Aristotle was one of the first great thinkers to argue that dolphins, who sleep with their blowholes above the water, are mammals. The ancient Greek philosopher had noticed that, like humans, dolphins "copulate and are viviparous," meaning that they give birth to live young.
Many years later in 1945, an influential paleontologist by the name of George Gaylor Simpson wrote that "the cetaceans on the whole are the most peculiar and aberrant of mammals—" dolphins included. Simpson claimed that the dolphin's evolution happened as a result of their opportunism, not some fated or fixed plan.
But it wasn't until the 1960s when scientists realized that dolphins didn't just evolve to reproduce like humans; rather, these warm-blooded, opportunistic cetaceans are also equipped with similar organs and urges that drive them to have sex for pleasure.
Male Dolphins Pleasure Themselves Using Eels And Dead Fish
As a matter of fact, dolphins are one of the few animals who have sex for pleasure - a discovery made based on observations that dolphins copulate year-round, including during months when they cannot conceive. Furthermore, female dolphins have clitorises with erectile tissues and nerve bundles, and scientists have yet to determine if this piece of their anatomy serves a reproductive function beyond pleasure.
In the words of George Gaylor Simpson, "What can happen does happen." And dolphins do seem to take advantage of the pleasure their anatomy offers - whether they are copulating with a partner or stimulating themselves. In fact, bottlenose dolphins have been observed wrapping live eels around their members to pleasure themselves. They’ve also been filmed using a decapitated fish head for the same purpose.
Male Dolphins Have Members That Can Swivel And Grasp Like A Hand
A dolphin's body is uniquely adapted to life underwater; at about 65 meters under, the pressure of the water above them triggers their lungs to collapse and their bodies to shrink. By becoming more compact, they can easily forage and go about their business in deep waters without floating to the surface.
Like the rest of their body, a male dolphin's penis also evolved to make copulating underwater as simple as possible. Dolphins have a prehensile penis that they can extend, retract, manipulate, and grasp onto their partner to stay connected during the act.
Dolphins Sometimes Try To Mate With Humans
In 2002, a 400-pound bottlenose dolphin named Georges caused a stir in the beachside community of Weymouth, England. It was reported that the "sexually aggressive" dolphin showed an "unhealthy interest" in people who were diving in the harbor. Not only was Georges attempting to harm himself by swimming into boat propellers, on numerous occasions, he also tried to mate with divers.
"When dolphins get sexually excited, they try to isolate a [human] swimmer, normally female. They do this by circling around the individual and gradually move them away from the beach, boat, or crowd of people," said dolphin trainer Ric O’Barry, famous for training TV’s Flipper. O'Barry also warned that the Georges posed “a real threat to the thousands of swimmers who will be descending on Weymouth over the summer” because the unwanted attention could easily cause people to drown.
Fortunately, no one was hurt.
They Occasionally Practice Inbreeding
In 1993, researchers took interest in a male dolphin known as BJA when they discovered he had reproduced with his own 15-year-old daughter. As it turns out, this wasn't an isolated occurrence; the researchers also found that several males in BJA's pod had forcefully copulated with their mothers.
Later in 2004, another group of researchers used human paternity tests to prove that dolphins occasionally inbreed and will sometimes share a sexual partner with their sibling. That said, there is evidence that inbreeding in dolphins may primarily occur in some parts of the world where dolphins exhibit limited dispersal, meaning that they are more restricted in their ability to travel beyond their home range to find partners.