A lone wolf weighs as much as four coyotes,
一只狼的体重是草原狼的四倍，
but one on one it's still no match for a bison.
但是一对一，狼还是敌不过野牛VVXCC1g!(1R~1w#f。
Wolves, though, live and hunt in packs of up to 15
不过成员数最多可达15只的狼群，
and when they launch a cooperative attack, they're devastating.
只要同心协力发动攻击，将会无往不利n[)_k7E+tH_E。
First they get the bison on the run, then filter out the weak
一开始先让野牛开始狂奔，从中筛选出虚弱的，
and vulnerable and select the perfect target.
在挑选完美的目标Gg(jSqk(80)。
Striking together, wolves can bring down prey many times their own size.
群起而攻的狼群，可以绞杀打他们数倍的猎物)[bS7w||l)hruaU]3f。
A million such chases must have taken place across these plains
像这样的追逐在大草原上，必定发生过百万次，
and we can still find echoes of these distant life-or-death encounters.
我们仍然可以发现这些远古生死际遇的回生Jv_#5i4+qd。
Not all evidence lies locked in bone and rock.
并非所有证据都封存在骨头或石头中63ThV~NSW(H-g]6]#8。
These pronghorn antelopes among the great survivors of the ice age reveal a lot about the distant past.
这些叉角羚也是雄奇的冰河期生还者之一，揭示着许多远古的记忆*RBZAG;Ezn。
As well as being tough enough to stand extremes of temperature, they're famous for their speed.
他们坚毅强悍，足以撑过极为严寒的气温，并以它们的速度闻名itU_LvSe5v4LqjDva。
A sprinting pronghorn can top 60 miles an hour and cruise at 30 for several hours.
飞奔中的叉角羚时速可快达60英里，还能以30英里的时速续跑数个小时Ch00T(Kf&5Pa。
This kind of speed requires a very finely tuned physique.
这样的奔驰速度需要非常优越的完美体格*Dw~6@yj&%nyaG]FR。
Pronghorn have a massive heart and run with their mouths gaping open,
叉角羚拥有巨大的心脏,)n9IcSX,Xs。奔跑的时候，长大着嘴，
forcing extra air into their huge lungs.
吸入更多的空气进入巨大的肺部zgN&|SPv]Cf。
But what's the point? No predator can run this fast.
重点何在呢？没有掠食者能跑这么快[qV@^t=#ij_!。
Even the wolves can only manage 40 miles an hour.
就连狼跑起来最快也只有时速40英里KEuo*DX57K1Ygw。
So why do pronghorn feel this need for speed?
为什么叉角羚需要这样的速度呢？
This is why—once there was a predator here that could outrun the pronghorn a cheetah.
这就是答案: 这里曾经有过一种掠食者，可以追的上叉角羚和猎豹SL^J_HrX]nHaGz]]1。