Biology’s Ten Worst Love Stories

Animal sex can get pretty weird

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Animal sex can get pretty weird. And we're not comfortable with some of its variants. I'm sure I'm on someone's watch list after researching this post; while searching for juicy examples, I kept coming across sites barred by the Smithsonian's internet filter—such as the Wikipedia entry on "sexual cannibalism." But scientists find it fascinating. A National Zoo great cats curator recently told my colleague Megan Gambino: "I think animal mating, while it’s very funny, is just a really interesting topic to talk about and one that people often shy away from because, oh, it’s taboo. But it’s pretty vital. It’s the very crux of existence."

And so, in honor of today, here's my top ten list of the worst—and weirdest—love stories from the world of biology:

10. Giant pandas: They are solitary creatures, and female pandas ovulate for only two or three days a year, so hooking up might be a bit of a problem in the wild. Even in captivity, panda mating isn't always successful, leading zoo keepers to try everything from behavioral training to panda porn. The National Zoo's current couple, Tian Tian and Mei Xiang, were unsuccessful in their mating attempts yet again this year; zoo curators then artificially inseminated Mei Xiang—which is how we got Tai Shan in 2005.

9. Pseudobiceros hancockanus: These orange-and-purple marine flatworms are hermaphroditic, meaning they can act as either a female or a male. How do they sort it out? Through penis fencing (see here for video). They battle each other with their penises and the winner pierces the other to deliver its sperm. The loser has to spend a lot of its energy and resources caring for the developing eggs.

8. Short-beaked echidnas: These spiky Tasmanian animals hibernate in winter, but that doesn't deter some males from sex. They'll happily mate with hibernating females; sometimes the females wake up, only to go back into hibernation, while others just sleep right through it. Scientists think that by re-entering hibernation, which would delay the development of a fetus, the female gets a chance to mate with a better quality male and abandon her first pregnancy.

7. Porcupines: The weird thing about porcupine sex has nothing to do with the quills. Male North American porcupines that want to mate with a female will first perform an elaborate dance, and then if she's receptive, the female will let him douse her with urine. Ew!

6. Muscovy ducks: Males have a ballistic, corkscrew-shaped penis that they can use to force themselves onto unwilling females. Females, though, can fight back, at least against unwanted pregnancy, by refusing to relax her corkscrew-shaped genital tract. As a result, although a third of matings are forced, only three percent of offspring are born from those matings.

5. Redback spiders: When mating, the male redback spider performs a somersault that places his abdomen right above the female's mouth, thus setting himself up to be eaten when copulation is done. It's a noble sacrifice in the name of his genes—cannibalized males copulate longer and fertilize more eggs than males that survive mating, and females are more likely to reject other males after they've eaten their first mate.

4. Praying mantises: Like the redback spider, the female praying mantis often eats her mate. But she doesn't always wait until they're finished to start her meal. Sometimes the female will bite off the male's head while they are copulating.

3. Bean weevils: The male bean weevil's penis is covered with long, sharp spikes that can inflict serious scarring on a female. To make matters worse (for the female, that is), the longer the spines, the more successful the male is at depositing his sperm and fathering her young.

2. Banana slugs: Like the marine flatworms, banana slugs are hermaphrodites. When they copulate, each slug inserts its penis into the other. When they're done, though, one slug may chew the penis off the other, and sometimes you end up with two penis-less slugs. Scientists call it apophallation.

1. Harpactea sadistica: This spider from Israel performs something called "traumatic insemination," which is also characteristic of several insect species. The male injects sperm into the female by piercing her abdomen with his penis. This can leave an open wound prone to infection. Bedbugs, which also practice this method of copulation, at least provide the female with a spermalege that helps to repair the damage.

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