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Why Is it so Hard for Pandas to Get Pregnant?

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In the wild, giant panda mating occurs just as nature specials would have you believe. There’s intense competition for each female, and the dominant male will mate with her several times to ensure success. And that strategy works: Wild female pandas generally give birth every two years. But that low birth rate means that captive breeding programs are essential to sustaining the endangered species. And in captivity, mating and successful pregnancies are tricky affairs—which is why it’s always a big deal when a cub is born, and devastating when one dies, as the 6-day-old cub at the National Zoo did last week.

Breeding pandas in captivity requires cooperation from zoos across the world, and is difficult for a number of reasons. Early on, scientists realized that the bears either lost interest in mating naturally or seemed like they didn’t know how. Take, for example, Ling-Ling and Hsing-Hsing, which were given to the National Zoo to commemorate Nixon’s 1972 visit to China. They tried to mate, unsuccessfully, for a decade; once they figured out what they were doing, they had five cubs, but none reached adulthood.

Scientists speculate that the awkward fumbling that sometimes occurs between captive pandas might be because the cubs were taken from their mothers too early and have never seen the deed done; lack of interest in mating might be attributed to lack of competition for the female.

Even if pandas are in the mood, time is working against them. A female is in heat only once a year, in the spring, for 12 to 25 days—but she’s only receptive to mating for two to seven of those days, and she’s only actually fertile for 24 to 36 hours. After that time passes, any more attempts at mating have to wait until the next year. So when scientists aren’t experimenting with other methods to get pandas to go at it—like dosing one male with Viagra or showing a matched pair panda porn—they often rely on artificial insemination to get the job done.

After Mating: The Waiting Game

Neither artificial insemination nor old-fashioned mating will guarantee a pregnancy, and zoologists must bide their time before they know for sure that a panda is expecting. This, too, is complicated. Like many other species, pandas experience embryonic diapause, in which the embryo is fertilized, but not yet implanted in the uterine wall. The offspring can’t continue to grow until it has implanted, so while the gestation period is around 50 days, some panda pregnancies can stretch out to more than 160 days because of diapause.

And as if that all wasn’t difficult enough for zookeepers to figure out, female pandas can experience pseudopregnancy—they aren’t actually pregnant, but exhibit the same behaviors as pregnant pandas (decreased appetite, sluggishness, and even similar changes in hormones). It's almost impossible to distinguish between the two, because recently implanted fetuses are often too tiny to be spotted on an ultrasound. But there are some developments that might help scientists determine whether or not a panda is actually pregnant: Scientists in the reproductive physiology department at the San Diego Zoo used thermal imaging cameras to help determine if their panda, Bai Yun, was pregnant (she was—watch her cuddling with the little guy on the zoo's Panda Cam); the idea is that right before a fetus attaches to the uterus, there is increased blood flow to that area, which will show up as bright red on the camera.

Still, even if a panda is pregnant, and her cub is born, the tiny, blind and toothless young, which is about the size of a stick of butter at birth (or 1/900th the size of its mother), might not survive.

It all adds up to grim odds for pandas: In 2004, there were approximately 1600 left in the wild, and zoos around the world currently hold around 300 of the animals. But despite the rocky start that captive breeding programs had and the ongoing challenges zoos still face, the program has had its successes, especially in the last few years. And as scientists learn more about how these bears mate and raise their young, more pandas will have cubs that live to adulthood.

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Big Questions
What Are Curlers Yelling About?
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WANG ZHAO/AFP/Getty Images

Curling is a sport that prides itself on civility—in fact, one of its key tenets is known as the “Spirit of Curling,” a term that illustrates the respect that the athletes have for both their own teammates and their opponents. But if you’re one of the millions of people who get absorbed by the sport once every four years, you probably noticed one quirk that is decidedly uncivilized: the yelling.

Watch any curling match and you’ll hear skips—or captains—on both sides barking and shouting as the 42-pound stone rumbles down the ice. This isn’t trash talk; it’s strategy. And, of course, curlers have their own jargon, so while their screams won’t make a whole lot of sense to the uninitiated, they could decide whether or not a team will have a spot on the podium once these Olympics are over.

For instance, when you hear a skip shouting “Whoa!” it means he or she needs their teammates to stop sweeping. Shouting “Hard!” means the others need to start sweeping faster. If that’s still not getting the job done, yelling “Hurry hard!” will likely drive the point home: pick up the intensity and sweep with downward pressure. A "Clean!" yell means put a brush on the ice but apply no pressure. This will clear the ice so the stone can glide more easily.

There's no regulation for the shouts, though—curler Erika Brown says she shouts “Right off!” and “Whoa!” to get her teammates to stop sweeping. And when it's time for the team to start sweeping, you might hear "Yes!" or "Sweep!" or "Get on it!" The actual terminology isn't as important as how the phrase is shouted. Curling is a sport predicated on feel, and it’s often the volume and urgency in the skip’s voice (and what shade of red they’re turning) that’s the most important aspect of the shouting.

If you need any more reason to make curling your favorite winter sport, once all that yelling is over and a winner is declared, it's not uncommon for both teams to go out for a round of drinks afterwards (with the winners picking up the tab, obviously). Find out how you can pick up a brush and learn the ins and outs of curling with our beginner's guide.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Why You Should Never Take Your Shoes Off On an Airplane
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What should be worn during takeoff?

Tony Luna:

If you are a frequent flyer, you may often notice that some passengers like to kick off their shoes the moment they've settled down into their seats.

As an ex-flight attendant, I'm here to tell you that it is a dangerous thing to do. Why?

Besides stinking up the whole cabin, footwear is essential during an airplane emergency, even though it is not part of the flight safety information.

During an emergency, all sorts of debris and unpleasant ground surfaces will block your way toward the exit, as well as outside the aircraft. If your feet aren't properly covered, you'll have a hard time making your way to safety.

Imagine destroying your bare feet as you run down the aisle covered with broken glass, fires, and metal shards. Kind of like John McClane in Die Hard, but worse. Ouch!

Bruce Willis stars in 'Die Hard' (1988)
20th Century Fox Home Entertainment

A mere couple of seconds delay during an emergency evacuation can be a matter of life and death, especially in an enclosed environment. Not to mention the entire aircraft will likely be engulfed in panic and chaos.

So, the next time you go on a plane trip, please keep your shoes on during takeoff, even if it is uncomfortable.

You can slip on a pair of bathroom slippers if you really need to let your toes breathe. They're pretty useless in a real emergency evacuation, but at least they're better than going barefoot.

This post originally appeared on Quora. Click here to view.

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