生命的进化（1979）

and it had four toes on its front legs and three on the back.
像巴塔哥尼亚野兔，它靠速度寻找安全
Like the mara, it sought safety in speed.
更长的腿，更大的步幅就能尽可能地跑得快
The longer your legs, the longer strides you can take and the faster you can run.
一代一代的动物
Over generations these creatures
通过提高脚趾的高度增加腿的长度
increased the length of their legs by rising up on their toes.
数百万年后，一些进化了的动物 把它们身体的重量单独放到脚趾中♥央♥
After millions of years some developed which carried their body weight
脚趾几乎不碰到地面
on the middle toe alone, and the side toes barely touched the ground.
它们脚趾中间持续生长的指甲变厚减少磨损： 蹄子
Their continuously growing nail on the middle toe became thick to reduce wear: a hoof.
最后脚趾面终于完全消失。 这些是早期的马
Eventually the side toes disappeared altogether. These were the early horses,
它们遍及北半球，并且南到非洲
and they spread right across the northern hemisphere and down into Africa.
斑马，把它们的长腿连接到坚硬的脊椎上
Zebras, with their long legs jointed to a stiff backbone,
以每小时65千米40英尺的速度奔驰
can gallop at speeds of up to 40 miles, 65km an hour.
它们为了安全以小组为单位奔跑
They run in groups for the safety in numbers.
意外抓获一只斑马是很难的 如果这只斑马在小组里，
It's more difficult to take an animal by surprise if it's in a group,
并且像这样，大量聚集在一起能够迷惑猎食者
and a swirling mass, like this, makes a very confusing target.
其他草原上的食草动物 以不同方式寻求免遭捕获的保护
Other grass-eaters on the plains find protection from hunters in different ways.
犀牛像哺乳动物一样牢固的皮
The rhinoceros has a hide as tough as any mammal's,
用来抵御锋利的爪子和牙齿
proof against the sharpest claws and teeth.
它庞大的体积也使它很令人畏惧
Its sheer bulk makes it very formidable, too.
这也帮助它解决了吃嫩叶的动物面临的问题
But that also helps it with the universal problem for browsers,
就是如何消化纤维素
how to digest cellulose.
犀牛不能咀嚼反刍食物
The rhinoceros doesn't chew cud.
而实际上是把食物放在胃里很长时间
Instead it keeps its food in its belly for a very long time indeed,
以至于那些细菌有大量的时间去消化它
so that the bacteria have plenty of time to work on it.
为此，你需要很大的胃去存储这些食物
To do that, you need a very large belly in which to store the food,
如果你准备搬运一个很大的胃 那么你必须很大
and if you are to carry a large belly, you must be big.
在草原上仅有一种动物比犀牛大得多
Only one creature on the plains is much bigger than the rhino.
大象是活着的最大的动物
The elephant is the largest land animal alive,
它的巨大体型使得它不受伤害
and its huge size makes it virtually invulnerable.
没有一个猎手有足够大或足够强 去推倒一头成年大象
No hunter is big enough or powerful enough to pull down a full-grown elephant.
它是如此大，几乎不能得到任何树的树荫， 有时候分散在草原上
It's so big, it hardly gets any shade from any of the trees occasionally studding the plains,
并在太阳的照射下它陷入过热的危险中
and out in the baking sun it's in danger of getting overheated.
扇动耳朵帮助它冷却血液
Flapping its ears helps considerably in cooling the blood,
因为它通过它耳朵的纹理
as it passes through the veins of the ears.
大象设法活在哺乳动物最缺乏食物的地方
The elephant manages to live on what is probably the poorest diet of any mammal.
虽然它喜欢树叶 当它能获得时
Although it welcomes leaves when it can get them,
但它也吃极富纤维素的树枝、树皮甚至树干
it also eats the most fibrous browse of all, twigs, bark, even branches.
但是再一次，它巨大的肠子 允许给予这些粗糙的食物很长的化学反应时间
But again its huge intestines allow it to give this roughage prolonged chemical treatment.
我们要花一天来消化我们体内的食物
Our food takes about a day to pass through our bodies.
一头大象却要花两天半
An elephant's takes two and a half days.
