生命的进化（1979）

The moth has either jammed the bat's signals
要么发出另外一些警告蝙蝠的声音想使它离开
or sent some kind of warning which puts the bat off.
不管怎样，飞蛾几乎逃走了
Anyway, the moth nearly always escapes.
我们可以假设这种打架的方式将会继续进化
We may assume the battle of techniques will continue to evolve
蝙蝠进一步发展它的声纳功能
as bats further develop their sonar equipment.
而且总是蝙蝠的能力占优势
The apparatus often dominates the faces of bats.
巨大的耳朵来接收回声
Huge ears for detecting the echoes,
在鼻子上，边缘有矛一样的东西来侦察回声
and on the nose, leaves, flanges and spears for directing the sound,
因此，它们看上去就像 中世纪空想出来的怪兽一样
so they look as grotesque as any gargoyle produced by the medieval imagination.
有些蝙蝠吃那些比蚊子和草蜻蛉稍大的昆虫
Some bats tackle insects much bigger than mosquitoes or lacewings.
这一只准备落在森林地上
This one is quite prepared to alight on the forest floor
和一只巨型蟑螂进行格斗
and grapple with a giant cockroach.
昆虫的牙齿是从树鼠那儿继承来的， 像它的祖先的一样
The insect-eating teeth, inherited from the shrew-like ancestor,
首先撕裂了昆虫坚韧的角质膜
are essential here to break up the tough chitin of the insect's body.
当它们倒挂着的时候翅膀像某一种帐篷
When it hangs up, the wings form a kind of tent,
防止猎物的逃脱 这是最好的方法
preventing bits of the prey from dropping out. This is a top view.
甚至对于蝙蝠来说一个强劲的对手，蝎子
And an even tougher adversary for the pallid bat, a scorpion.
要小心避免被毒针♥刺♥到
The poisonous sting is to be carefully avoided.
有些蝙蝠是真正的食肉动物
And some bats are real carnivores.
这种巨大的丝绵树容纳着一个小的蝙蝠群体
This huge silk cotton tree contains a small colony of them.
它们挂在高处的空心处
They are hanging at the very top of the hollow interior,
和其它种类的蝙蝠共享着这棵树
sharing the tree with other species of bats.
这是很奇怪的，因为它们是以其它的蝙蝠为食的
This is strange, because this carnivorous species feeds on other bats,
但是在这，它与邻居们和平相处
but here it leaves its neighbours in peace.
它们同样把鸟作为食物， 那些是晚上在鸟的栖息地抓到的
The also feed on birds, which they catch on their roosts at night.
这是假吸血鬼蝙蝠，但它不吸血
This is Vampyrum spectrum, but it doesn't actually suck blood.
这不是真正吸血鬼
This is not the true vampire.
这是。它的牙齿和嘴型非常适合吸血
This is. Its teeth and mouth are very specialised for feeding on blood.
吸血蝙蝠最早以食草动物旁边的 成群昆虫为食
Vampires may have originally fed on insects that cluster around grazing animals
在地上追捕它们
and chased them on or near the ground.
用剃刀似的牙齿把毛皮刮开
By shaving away the skin with razor teeth
然后用唾液防止渗出的血液凝固
and having a saliva that prevents oozing blood clotting,
吸血蝙蝠展示了哺乳动物可以变得如何极端
the vampire shows how extremely specialised a mammal can become.
可能全部始于昆虫
And it probably all started with insects.
最原始的食虫蝙蝠
And the originally insect-eating bat
在亚利桑那州和墨西哥 吃昆虫的蝙蝠向着另一个方向进化
evolved in yet another direction in Arizona and Mexico.
大型植物，像仙人掌、丝兰、龙舌兰
This is the land of big plants, like cactus, yuccas and agaves.
龙舌兰花从约六米高的茎干发出
The agave flowers, branching from a mast some six metres high,
吸引以花蜜为食的蜂鸟
attract hummingbirds that feed on the nectar.
和其它昆虫
And insects, too.
可能这里是最先吸引蝙蝠的地方
It was probably these that attracted bats in the first place.
然后才吃花蜜的
Nectar feeding came later.
一小部分蝙蝠从这棵树移到那棵树
The bats, in small parties, move from plant to plant,
吮吸着丰富的花蜜
dipping and sipping at the energy-rich nectar.
