1. Male anglerfish fuse irreversibly with female anglerfish during sex. Spyder24 / Getty Images In order to reproduce, the "sexually parasitic male" attaches itself to the female's belly. Their circulatory systems then connect, and the male slowly dissolves. You can see a picture here. 2. Cat penises have spines. Tap to play or pause GIF Tap to play or pause GIF giphy.com Or as this paper on Penile Spines of the Domestic Cat states: "The glans penis of the male cat is covered by relatively large, pointed, horny spines". 3. Male rhesus macaque monkeys will "pay per view" to see the bottoms of the female rhesus macaque monkeys. Donyanedomam / Getty Images A study showed that "male rhesus macaques sacrificed fluid for the opportunity to view female perinea and the faces of high-status monkeys but required fluid overpayment to view the faces of low-status monkeys." 4. Anacondas breed by forming "breeding balls" – multiple males wrap around a female and attempt to mate. Tap to play or pause GIF Tap to play or pause GIF CBA / youtube.com On Audible's Zoopedia, Sue Perkins explains: "This process lasts for up to a month. Females can be several times the size of their mates. This means that larger male snakes are occasionally mistaken for females and find a knot of snakes forming around them." 5. Alligators have permanent erections. Nattanan726 / Getty Images Watch a video here. 6. A male giraffe drinks the female's urine to check if she's ready to mate. Tap to play or pause GIF Tap to play or pause GIF National Geographic It's called the Flehmen Sequence. Watch a video here. 7. A male honey bee leaves the tip of its penis in the female after sex. Tap to play or pause GIF Tap to play or pause GIF Cartoon Network You can watch a video of it here. 8. Bonobos use sex for more than just reproduction. Uso / Getty Images Researchers believe that Bonobos use sex to resolve disagreements – and that "nearly all" Bonobos are bisexual. 9. The antechinus is a tiny Australian mammal that has sex for up to three weeks solid, then disintegrates. Quentin J. Lang / Getty Images This type of activity is called semelparity – which means sex happens once in a lifetime. National Geographic writes: "This burst of speed-mating is his one chance to pass his genes on to the next generation, and he will die trying. He exhausts himself so thoroughly that his body starts to fall apart. His blood courses with testosterone and stress hormones. His fur falls off. He bleeds internally. His immune system fails to fight off incoming infections, and he becomes riddled with gangrene." 10. Snakes have two penises, and alternate which one they use when mating. Tap to play or pause GIF Tap to play or pause GIF Warner Bros. But if they have a choice, they like to use their right penis, according to this study. 11. Adders sunbathe before sex to warm up their genitals and to help produce sperm. Tap to play or pause GIF Tap to play or pause GIF Disney 12. The male capuchin monkey covers himself in urine to show that he's keen to mate. Cameris / Getty Images On Audible's Zoopedia, Sue Perkins explains: "Unlike with some primate species, it’s not visually obvious when the female capuchin is ready to mate – so she has to take the initiative herself. This usually involves getting the attention of a male by shaking branches and throwing stones at him while pouting." "The male communicates his social and sexual status to the females by [washing] himself in urine. The exact reason for this behaviour is still disputed but it’s probably part of some sort of chemical or pheromone signalling." 13. Female Chinese fruit bats turn themselves upside down to fellate the male bat while having sex. Tap to play or pause GIF Tap to play or pause GIF giphy.com Researchers believe it could help with fertilization. "Sexual encounters that involved oral stimulation lasted, on average, 100 seconds longer than those that didn't, something that could be conducive to fertilization." 14. The female whiptail lizard can clone herself. Tap to play or pause GIF Tap to play or pause GIF Space / BBC America 15. Female ducks have corkscrew vaginas, and they can send a duck penis down a "dead end" if the male forces copulation. Bassador / Getty Images Find out more here. 16. And alligators seduce mates by bellowing from the water. Tap to play or pause GIF Tap to play or pause GIF giphy.com On Audible's Zoopedia, Sue Perkins explains: "Their mating season tends to be in the spring, when they gather in large numbers and bellow together – causing infrasonic waves that make the water around them to ‘sprinkle’ – these are called ‘alligator dances’ – which is a surprisingly sweet name for what is essentially a gathering of horny killers." "The courtship itself can take up to a month, with the male seducing a specific female with purring vocalisations called ‘chumpfs’ and by lifting his head out of the water."