Like many marine mammals, including the whales, dolphin courtship and lovemaking are hardly private affairs. The rest of the gang always wants to join in – or at least have a good look. The bottle-nosed dolphin is broad-minded in its choice of sex partners. Males are frequently sighted copulating with turtles (they insert their penises into the soft tissues at the back of their victim’s shell), with sharks, and even with eels (when a dolphin’s penis is erect is has a hook on the end, and many a male will use it to hook a writhing, struggling eel). So it should be no surprise that males also copulate with each other, inserting their penises into each other’s genital slits. The Amazon river dolphin, or boto, sometimes goes further, penetrating another dolphin’s blowhole.

Text adapted in part from Dr Tatiana’s Sex Advice to All Creation