它们经常还带走花粉
Often they get covered in pollen.
它们来往于不同的植物之间 并使异花授精
In this way they ferry it from plant to plant, so bringing about cross-fertilisation.
因此，蝙蝠和植物都在不停地进化， 而且变成不相像的伙伴
So both bat and plant have evolved together to become unlikely partners.
其它蝙蝠，为了适应自然
As in other bats, this feeding specialisation involves adaptation.
长鼻子和舌头可以帮助它们 进入花的内部很深
Long noses and long tongues enable them to reach deep into the flowers.
当它们飞行的时候，看看这些慢动作
When flying, seen here in slow motion,
它们发出微弱的声纳，因此被叫作低音蝙蝠
they emit a weak sonar, so they've been called whispering bats.
（快而不规则的脉冲）
(FAST IRREGULAR PULSE)
带着花粉而且滴下花蜜
Carrying pollen and dripping nectar,
蝙蝠飞向另一棵龙舌兰，这时， 异花授粉就会发生
this bat will fly on to another agave, where cross-fertilisation will occur.
当蝙蝠帮助做这些时，树就会结果
When the bat has helped that to happen, the fruit will appear.
当然，果实也成为蝙蝠食物的一部分
And fruit, too, has become a food for bats.
这个把舌头搭在香蕉上
This one, lapping at a banana with its tongue,
以及用牙齿与螳螂打架的是同一类
was the same kind as the one biting into a cockroach with its teeth.
有些蝙蝠有更宽广的味觉
For some bats have developed broad tastes.
然而，有些蝙蝠是完全的以水果为食
Some, however, are exclusively fruit-eaters,
包括一些很大型的
and they include the biggest of all.
这些几乎不住在洞穴里
These hardly ever live in caves,
而是倒挂在树上，叫露营
but instead hang themselves up in great roosts in trees, called camps.
它们的翅膀非常宽大，可以达到两米
Their wings are immense, up to two metres across.
像鸟一样，它们要修饰羽毛， 以保证更好地飞行
Just as birds have to groom their feathers with great care to keep themselves airworthy,
因此，蝙蝠要花大量的时间， 小心翼翼地清理它的皮肤
so bats spend a lot of time meticulously cleaning the elastic membrane of skin
它们依靠的皮肤
on which they depend.
狐蝠被称作会飞的狐狸，实际上， 它们比看起来更狡猾
Fruit bats are often called flying foxes, and indeed their faces do look rather foxy.
它们有很大的眼睛
The fact that they have large eyes
非常明显的是它们没有大耳朵， 鼻子上也没有奇形怪状的装饰
and no immense ears or grotesque ornaments on their noses is significant.
它们没有声纳，而是依靠视觉认路
They have no sonar and rely instead on vision to find their way around.
实际上，它们和以昆虫为食的蝙蝠有很大的区别
In fact they are so different from insect-eating bats
它们遗传自哺乳动物的另一分支
that they may well be descended from a different branch of the primitive mammals.
它们是很好的飞行者， 并且时常进行50公里的飞行
They're powerful flyers and regularly go off on journeys of 50km
仅仅是为了一棵结满果实的树
just to find a tree in fruit.
然而有些有些的速度很慢
These are in slow motion.
蝙蝠翅膀的构造和鸟的有着很大的区别
The structure of a bat's wing is very different from that of a bird's.
非常有用的是，鸟的羽毛的边缘只有一根指头
The bird's, in effect, is formed from just one finger fringed with feathers.
其它的指头完全部消失了
All the other fingers have been effectively lost.
但是蝙蝠的祖先没有又长又硬的羽毛
But the bat's ancestors didn't have feathers with long stiff quills.
它们用另一种方式长出了宽宽的羽毛
They created a broad wing by a different method.
保留了所有的手指，并且变得更长了
By retaining all their fingers and greatly elongating them
以此来支撑它们的翅膀
to support the wing membrane.
它们的脚也帮助隔膜到达脚踝
Their feet also help, for the membrane goes right down to the ankle.
只有大拇指是闲着的
Only the thumb remains free,
蝙蝠用它进行梳洗
and that the bat needs for its toilet
并在它们攀上树枝时抓住树枝
and to hook onto branches as it clambers about.