因为大多数时候食物已经被大象用臼牙嚼碎了
For most of that time, the browse, having been mashed by the elephant's molars,
在内脏里的消化液与细菌群落的作用下消化
is stewing in the digestive juices and bacterial broth of its gigantic gut.
森林羚羊也跑到了开阔地
Forest antelopes also moved out into the open country,
被如此多的容易得到的植物所吸引
lured by so much readily available vegetation.
这种小羚羊在很多方面与早期的 在森林中生活的羚羊类似
The little dik-dik resembles the early forest-living antelopes in many ways.
像它们一样，很小，只有一英尺高 以便在茂密的植物中移♥动♥
Like them, it's small, only a foot high, which is convenient for moving in thick vegetation.
它们成对生活， 由于在热带雨林遮阴的地方很缺乏树叶
And it lives in pairs, for the shaded floor of the tropical forest is poor in leaves
无法喂养大量的食草动物
and can't sustain a dense population of leaf-eaters.
所以羚羊生活在那里
So the antelopes living there
标记并保卫它们珍贵的草原，对付竞争者
mark and defend their precious pastures against rivals.
雄羚羊把眼睛下面腺体产生的麝香涂在树枝上
The male deposits musk from a gland beneath his eye on twigs
使树梢在腺体上摩擦
by poking the tips actually in the gland.
这种气味表明这块领地只属于这一对
The scent proclaims that the territory belongs to a particular pair,
它们将呆在这个地方共度一生
which will remain here together throughout their lives.
另一只雄正在识别这种气味
Another male reads the signs.
气味对犬羚非常重要
Smell is very important to the dik-dik.
它们的蹄有其他的气味腺
They have other scent glands between their hooves,
可以标记路线
which probably mark the trails.
然而在一块地方上从不迷路
Since the pair never stray from this one patch of land,
它们很清楚这一点， 那是很重要的防御
they know it intimately, and that's important in defence.
当危险逼近时
When danger approaches,
它们知道最好的逃跑路线， 最好的隐藏角落
they know the best escape routes, the best corners in which to hide.
黑斑羚居住在更广阔的野外
Impala inhabit more open country.
它们不再成对生活，而是为了安全组成兽群
They no longer live in pairs, but have formed herds for safety's sake.
意外捕获它们是很困难的
It's very difficult to take them by surprise.
当它们受到袭击时，它们群体合作，挡住攻击者
When they are attacked, the herd works together to baffle their assailants.
同时它们从各个方向突然跳跃
As the animals suddenly leap in all directions,
猎手将很犹豫它要跟随哪个方向
a hunter may well hesitate in deciding which it should follow,
很难区别猎物和逃跑者
and that may make the difference between a killing and an escape.
黑斑羚更喜欢有灌木丛和树的野外
Impala still prefer country containing bushes and trees,
但一些食草动物把它们的生命完全暴露在野外
but some grazers spend all their lives exposed
没有任何掩护
out on the open plain, where there is no cover of any kind.
牛羚形成了最大的群体之一
The wildebeest form some of the greatest herds of all.
好几万的动物穿越草原
Tens of thousands of animals move across the plains,
有时在雨季过后做长途旅行
sometimes making huge journeys to follow the rains
去找刚发芽的草
and find the newly springing grass.
在这样巨大的队伍中没有成对的雌雄动物
In vast assemblages like these, there are no pairs of males and females.
在发♥情♥期，具有统治地位的公牛 将会建立一个小的有标识的地方
During the rutting season the dominant bulls will set up small stamping grounds,
母牛将会一个接着一个地来拜访
which the females will visit one after the other.
所以一头单独的公牛将会拥有很多母牛
So a single bull will service many cows
然后将会与她们失去联♥系♥
and then lose touch with them as individuals
当她们回到某个不为人知的群体
when they return to the anonymity of the herd.
不出人意料，这个高度集中的群体
Not surprisingly, this immense concentration of animals,
巨大的肉类储备吸引着猎手的注意
this vast reserve of meat, attracts the attention of hunters.
猎豹在径直追赶中依赖于它的速度
The cheetah relies on speed in a straightforward chase.
据说世界上最快的奔跑者 可以达到每小时110千米，70英尺
It's said to be the fastest runner in the world, capable of reaching 70 miles, 110km an hour.
