The cubs nurse until they are about 4 months old. They also learn how to swim and hunt by watching their parents. When the cubs are very young the mothers send the fathers out of the den. When the cubs are half grown, the fathers are welcome back into the den to help care for the young. River otters are often found playing together in the water.
Males are sociable most of the time except for during the breeding season.
During the breeding season, they will sometimes get in fights with other males. In winter, otters will make holes in the snow and also snowslide trails that are about 1 foot wide. In the summer, they leave slide marks along riverbanks. They often litter the trails with crayfish droppings. Otter tracks are about 3 inches wide.