1. Male ducks have corkscrew-shaped penises.
2. Female ducks can keep the muscles in their vaginas taut so males' penises can't get in.
3. Female kangaroos have three vaginas.
4. Male rhesus macaque monkeys will "pay" to see female rhesus macaques' bottoms.
5. Nearly all bonobos are bisexual, and 75% of bonobo sex is not for reproduction.
6. Cat penises have spines or barbs made of keratin to scrape out competing sperm.
8. A male damselfly's tiny penis contains an even tinier spoon to scoop out leftover sperm from other males in the female's vagina.
9. In one species of elephant shrew, the end of the penis is spoon-shaped and contains a row of spines.
10. Elephant shrews are the only mammals, apart from primates and bats, that menstruate.
11. There's a tiny Australian mammal that has so much sex in a period of a few weeks that it basically disintegrates.
12. Female pandas only get excited ~sexually~ for a 24- to 72-hour window. It happens once a year at some point between February and May.
13. This is probably why artificial insemination is essential to the species' survival.
14. Male sharks have organs known as "claspers" rather than penises.
15. Female sharks have a cloaca, an opening that is used for both reproduction and getting rid of waste.
16. Male barnacles have one of the longest penises, relative to their size, of any animal – up to eight times their body length.
17. Water conditions dictate how a barnacle's penis develops. In calm water, it will grow long and flexible. But in rougher seas they grow a shorter, thicker one.
18. If a barnacle's penis isn't long enough, it can do something known as "spermcasting", in which it sends sperm out to sea for another barnacle to pick up.
19. Some sponges, molluscs, and corals spermcast too.
20. The sperm of deer mice swim in teams of up to 35.
21. But seven is the optimal number of deer-mice sperm to have in a team to reach the egg fastest.
22. During sex, flies create a buzz that can attract predatory bats.
23. Female lice of the genus Neotrogla have a penis and can have sex for up to 70 hours.
24. Ocelots tend to breed every other year.
25. Female squid don't have vaginas.
26. Most male squid don't have penises long enough to be useful. Instead, they propel sperm-containing capsules at females with one of their eight arms.
27. When a sperm capsule attaches to a female squid, she releases a hormone that dissolves her skin, allowing the sperm to get into her bloodstream.
28. The deep-sea squid Octopoteuthis deletron has sex with both males and females – whichever comes along first.
29. The Russian space agency is currently conducting experiments in space to see how microgravity affects sex for geckos.
31. At the end of sex, a male honey bee's genitals explode. They leave the tip of their penis in the female as a plug that stops the sperm falling out.
32. Male snakes have two penises, known as hemipenes. But they only use one at a time, and each snake hemipenis is associated with one testis.
33. Female snakes can store sperm for up to five years.
34. And if she mates with multiple males, a female snake can control which sperm she uses to fertilise her eggs.
35. Naked mole rats have misshapen sperm with abnormal heads.
36. Male anglerfish bite the females – who are much bigger – and fuse to them, sharing blood supplies. The males' fins and eyes melt away eventually, but they can keep producing sperm for their females for years.
37. Velvet worms have their genitalia on their head (bringing a whole new meaning to the term "mindfuck").
38. Elephants have a prehensile penis they can essentially use as a fifth leg.
39. An erect elephant penis can weigh as much as 30kg.
41. Some of the most common diseases dolphins get are STIs.
42. There's a YouTube video of a dolphin masturbating with a beheaded fish and you can watch it if you really want to.
43. Male dolphins that live in the Amazon river have been known to penetrate each other's blowholes.
44. Female bottlenose dolphins have used their bottle-shaped snouts as dildos on other females.
45. Dolphins have a prehensile penis.
46. As do tapirs.
47. Muskrats mate underwater.
48. Fennec foxes are monogamous and live in family units.
49. Female hyenas have something that looks like a penis but is actually a really long clitoris.
50. Echidnas have four-headed penises. Before ejaculation, two of the heads shut down, then semen comes out of opposite sides.
51. Chimps have penis spines that "improve stimulation" but can damage females during sex. :(
52. Seahorses are not actually monogamous.
53. Around a third of seahorse sexual encounters are same-sex.
54. Male penguin couples have been known to mate, build nests, and even look after stones, treating them as surrogate eggs.