A male river otter appears to approach females indiscriminately until it finds one that is receptive. A male approaches a female and attempts to embrace her with his forelegs or rub and sniff her body. If she is receptive, the two roll and frolic; if not, she will push him away. Copulation is preceded by vigorous play - chasing, swimming, diving, twisting, cork-screwing, and lunging. In some species, the male bites the female's upper jaw or nose, in other species the male grasps the female by the scruff of the neck. Copulation takes place in the water, and lasts 10 to 30 minutes.
When a male sea otter finds a receptive female, the two engage in playful and sometimes aggressive behavior. The male often grasps the female's nose in his teeth, causing it to become swollen and bloody. The wounds form pink scars that researchers can use to identify individual females.