12 Animal Sex Facts You Didn't Want to Know

If you like to tune in to TMZ to catch up on the latest celebrity sex scandals, imagine what you're missing by not watching Discovery or National Geographic instead: the details of animal mating can be titillating, amusing, and just plain weird all at the same time.

Male Alligators Have Permanent Erections


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Penises vary widely across the animal kingdom, but a universal theme is that this organ somehow changes size or shape before or during the act of mating, then reverts back to its "usual" configuration. Not so for alligators, the males of which are endowed with permanently erect penises (layered with numerous coats of the stiff protein collagen) that lurk inside their cloacas, then burst out suddenly like the baby Alien from John Hurt's stomach. Perhaps even more weirdly, the six-inch-long penis of an alligator isn't everted by muscles, but by the application of pressure on its abdominal cavity, clearly an essential bit of reptilian foreplay.

Female Kangaroos Have Three Vaginas

Kasngaroo with joey laying down

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OK, admit it: your first thought on reading this headline was, "how in the world do male kangaroos choose the right one?" The answer to this conundrum is that, whereas female kangaroos (and all other marsupials, for that matter) possess three vaginal tubes, they only have one vaginal opening, thus eliminating any confusion on the part of their mates. When males inseminate females, their sperm travels up either (or both) of the side tubes, and about 30 days later the tiny joey travels down the central tube, from which it slowly makes its way to its mother's pouch for the remainder of its gestation.

Antechinus Males Copulate Themselves to Death

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Antechinus, a tiny, mouselike marsupial of Australia, would be almost completely anonymous except for one odd fact. During their brief mating season, the males of this genus copulate with females for up to 12 hours straight, stripping their bodies of vital proteins in the process and even dismantling their own immune systems. Shortly afterward, the exhausted males drop dead, and the females go on to bear litters with mixed paternity (that is, different babies have different fathers). The moms live a bit longer—after all, they have to nurture their young—but they, too, usually die within the year, only having had the opportunity to breed a single time.

Flatworms Fence With Their Sex Organs

Flatworms fencing
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Flatworms are among the simplest invertebrate animals on earth, lacking well-defined circulatory and respiratory organs and eating and pooping via the same body opening. But all bets are off during mating season: hermaphroditic individuals, which possess both male and female sex organs, sprout pairs of dagger-like appendages and fence and duel in slow motion until a "hit" is scored. At that point, the "loser" is impregnated with sperm and becomes the mother, while the "father" often goes on dueling until it becomes a mother itself. However you untangle the confused gender roles, that's a whole lot of fencing flatworms for the next generation!

Male Porcupines Urinate on Females Before Sex


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What's the hardest part about porcupine sex, from the female's perspective? No, it's not being poked by the quills of a clumsy male; it's being drenched head to toe in porcupine pee as a preliminary to mating. Once a year, male porcupines cluster around available females, fighting, biting, and scratching one another for the right to mate; the winner then climbs onto a tree branch and urinates copiously on the female, which stimulates her to go into estrus. The rest is somewhat anticlimactic: the female folds back her quills so as not to impale her partner, and insemination takes only a few seconds (after which, presumably, everyone wanders off to take a bath).

Barnacles Have Enormous Penises


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You might imagine that an animal that spends its entire life tethered to one spot has a relatively sedate sex life. In fact, though, barnacles (one shouldn't say "male" barnacles since these animals are hermaphroditic) are equipped with the largest penises, relative to their size, of any creatures on earth, as much as eight times longer than their own bodies. Essentially, frisky barnacles unfurl their organs and attempt to fertilize every other barnacle in their immediate vicinity—presumably, at the same time they're being probed and prodded themselves.

Mating Snails Stab Each Other With "Love Darts"

A snail dart
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The invertebrate equivalent of Cupid's arrows, love darts—sharp, narrow projectiles made of calcium or hard proteins—are fired by some species of snails and slugs as a preliminary to the act of mating. The dart lodges in the receiving snail's skin (sometimes even penetrating its internal organs) and introduces a chemical that causes it to be more receptive to the attacking snail's sperm. (It's hard to use the pronouns "he" and "she" when referring to gastropods, since the species that employ love darts are hermaphrodites.) These love darts don't actually introduce sperm into the "female's" body; that happens the old-fashioned way, during the act of copulation.

Female Chickens Can Eject Unwanted Sperm

Rooster and hen

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Here's a fun fact about chickens that you don't often see in cartoons. Female chickens, or hens, tend to be smaller than roosters, and often can't resist when less-than-desirable males insist on mating. After the act, though, enraged and disappointed females can eject up to 80 percent of the offending male's sperm, allowing for the possibility that they might then be impregnated by roosters a bit higher up in the pecking order.

Male Honey Bees Lose Their Penises While Mating

Bees mating

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Everyone talks about colony collapse disorder—which is devastating bee populations worldwide—but not many people seem to care about the peculiar plight of the individual drone honey bee. Before a queen bee can assume her exalted title, she begins her life as a virgin bee, and must be inseminated by a male in order to step up to the throne. That's where the unfortunate drone comes in: in the course of mating with the heir apparent, the male's penis rips off, still inserted into the female, and he flies off to die. (Given the gruesome fate of male honey bees, it's no surprise that full-grown queens deliberately breed them for use in their "mating yards.")

Sheep Have a High Rate of Homosexuality

Sheep Mating

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Far from being an aberration, we now know that homosexuality—whether in humans or in other animals—is an inherited biological trait. And nowhere in the animal kingdom is homosexuality more rife than among male sheep; by some estimates, almost 10 percent of rams prefer to mate with other rams, rather than available females. And lest you think this is just the unintended result of human husbandry, studies have shown that the behavior of these sheep is reflected in a specific area of their brains, the hypothalamus, and is thus hard-wired rather than learned behavior.

Male Anglerfish Merge With Females During Mating

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Anglerfish—which lure their prey with the fleshy structures growing out of their heads—live in the deep, deep ocean, and are also relatively scarce, making for a limited supply of available females. But nature finds a way: the males of some anglerfish species are orders of magnitude smaller than the opposite sex, and literally attach themselves to, or "parasitize," their mates, feeding them a constant supply of sperm. (It's believed that this evolutionary tradeoff allows the females to grow to "normal" sizes and thus prosper in the food chain.) What happens to bite-size males who don't find receptive females? They die, sadly, and become fish food.

Male Damselflies Can Remove the Sperm of Competitors

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Most of the animals that lose out during mating season have no choice but to be content with their fate. Not so with the male damselfly, which can use its weirdly shaped insectile penis to literally scrape the sperm of its immediate predecessor out of the female's cloaca, thus increasing the odds of propagating his own DNA. One amusing byproduct of this strategy is that it takes damselflies an unusually long time to complete the act of mating, which is why these insects can often be seen flying in tandem over long distances.