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Have you ever looked at a snake and wondered: how does this thing drink?
看到蛇，你有没有想过：蛇是怎么喝水的？
Well, animal physiologists certainly have. And the answer isn't obvious. Snakes don't have lips like we do.
动物生理学家肯定想过。并且答案也不是显而易见的。蛇没有人类的嘴唇。
And it's pretty clear that their skinny, forked tongues weren't built for lapping up water.
显然，它们窄窄的、分叉的舌头不是用来舔水的。
And they also don't grab mouthfuls of water and tip their heads back to swallow.
它们也不会大口喝水，也不会将头向后仰去吞咽。
Back in the 1990s, researchers thought they'd figured this conundrum out. But it turns out they missed something.
回到20世纪90年代，研究人员以为他们已经解决了这个难题。但事实证明他们漏掉了一些东西。
And that something was that at least some snakes have sponge-mouths that literally soak up water.
他们忽略了，至少有一些蛇有海绵般的嘴巴，真的可以吸收水分。
Those scientists in the 90s carefully watched boa constrictors, brown tree snakes, and eastern rat snakes while they drank.
90年代的那些科学家仔细观察了大蟒蛇、褐色树蛇以及东部食鼠蛇是怎么喝水的。
And between videos and some fluid dynamics modeling, they determined that the animals were relying on suction.
通过视频和一些流体动力学模型，他们确定这些动物依赖于吸力。
Essentially, by rhythmically contracting certain muscles in their mouths and throat,
通过有节奏地收缩口腔和喉咙的某些肌肉，
they could suck water up and push it back continuously without having to tilt their heads.
它们可以在不倾斜头部的情况下将水吸上来再推回去。
And this mechanism works because the snakes can seal their mouths shut to drink, kinda like when you close your lips around a straw.
这种机制起作用是因为蛇可以闭上嘴喝水，有点像当你把嘴唇合在一根稻草上。
But then researchers observed snakes drinking without sealing their mouths.
但然后研究人员观察到了蛇不闭上嘴巴也能喝水。
Which just didn't make any sense, until they realized that their mouths were basically sponges.
这是说不通的，直到他们意识到蛇的嘴巴就是海绵。
You see, the floor and the roof of a snake's mouth are covered in soft tissues with lots of folds.
蛇嘴巴的上边和下边都覆盖着软组织，还有很多褶皱。
And, it turns out the animal can expand the space between those folds ever so slightly.
事实证明，这种动物可以轻微地扩张这些褶皱之间的空间。
The molecules coating these tissues are really good at attracting water.
包裹这些组织的分子真的很擅长吸水。
And that attraction, called adhesion, is stronger than the water's attraction to its own molecules, or cohesion.
这种吸力被称为吸附力，比水对自身分子的吸引力，或凝聚力，更强。
So, as the snake opens its mouth to allow water in, it expands these folds,
所以随着蛇张嘴让水进来，它会扩张这些褶皱，
and by a process called capillary action, water molecules can be drawn up and in against gravity.
并且通过毛细管作用，水分子可以在重力作用下被吸入吸出。
It's essentially the same as what happens with a sponge.
基本上就和海绵一样。
If you put a squeezed one on a wet spot and then slowly release, the water will travel up and in.
如果你把一个挤压过的海绵放在潮湿的地方，然后慢慢放手，水会在海绵中穿行。
And once the animal's skin-sponge is nice and wet, further movement of the bones and muscles in the jaw and head will compress the mouth.
一旦这种动物海绵般的皮肤变湿，其颚部和头部骨骼和肌肉的进一步运动就会挤压嘴巴。
This squeezes the water out from the folds so it can be swallowed.
这将水从褶皱中挤出来，这样水就可以被吞下去了。
Now, this sponge-like drinking likely occurs alongside the more active suction-drinking, rather than instead of it.
这种海绵式的喝水方式很可能与更加活跃的吸入喝水方式同时发生，而非代替它。
And it seems to be totally unique to snakes, even though some lizards have similar folds of mouth tissues.
这种方式似乎是蛇特有的，即便一些蜥蜴的嘴部组织中也有类似的褶皱。
That tells us that they probably didn't evolve these folds for drinking.
这告诉我们，蜥蜴可能没有为了饮水而进化这些褶皱。
More likely, they're what biologists call an exaptation: a trait that evolved for one purpose, but now serves another.
更有可能的是，它们是生物学家所说的变异：一种为一个目的进化而来的特征，现在又为另一个目的服务。
Scientists think they exist because snakes swallow their prey whole.
科学家认为它们之所以存在是因为蛇会将猎物整个吞下。
To do that, their jaws need to open incredibly wide and wrap around their meal, hence, expandable skin.
为此，它们的下颚需要张开到非常大，以包裹住它们的食物，因此，需要可扩张的皮肤。
So these folds probably evolved for eating, and they just happened to be pretty useful for drinking, too.
所以这些褶皱可能为了进食而进化，并且它们恰好也很适用于饮水。
And there's probably more to this story. The truth is, scientists are still not completely sure how snakes drink.
这个故事可能还有更多内容。事实是，科学家仍不能完全确定蛇怎么喝水的。
Some species seem to use both these methods, others favor one, and some might switch things up as they get older and grow bigger.
一些动物似乎同时使用这两种方法，另一些则偏爱其中一种，还有一些可能会随着年龄的增长和体型的增大而改变。
So it turns out that snake drinking is still a bit of a puzzle!
所以事实证明蛇饮水是个谜！
But what we do know is cool and weird, and just, I mean, sponge-mouths. That just doesn't even seem real!
但我们所知道的也是很酷很奇怪的，我说的是海绵一样的嘴巴。这似乎都不真实！
Thank you for watching this episode of SciShow.
感谢收看本期节目。
And if you want more jaw-dropping snake facts, be sure to check out our episode on 6 extraordinary serpents.
如果你想知道更多关于蛇的惊人事实，一定要起看看我们的六种特别的巨蛇。
And, if you just want a little more science in your life in general, go ahead and click that subscribe button.
如果你想了解更多生活中的科学知识，请点击订阅按钮。
Or, you can check out our other channels, SciShow Space and SciShow Psych!
或许你可以看看我们的其他频道——《SciShow Space》和《SciShow Psych》！
