than many fish. Otters close their ears and nostrils tightly when they submerge, which helps them stay underwater for as long as four minutes. Usually, though, they poke their heads out of the water every couple of minutes to get air.   Sliding River otters love to “let it slide”—the “it” being themselves. Seemingly a type of play activity, sliding is also a common winter mode of overland travel for otters. They bound several times to build up momentum, then belly flop onto slippery snow and ice, sliding several feet or more and reaching speeds of up to 18 miles (28 kilometers) an hour.