The only way to determine a dolphin's gender in the wild is to see a clear view of their genitals, or to observe an erection, act of intercourse, or a baby swimming close to an adult presumed to be a female. Males have two slits that look similar to an exclamation point. The long anterior slit houses the genital region, while the smaller posterior slit houses the anal region. Two small pores are present on either side of the genital-anal slit, which have been considered possible vestigial nipples. Females have one continuous slit which houses both the anal and genital openings, the anus being towards the posterior.
Females also have a set of slits housing the mammary glands.
These slits flank either side of their genital slit. Occasionally females will have extra false sets of mammary slits. These extra slits are generally non-functional and could be a hold over from the dolphin's terrestrial ancestor. There is no actual mating season for dolphins. They mate 365 days a year.