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  • Thanks to massive conservation efforts and tens of millions of dollars spent over the

  • last 40 years, humans are probably the only reason giant pandas haven’t gone extinct

  • yet.

  • Of course -- as we take up more and more of its native habitat in China -- were also

  • the reason that theyre in trouble in the first place.

  • So, saving them seems like the least we could do.

  • And our efforts seem to be working, sort of -- there are about 1,600 giant pandas living

  • in the wild today and another 300 in zoos around the world.

  • But pandas present a conservation challenge like no other.

  • Giant pandas have one of the strangest and most perplexing diets in the animal kingdom,

  • and theyre equally unusual when it comes to reproduction.

  • We can help with both of these things when the animals are in captivity, but it raises

  • the question …. how do pandas manage to exist in the wild?

  • Let’s start with the food. You know that pandas eat bamboo, but did you know that it

  • makes up to 99 percent of their diet?

  • This would make total sense if pandas were a kind of herbivore, but they are in fact

  • a type of bear.

  • Instead of having complicated, fermenting four-chambered stomachs like cows, their digestive

  • systems resemble those of carnivores, with a simple stomach and short small intestine.

  • So, giant pandas actually can eat meat…. they just don’t.

  • When scientists sequenced the panda genome in 2009, they found that the bears don’t

  • even have the necessary genes for making enzymes to break down all the cellulose in bamboo.

  • As a result, giant pandas have to eat between 9 and 18 kilograms of bamboo every day.

  • It also means wild giant pandas spend as much as 16 hours a day foraging and eating, leaving

  • the rest of the day mostly for sleeping.

  • But it’s not like theyre being picky eaters. It’s likely that pandas weren’t

  • always so reliant on bamboo. But as ancient humans arrived into their territory, they

  • moved to higher elevations and started eating bamboo to avoid competing with other meat

  • eaters.

  • And it’s only now that scientists are beginning to understand how giant pandas can survive

  • on this weird, finicky diet.

  • Researchers tracked three male and three female giant pandas over the course of six years,

  • looking closely at what they ate in their natural habitat in China’s Qinling Mountains.

  • Of special interest was the amount of nitrogen, phosphorous and calcium they ate, since those

  • are the most important nutrients for mammals.

  • It turned out that pandas tweak their tastes for bamboo, from one part of the plant to

  • another, and one species to another, as the year progresses.

  • A lot of their diet consists of a certain type of bamboo called wood bamboo, and throughout

  • the year, the pandas go from eating the leaves of the plant, to the shoots, which contain

  • more phosphorus and nitrogen.

  • But as the shoots grow, they lose those nutrients -- so the pandas move to higher elevations

  • and switch to eating the shoots of another bamboo species, called arrow bamboo.

  • Then in mid-summer they switch yet again, turning their attention the leaves of the

  • arrow bamboo, which have lots of calcium.

  • By late summer, the females return to the lower elevations to give birth, at which point

  • they switch back to the leaves of the wood bamboo.

  • It’s all very complicated, and what’s worse, this poor diet also makes reproduction

  • -- which is notoriously challenging to begin with -- even harder.

  • Though pandas can reproduce when theyre as young as 4 to as old as 20, female giant

  • pandas only ovulate once a year, in the spring.

  • The window during which they can conceive is usually between one and three days. So

  • rabbits they are not.

  • Then, if a female manages to become impregnated in the spring, the embryo stays in a state

  • of arrested development known as delayed implantation.

  • Researchers think the embryo only re-starts its development after the female returns to

  • lower elevations and can eat more of the calcium-rich leaves of arrow bamboo -- nutrients she needs

  • for fetal bone growth and lactation.

  • But again, because of the bearsinconsistent and nutrient-poor diet, newborn pandas are

  • far from giant.

  • Famously described as thesize of a stick of butter,” infant pandas usually weigh

  • between 90 and 130 grams, less than a third the weight of other bear cubs.

  • So, if being cute has given them the evolutionary advantage of making us want to take care of

  • them, all I can say is, well, played pandas. Well played.

  • And on behalf of humanity, I should say sorry for making things harder for you guys.

  • But alsoyoure welcome.

  • Thank you for watching this SciShow Dose, which was brought to in large part by our

  • SciShow President of Space, Chris! Thank you Chris for your support and encouragement!

  • If you would like to be a President of Space, you can go to Patreon.com/scishow to learn

  • how you can support this channel, and get monthly rewards in the process.

Thanks to massive conservation efforts and tens of millions of dollars spent over the

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