1

An octopus's penis breaks off during sex and grows back in time for the next mating season.

2

Male hippopotami defecate while spinning their tails to splatter feces on and around the females (see associated, purposefully grainy GIF). This really gets female hippos in the mood.

3

The manakin bird's mating dance includes a moonwalk.

4

Male hooded seals attract mates by blowing large pink bubbles out of their noses.

5

The Silverback gorilla has a 1.5 inch penis (~4 inches if measured from the tailbone).

6

The male bowerbird builds a hut made of twigs and then decorates it with hundreds of items--all in coordinated colors. If the female likes the aesthetics of his bachelor pad, they mate there.

7

bonobos use sex for mating as well as for resolving conflict, trading goods and favors, deciding social status, reducing stress, and just because.

8

Elephants are only capable of getting pregnant every 4 to 9 years, and are pregnant for 22 months before giving birth. As a result, they usually only have one offspring in their lives.

9

When a honeybee climaxes, his testicles explode and he dies.

10

16% of sexual encounters between praying mantises include the female eating the male's head during sex.

11

Litters of kittens can contain all different types of kittens because the female cat can get pregnant while she's already pregnant.

12

There are no male whiptail lizards. Whiptail lizards dry-hump each other to stimulate the production of eggs that are clones of themselves.

13

The female anglerfish absorbs the mating male anglerfish into her body.

14

Competition between male Galapagos giant tortoises over female affection consists solely of a height contest. The shorter male walks away sexually frustrated while the taller male will nip at the female's legs until she retracts them, rendering her immobile/mate-able.

15

Worker ants are all female, but the queen ant needs sperm from a male to make another queen, so when it's time for a new queen she'll birth so many male ants that the females can't kill them all (though they'll try). The queen ant will then have incest with a surviving male, making a new baby queen (just like a real royal family).

16

The female cichlid carries her eggs in her mouth until they hatch.

17

Male argentine lake ducks have a (roughly) 17-inch, corkscrew-shaped penis that they sometimes use to lasso females trying to escape. And most duck mating is rape. And ducks are necrophiles. And cannibals.

18

Male argentine lake ducks have a (roughly) 17-inch, corkscrew-shaped penis that they sometimes use to lasso females trying to escape. And most duck mating is rape. And ducks are necrophiles. And cannibals.

19

The male seahorse gives birth.

20

When a male camel is ready to mate, he pukes up a pink sac (called a "doula") that hangs from the side of his mouth, and he begins to drool excessively. Female camels find this all very attractive.

21

Flatworms have both male and female organs. When they mate, they "sword-fight" with their penises: The one that gets stabbed first has to be the mom.

22

A dolphin's penis is retractable like turtle's head and prehensile like a human's thumb. They often use their penises to explore objects the way humans would use their hand.

23

Male porcupines urinate on female porcupines before mating.

24

Red-sided garter snakes mate through massive snake-bangs called "breeding balls" wherein one female takes on more than a hundred partners.

25

Hermaphroditic sea hares mate in chains, acting as male to the one in front and female to the one in back.

26

During mating, the male bedbug stabs his sabre-like penis through the female bedbug's abdomen. At one abusive relationship per season, you can tell how old a female bedbug is based on the number of scars on her abdomen.

27

The male Darwin Frog incubates around 30 eggs in his mouth while they grow and hatch.