Why are blue whales so enormous? - Asha de Vos

蓝鲸为什么如此巨大？——阿莎·德沃斯

Transcriber: Andrea McDonough Reviewer: Bedirhan Cinar

翻译人员: Yinglei Li 校对人员: Ying Wang (王莹)

在地球上出现过的动物中，

Blue whales are the largest animals that have ever roamed the planet.

蓝鲸是最大的。

They’re at least two times as big as the biggest dinosaurs—

它们的体积至少是最大恐龙的两倍

“好大啊！”

“that’s big!“—

the length of a basketball court,

蓝鲸的身长与篮球场相当，

and as heavy as 40 African elephants.

体重等于40头非洲象的总和。

If that’s not enough to make you marvel, here’s something that will.

如果这些数据还不足以震撼你，

那请接着看下去。

They’ve grown to this enormous size

蓝鲸能长到这么大

by feeding exclusively on tiny shrimp-like creatures called krill—

仅仅靠吃一种叫鳞虾的小生物。

that are no bigger than your little finger.

它们比你的小拇指还小。

In many ways, the sheer size of krill

磷虾的微型身材

seems to have driven the evolution of the blue whale.

似乎在很多方面都促进了蓝鲸进化。

See, krill are so small but are found in dense patches.

看，虽然它们体积小，

但出现的一群群磷虾总是数量众多。

For increased efficiency,

为了提高效率，

blue whales have evolved to use a feeding strategy called lunge feeding.

蓝鲸进化出

一种

称为 ”突进捕食法" 的进食方式。

Basically, the whale accelerates towards a prey patch

简单来说，蓝鲸一方面会加速游向虾群，

and opens its mouth wide.

另一方面会把最张得更开。

为提高进食能力，蓝鲸的嘴张得很大。

To increase the capacity, its mouth expands.

The special, accordion-like blubber layer

从嘴部一直延伸到腹部底下的

that extends from its snout to its belly button

特殊褶皱状鲸脂层，

enables the whale to engulf large quantities of prey-laden water.

使鲸鱼能够吞食大量

含有食物的海水。

With each giant gulp,

每一大口中，

the whale takes in 125% of its body weight in water and krill.

含有的海水和磷虾分量

是鲸鱼体重的1.25倍。

The whale must then expel the water while retaining the yummy krill.

之后鲸鱼要排出海水，

并保留美味的磷虾。

To do this, it uses its baleen,

这一步骤要用到鲸须，

the comb-like structure made of the same stuff our nails and hair are made of,

鲸须形似梳子

质地和鲸的舌头

and its tongue.

以及我们的指甲、头发是一样的。

It’s pretty crazy that the blue whale’s heart is as big as a small car,

蓝鲸的心脏和小轿车一样大

太不可思议了。

a child could crawl through its arteries,

小孩可以爬过它的动脉，

its tongue weighs as much as an elephant,

蓝鲸的舌头和大象一样重，

but its esophagus is so small,

但它的食道太窄，

the whale could choke on a loaf of bread.

一块面包都能噎着它。

These whales are really not designed to feed on anything larger than krill.

蓝鲸的身体结构

使得它们只能吃磷虾这样小的食物。

It’s estimated that blue whales eat four tons of krill per day.

据估计，蓝鲸每天要吃4吨磷虾。

Because of their incredible design,

依靠这惊人的身体结构，

蓝鲸每次潜水进食获得的能量

each dive provides the blue whale with 90 times as much energy as is used.

是这一动作消耗掉的90倍。

Every mouthful of krill provides almost 480,000 calories,

一大口磷虾能提供48万卡热量，

the same amount you get from eating 1,900 hamburgers.

你要吃1900个汉堡包 才能获得这么多热量。

But, why are blue whales so big?

那么，为什么蓝鲸这么大呢？

Blue whales are considerably larger than the largest living land animal,

蓝鲸比陆地上最大的动物——大象

要大得多。

the elephant.

The heavier an animal is,

动物越重，

the greater its relative surface area.

它的相对表面积越大。

As weight increases,

当体重增长到一定程度

there’s a point at which the legs of that animal would simply collapse.

动物的腿将因支撑不住体重

而瘫倒。

That explains why elephants don’t stand on the delicate legs of a horse.

这就是为什么大象的腿

不像马的腿那么细。

They need legs shaped like stout pedestals

它们需要结实的腿脚

to hold their bodies up against gravity.

抵抗地球引力，撑起身体。

In water, the situation is quite different.

但在海水里，情况就不同了

Buoyancy counteracts the gravitational pull on the body

浮力抵消了往下拉身体的引力

and their great bulk is therefore partially supported by the water.

因此海水对支撑蓝鲸的大身材

起到一定作用。

So, the ocean is a great place for species that want to grow bigger.

看来海洋是

大体积物种的天堂。

The other secret to their size is their diet.

蓝鲸这么大的另一原因在于它们的饮食结构。

By evolving such a huge mouth,

蓝鲸进化出巨大的嘴

the whale’s have specialized to catch enormous quantities

这样它们就能捕食大量

of highly abundant and nutritious prey,

供应充足且营养丰富的食物

which provides the energy needed to grow so big.

获取的能量使它们能够长这么大。

But, now maybe you’re wondering why blue whales aren’t any bigger?

现在，也许你在疑惑

为什么蓝鲸不长得更大？

After all, the ocean sounds like nirvana for any growing beast.

海洋不就像是

庞然大物的天堂吗?

Well, while lunge feeding may have allowed blue whales

原因在于，尽管蓝鲸靠突进捕食法

能够快速吃到大量食物，

to become the biggest animal to have ever roamed the planet,

成为了地球上存在过的

最大的动物

by enabling them to feed efficiently in dense prey patches,

但这种捕食法也需要消耗能量。

it isn't cost free.

Scientists compared all the costs involved with lunge feeding

科学家将突进捕食法的所有消耗

to the energy gained from the krill they eat.

与从磷虾身上获得的能量做了比较。

What they found is that when the whale’s body increases in size,

结论是，随着蓝鲸的体积增大，

the energy that body demands rises faster

身体消耗的能量快速增加，

而食物提供的能量却增加得要慢一些。

than the extra energy they get from their food.

Feeding whales needs 15 times the energy required to remain still

进食需要的能量是静止不动时的15倍

and 5 times more energy than used when swimming.

游泳时的5倍。

Calculations show that the largest a lunge feeder can grow is 33 meters,

经计算，

使用突进捕食法的动物 最多能长到33米，

pretty much blue whale size.

蓝鲸差不多就是这么大。

蓝鲸应该多多感谢磷虾，

Turns out blue whales have a lot to thank krill for:

neat, evolutionary adaptations that would not have been possible

如果磷虾长得再大一些，

蓝鲸就无法顺利进化， 也无法适应生存环境。

if krill were not so small.

It’s incredible that these tiny creatures have allowed blue whales

这些小生物

竟然能让蓝鲸的体积 达到地球上动物的极限，

to really push the limits of size on our planet.

着实令人惊叹。

Makes you wonder if that old adage, “you are what you eat,”

也让人怀疑那句古话

“吃什么就是什么”

really does apply in blue whale world.

似乎不适用在蓝鲸身上。