它的腿不像羚羊那么长
It's legs are not as long as an antelope's,
但是它靠柔韧的脊椎增加腿的有效力量
but it increases their effective length with a backbone that's extremely flexible,
以至于它能跨很大的步
so that it can take huge strides.
但是它不能像这样长时间快速奔跑
But it can't sprint like this for long.
如果它没有在0.25英里范围内抓到猎物
If it doesn't catch its prey within a quarter of a mile,
那么它将疲惫地放弃
it has to give up exhausted.
这次，瞪羚获胜了
And this time, the gazelle has won.
小羚羊经常被猎豹捕食
Young wildebeest are often taken by cheetah.
这是一对雄性猎豹中的一只
This cheetah is one of a pair of males
在兽群中度步，好像几天来都在觅食
strolling through the herds, as if selecting their meal for the day.
但是很奇怪，这些羚羊看起来不是很担心
Oddly, perhaps, the wildebeest seem little concerned.
也许它们知道猎豹这种行为所代表的意义
Perhaps they know from the way the cheetahs are behaving
猎豹还不打算攻击
that they're not about to attack yet.
一只猎豹试探性地跑了一下
One male makes a tentative run.
弯曲他柔韧的脊骨 他可以跑出令人惊奇的23英尺，相当于7米远
Bending his supple spine, he can cover an astonishing 23 feet, 7 metres,
仅仅是一个跃起
in a single bound.
也许是用这个方法来干扰羚羊
It may be that by chivvying them in this way
猎豹试图抓比其他同类慢一点点的
the cheetahs are trying to pick out the animal that is just a little slower than the others,
容易被抓的羚羊
just a little more vulnerable.
他的爪子牢牢地抓住羚羊的气管
His jaws are clenched on its windpipe,
这只羚羊很快就被勒死了
and the wildebeest dies throttled.
另一只雄猎豹过来享用猎物
The other male comes to share the catch.
猎豹作为最擅长捕猎的动物 很少会捕捉比它们体积大的动物
Cheetahs, like most hunting species, rarely tackle prey larger than themselves.
但是狮子在这方面却不受限制 它们是群居的猎手
But lions are not so restricted. They are social hunters.
它们是草原上最巨大最重的猎手
They're the biggest, the heaviest of all the hunters on the plains,
并且它们通常是15只左右群居在一起
and they live in groups, usually about 15-strong,
而有时候它们会有30只左右群居在一起
though sometimes there may be over 30 in a pride.
它们跑得没有猎豹快 35公里每小时已经是最快的速度了
They're not as fast as the cheetah, about 35 miles an hour is their top speed,
在野外，它们对兽群不造成威胁
and out in the open they're no threat to the herds.
斑马可以保持它们的距离
The zebras can keep their distance.
倘若它们在受追赶时获得起跑的主动权， 狮子将永远抓不到它们
Provided they've got this amount of a start in a chase, the lions will never catch them.
狮子的唯一机会是靠得非常近
The lions' only chance is to get really close
然后依靠惊人的加速
and then rely on their spectacular acceleration.
现在一只狮子开始偷偷靠近了
Now one lioness begins to stalk,
低下身，在黄褐色的、晒得枯萎了的草中几乎看不见
keeping low and almost invisible in the tawny, sun-withered grass.
这只斑马发现了她
The zebra spot her.
在前面是其他的成员
Ahead there are other members of the pride.
在惊慌下，这只斑马跑向它们， 现在狮子捕捉到了猎物
In their panic the zebra run towards them, and now they take up the hunt.
但是尽管抓住了它 她单凭自己的力量不能制♥服♥它
But though she's got hold of it, she can't overpower it by herself.
其他的狮子过来帮忙
The others come to her aid.
现在得到食物了，不只是一只狮子的食物， 而是整个狮群的食物
Now there is food, not just for one hunter, but for the whole pride.
狮子以这样群体攻击的方法 平均每三次攻击中会有一次成功
Lions, hunting in groups like this, kill on average once in every three attempts.
但是狮子也不是总在一起狩猎
But lions do not always work in groups.
有时候狮子会单独行动
Sometimes a lioness will set out by herself.
单独行动中，五次里只有一次是成功的