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Sorry, guys! Do you ever have those days when you just don't have the energy to do all that much?
对不起，小伙伴们！你们曾经有过做什么都没力气的时候吗？
And when you do move, you move really slowly?
当你动时，却动得很慢？
Well, that's pretty much what every day is like for a sloth.
好吧，这种状况和树懒的日常活动很类似。
Sloths are the slowest mammals on Earth.
树懒是地球上行动最慢的哺乳动物。
Just how slow are they? Well, it can take a sloth up to an entire month to travel a single mile on the ground.
到底有多慢呢？树懒花费整整一个月的时间，才在地面上挪动一英里。
But that's OK, because sloths spend most of their lives in trees,
但是，没关系，因为树懒一生中的大部分时间都花在树上，
where they can move just a little bit faster.
在树上，它们可以移得快些儿。
Their powerful arms and curved claws let them move easily from branch to branch
它们强有力的上臂和带钩的爪子能让它们在美洲中部和南部的雨林
in the rain forests of Central and South America, where they're from.
树枝间自由移动，它们来自那里。
Sloths are identified by the number of these claws that they have on their front feet.
树懒是以它们前足上爪子的数目来分类的。
There are two-toed sloths and three-toed sloths.
它们分为二趾树懒和三趾树懒。
But good luck actually spotting a sloth swinging through the trees—
幸运的话，我们可以看到树懒在树间荡秋千。
these guys spend very little time moving, and a whole lot of time sleeping and eating.
但是这些家伙很少花时间运动，大量的时间都用来睡觉和吃东西。
Sounds sort of boring, doesn't it? Wrong!
听起来有点儿无聊，不是吗？你错了！
If you ask me, sloths are super cool.
如果你问我的意见，我会觉得树懒非常聪明。
They're not lazy—they're just really good at conserving, or saving, their energy.
它们并不是懒，只是非常懂得保存或者说节省能量。
Their diet of leaves and bark doesn't provide them with a whole lot of nutrition,
它们吃得树叶和树皮不能为它们提供很多能量，
so they need to save as much energy as they can.
因此它们需要尽其所能地节省能量。
One way sloths manage to conserve their energy is by keeping their food in their bodies for as long as possible.
树懒设法储存能量的方法之一就是让食物在体内停留尽可能长的时间。
Sloths have big stomachs that can hold a large amount of food.
树懒们的胃很大，可以储存大量的食物。
While it might take you or I just a few hours to digest our breakfast,
也许你我只需要花几个小时就能消化早餐，
it can take a sloth 30 days to digest a single leaf.
但树懒却可以花30天的时间来消化一片树叶。
Since they digest their food so slowly, sloths don't get a lot of energy very quickly from their food,
因为它们消化食物的速度太慢了，所以不能通过食物快速地获得大量的能量，
but they also don't use a lot of energy to break it down.
但同时它们也不需要消耗大量的能量去分解食物。
Plus, because their stomachs work so slowly, they don't need to go to the bathroom as often as we do.
此外，因为它们的胃工作得很慢，它们也不需要像我们一样经常上厕所。
In fact, one of the few times that three-toed sloths come down from the trees is for their weekly potty break.
事实上，三趾树懒每周也偶有几次从树上下来稍作休息。
Once a week! That's it!
一个星期一次！是的！
Another weird way sloths conserve energy is by having a naturally low body temperature.
它们保存能量的另一种特殊方法是低体温。
If our body temperature changes more than three degrees, it probably means that we're sick.
如果人类的体温上下波动超过三度，那可能意味着我们生病了。
But that's not so for the two-toed sloth.
但对于二趾树懒来说不是这样。
It has the lowest body temperature of any mammal in the world—it can dip as low as 30 degrees Celsius.
它是世界上所有哺乳动物中体温最低的，可以低到30摄氏度。
Most mammals, including us, have body temperatures of 36 degrees Celsius or higher.
大多数哺乳动物，包括人类，体温都是36摄氏度甚至更高。
After all, it takes a lot of energy to keep your body warm.
毕竟，保持体温需要消耗大量能量。
So when sloths aren't active, most of time,
所以，大部分时候，树懒不动时，
their bodies just automatically switch into low-energy mode, and their body temperature drops.
它们的身体会自动调到低能耗模式，体温也会随之下降。
The last weird way that sloths save energy is my personal favorite.
树赖最后一个节省体能的奇怪方法是我自己最喜欢的。
Three-toed sloths are the only mammal that can rotate their heads almost all the way around their bodies, like owls do.
三趾树赖像猫头鹰那样，是唯一一种可以几乎全方位旋转头部的哺乳动物。
This is because they have more vertebrae, or bones in their neck, than other mammals do.
这是因为它们和其他哺乳动物相比，有更多的脊椎骨或者颈骨。
This cool trick helps them look for food and keep an eye out for predators without having to go anywhere or do anything.
这种很酷的技巧能帮助它们寻找食物，时刻小心捕食者的行动，而不用去任何地方或做点什么。
They can just hang out, and twist their heads around, observing the world around them.
它们只需要躲起来，转动它们的头，观察周围的世界。
So sure, sloths are slow—but not because they're lazy.
所以可以肯定，树赖行动缓慢不是因为懒。
They've just adapted to a nice, mellow, low-energy lifestyle that works out well for them.
它们只是适应了一种成熟低耗能的良好生活方式，这对它们来说很有用。
They're basically the ultimate energy-saving machine!
它们基本上可以称作终极节能机器！
Thanks for joining us on SciShow Kids! I'm Jessi, this is Squeaks, and we'll see you next time.
感谢收看儿童科学秀！我是杰西，这是Squeaks，我们下次再见！
