Bottlenose Dolphins Caught in the Act!
By Lloyd Edwards

Monday, 5th December 2022

During our 25 years of running marine cruises in Algoa Bay, Raggy Chances have seen Indo-Pacific dolphins on around 98% of cruises. Quite remarkable and a good reason to be named the “Bottlenose Dolphin Capital of the World”, which we proclaimed in 2016.

During most of these encounters, we have observed the dolphins mating on the surface. In fact “Lover’s Lane” at St Croix Island derives it’s name from this activity. They seem to prefer mating in shallow water, as there is less chance of a shark attack while their thoughts are on other issues!

As they lack appendages to hold one another, a male will “press” the female against the surface of the water during belly to belly copulation. Because they are of a similar size, males cannot overpower females and become aggressive prior to mating. Tooth rake marks are often observed on their bodies, which probably occurred as a result of mating behaviour. After successful copulation, a male often breaches clear of the water ,with his penis still erect and protruding from the genital slit, as seen in the attached images.

While copulation for sexual reproduction only lasts for up to ten seconds, social sex, which is used to maintain social bonds, may last a whole lot longer and more often. This could involved both heterosexual and homosexual behaviour. The homosexual behaviour can begin early in life and these bonds will be used to “hunt” females together in later life. They will also restrict the movement of females until they become receptive and can be mated with. This also involves protecting their harems from other marauding males and can become violent.

While humans are not the only animals to have sex for pleasure, it has also been observed in Bonobos and certain bat species. It is a fact that dolphins mate for pleasure because they copulate all year round, including during months when they cannot conceive.

Recent studies have revealed that for her size, a dolphin has a very large clitoris (the size of a penlight AA battery), which has erectile tissues and can be filled with blood. It also contains large nerves which increase the sensitivity and thus becomes more of a pleasure than mere reproduction. It is also known that the clitoris changes shape as the female becomes an adult, which suggests that it has a function related to sexual maturity.

Another amazing adaptation is that the female’s vagina is intricately pleated, which can easily stop the penetration of a penis. She can therefore choose which males sperm she wants to fertilise her egg.

With regards sex in other cetaceans, a pleasurable clitoris may be less useful in species where males and females interact less often, like Sperm whales.