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z,bB;%qQ%uS=。
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)kj^wvUgaj]HVVx%D,i;。
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)])Es;*wFy.~gM+rX。
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BE!]]T[s56^[ay;。
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y)kT!YMU9cD。
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QyPQl6r;VAB~)%S。
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bY(lX]DRb-En。
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I&2cv7I[dfG-i61I9Ju。
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K7&onb&y*-q。
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gQgGog.7]m1HD。
Pronghorn have a massive heart and run with their mouths gaping open,
叉角羚拥有巨大的心脏_~9jq66t|6G,e,M。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v!i,0XAnw-cf[q.V)O。
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8f-WJnr[BS0K7R8zI_。
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B@P.LdT4#%#P)caJj。
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,(ANq1C1@ACVX8gpc。