Quora：北极熊的毛怎么会变绿呢？--艾略特·霍奇斯的回答

Polar bears have fur that looks white...

北极熊的毛一般都是这样的白色。

...except for when when their fur turns green like this...

不过有时它们的毛会变成绿色，就像这样。

Why does their hair turn green, you ask? Well, that is because a polar bear's hair is

translucent and hollow like a straw. (Human hair is more like a cable and does not

present a cavity.)

Underneath a microscope, a polar bear's hair looks like this:

你要问了，为什么会这样呢？原因就是北极熊的毛发是半透明的，而且像稻草一样是空心的。（人的毛发更像一根缆绳，内部没有空腔）

北极熊的毛在显微镜下看就像这样：

And algae, particularly in warmer, muggier climates, can start to grow not just on the

hair but inside its cavity as well, effectively tinting our once white polar bear green.

而藻类植物不但能在北极熊的毛发表面生长，还能进入毛发内部的空腔，把一头白熊染成绿熊（这种情况在温暖潮湿的气候下尤为显著）

As Esther Inglis-Arkell makes clear here:

就如同Esther Inglis-Arkell在《北极熊毛发的神奇之处/诡异真相》节目中所说：

This is actually pretty common among zoo bears, especially in hot and muggy climates.

It's not just that algae grows on their hair. It's that algae grows inside their hair. While

most animals produce hair that's a long, thin cable, polar bears produce hair that's a

hollow tube - like the world's most dangerous drinking straw. The tube is colorless,

but it's made with translucent material. Any light that comes in is scattered, and so it

appears white. (This is one of the reasons polar bears look brightest in direct sunlight.)

In cold or harsh climates, the tube of hair stays empty. In hotter ones, even if the bear

is being regularly washed, algae starts growing inside the tube of hair, turning large

sections of the bear green. (The Biggest Myth About Polar Bear Fur (And the Weirdest

Truth)

其实这种现象在动物园里的熊身上非常普遍，在炎热潮湿的气候下更是如此。藻类不仅仅只长在它们毛发表面，还长入了它们的毛发腔内。其余的大多数动物毛发就像一根又细又长的缆绳，但北极熊的毛就像一根中空的管子——它可被称作世界上危险性最大的吸管。这根管子是无色的，但它是由半透明物质组成的。所有进入管腔的光线都被散射开来，使北极熊的毛呈白色（这也是为什么北极熊在阳光直射下会异常的亮）。在冰冷严酷的气候环境下，毛管腔一直是空心的，但一旦气温转暖，藻类植物就会开始在管腔内生长，把熊身上大半的毛发染成绿色，就算给它定时清洗也避免不了。

Tragically, once green, polar bears have lost their lucrative Coca-Cola sponsorships. Luckily they are known to have found gainful employment elsewhere:

可惜的是，北极熊变绿之后就失去了可口可乐公司的丰厚赞助金（译者注：北极熊经常被拿来做可口可乐广告里的角色），不过绿熊们还是能有幸从其他地方拿到工作机会的：