Within days they will have to keep up with their parents 几天内他们就将跟随自己的父母

285. As the calves appear,
     小鹿出生的时候
286. so too do the leaves of the newly sprouting grass.
     也正是青草发新芽的时候
287. And the calves must strengthen quickly.
     幼鹿必须迅速增强体能
288. Within days they will have to keep up with their parents
     几天内他们就将跟随自己的父母
289. on a never-ending march.
     踏上无尽的征程
290. At one day old, they're already faster than an Olympic sprinter.
     第一天 他们的速度就已经超过人类短跑健将
291. They're testing the legs that will carry them thousands of miles,
     他们正在测试自己跋山涉水用的四肢

来自《行星地球 第二季 第五集 Planet Earth S02E05 草原》第 288 行