Otters living on the shores of the Great Lakes also eat lampreys. Lampreys are eel-like fish that suck blood from sports fish. The otter eats clams, crayfish, frogs, toads, snakes, beetles, snails, worms, and bird eggs. The river otter has been known to break holes in beaver dams so that the water will flow out and leave stranded fish. There is no evidence it ever attacks the beavers.
River otters make many sounds including a whistle for long-range calling.
They chatter during mating season, softly chuckle or chirp to show affection to family members, and grunt and growl at intruders.