早在五千万年前，当第一个哺乳动物飞翔时
When, over 50 million years ago, the first mammals flew,
它们就为子孙们开♥发♥了一个大的可能性
they opened up great possibilities for their descendants.
实质上，它们拥有夜晚的天空
They had the night sky virtually to themselves,
它们发展成不同的种类去充分利用这一点
and they developed into a multitude of different forms to take full advantage of it.
直到今天，它们几乎有一千多种不同的种类
Today there are nearly 1,000 different species of them,
飞行在天空中
flying through the skies of the world.
很多仍然是昆虫为食， 就像它们远古的祖先一样
Many of them have remained insect-feeders, like their earth-bound ancestors,
但是水果、花蜜、血、鸟类甚至其它的蝙蝠
but fruit, nectar, blood, birds and even other bats
决不完全是它们能找到的食物
is by no means the complete list of the diets they've discovered for themselves.
有一种已经变成了很好的捕鱼者
And one of them has actually become a fisherman.
它生活在美国中部
It lives in Central America.
它和以昆虫为食的蝙蝠有很近的关系， 像这种也吃甲虫
Its closest relatives are all insect-feeders, and it too will take a beetle, like this one,
用特殊的方法
though in a unique way.
它把后腿当做抓钩来抓甲虫
It caught that beetle by using its hind legs as grapnels,
也用同样的办法抓鱼，看！
and it goes after fish in the same way. Watch.
它抓住了鱼，但是还不够
It hooked the fish, but not well enough.
因此它回来了
So back it comes.
像其他的蝙蝠一样，它立即把猎物送进嘴里
Like other bats, it immediately transfers its capture into its mouth.
只有回到它的栖息地， 它才吃东西，并填满它的胃
And only eats it when it gets back to its roost, stuffing some of it into cheek pouches.
像大多数蝙蝠一样，它的膈膜不会延伸到脚踝， 因此它保持了水的清晰
The membrane doesn't go down to the ankle, like most bats', so it's kept clear of the water.
它的爪子像针一样尖利
And the claws are as sharp as needles.
但是它怎么知道什么地方能捕鱼呢？ 答案又是利用超声波
But how does it know where to trawl? The answer's ultrasounds again.
（蝙蝠的吱吱声）
(BAT CHIRRUPPING)
它能侦察到水面上鱼游过的波纹
It's able to detect the ripple of a fish at the surface
和死鱼的具体♥位♥置
and home in on it with deadly accuracy.
对于蝙蝠来说，捕鱼只需要很少的技能
But fishing, for the bats, is a rare and very recently acquired talent.
在哺乳动物中，第一个真正的捕鱼者
The first really accomplished fisherman amongst the mammals
最早出现在这一种群中
appeared early on in the history of the group.
当大型的远洋航行爬行动物，鱼龙和蛇颈龙
When the great ocean-going reptiles, the ichthyosaurs and plesiosaurs,
在恐龙时代消失时
disappeared at the end of the age of the dinosaurs,
哺乳动物就很快真正地
the mammals were very quick indeed
遍及整个世界只剩下了海洋
to fill the space that was left in the economy of the sea.
首先，毫无疑问的是， 有的动物有时生活在水中，有时生活在陆地上
At first, doubtless, the creature lived partly in the water, partly on land,
像今天的河马
rather as the hippopotamus does today,
但是，很快，在几十万年以内
but very soon, within a few million years,
真正的哺乳动物泳者出现了
truly specialised mammalian swimmers appeared.
一些长成鲸鱼，比最大的恐龙还要大
Some of them grew to be bigger even than the biggest of the dinosaurs: the whales.
在远离夏威夷的太平洋蓝色海水中
And here in the blue waters of the Pacific, off the Hawaiian islands,
每一年驼背鲸鱼都会聚集在这生产
every year humpback whales assemble to give birth and to court.
如果你有足够的耐心和幸运的话， 你可以游到它们中间去
And if you have a lot of patience and even more luck, you may be able to swim among them.
我很幸运可以和鲸鱼专家一起潜水
I was lucky enough to dive with a group of whale experts
他们知道怎样可以接近那些庞大的动物
who knew just how to get close to these magnificent creatures.
在远处，有一个四十吨♥重的母亲和它的孩子
And there, in the distance, a 40-ton mother and her baby.
发生在这种巨大动物上的血统变化