叉角羚

现代的叉角羚（美洲羚羊）仍然是一个谜。

The modern pronghorn ( American antelope ) presents a puzzle .

但是这位母亲叉角羚在放牧的时候必须离开她的小牛犊们。

But the mother pronghorn must leave her calves alone while she grazes .

由一个属构成的叉角羚科的模式属。

Type and sole genus of the Antilocapridae comprising one species .

和叉角羚一样，敏锐的感官使得跳羚十分机警。

Like pronghorns , springbok are very agile with sharp senses .

那么叉角羚为什么会进化出这么快的速度呢？

Why did the pronghorn evolve such speed ?

要想了解这些生物，我们首先来看看谜一般的叉角羚。

To learn about those , we turn to the mystery of the pronghorn .

美洲羚羊，或称叉角羚，是该大陆典型的草原植物。

Typical of the grassland dwellers of the continent is the American antelope , or pronghorn .

叉角羚卓越的奔跑能力与生俱来，它们的弹跳能力也十分惊人，尤其身处巨大压力时。

Pronghorns are designed for running , but sometimes they can accomplish amazing jumps , especially under immense pressure .

在理论上就可以将叉角羚放回在其自然那的进化轨迹上来。

in theory , put the pronghorn back onto its ... uh , natural evolutionary trajectory according to these biologists .

答案在于叉角羚进化时所处的环境远比现在的环境更加危险。

The answer is that the world in which the pronghorn evolved was a much more dangerous place than ours .

当美洲印度豹绝种以后，它们对叉角羚及其他可能猎食的动物进化的影响就停止了。

When the American cheetahs disappeared , their influence on the evolution of pronghorn and presumably on other prey animals stopped .

此外叉角羚的骨架十分轻盈，运动灵活，体表的毛发也不多，这样在奔跑时就不会大量出汗消耗能量。

Their bone structure is light , making them very flexible , and they have minimal hair to reduce profuse sweating .

但是叉角羚的视力非常好，它们很不喜欢身边有陌生人，所以里斯架设起了动态捕捉照相机。上面的照片就是这样拍摄的。

But pronghorn have tremendous vision and are not fond of strangers , so Riis set up motion-triggered cameras to capture pictures like this .

所以可以想象，如果印度豹还存在的话，叉角羚本可以继续进化，跑的更快。

So it is conceivable that the pronghorn antelope would have continued to evolve , get faster maybe , if the cheetahs were still around .

我们之前见识到了跑得飞快的以叉角羚为食的各种猎食动物，现在马上就会看到另一种残暴的食肉动物，一种长得很像现代狼的长腿土狼。

The predators we met earlier , the fleet-footed creatures who may have preyed on the pronghorn , were joined by another terrifying carnivore , a long-limbed hyena that resembled a modern wolf .

我们相信它在叉角羚的进化中起重要的作用，精确来讲，羚羊惊人的速度是一种自然选择的结果，因为只有能跑过印度豹的羚羊才能生存下来。

We believe it played a pivotal role in the evolution of the pronghorn antelope , the antelope 's amazing speed , to be exact , because natural selection would favor those antelope that could outrun a cheetah .