Captive bottlenose dolphins are often observed. Most of the acts take place early in the evening or morning. There is repeated contact of the penis with the female's ventral region, then the male would approach the female from behind her, from a perpendicular angle, or some angle in between. Erection would occur suddenly, within one or two seconds. When intromission took place, two types of copulation were observed. In one, the penis was only inserted halfway into the vagina, and the act lasted no more than 10 seconds, though there were clear indications ejaculation had occurred. The second type consists of full penetration, and tends to last for 30 seconds. Pelvic thrusts are observed before, during, and after intromission, and the pattern is often repeated every one to eight minutes for one half hour or more, not always with the same female.
Young dolphins have been observed attempting to copulate with animals of both sexes, and also with sharks or turtles. They have also been observed attempting to masturbate with the aid of ropes or jets of water. This is common in captive dolphins, but masturbation is considered normal behavior in a great many terrestrial mammals as well.