Only then do they close in behind the herd. 这时他们才从背后接近野牛群

238. and using carefully placed stone stacks,
     使用精心摆放的石堆
239. hunters corralled the bison for miles,
     猎手们将野牛驱赶数公里
240. until they were exactly where they wanted them.
     直到它们落入埋伏
241. Only then do they close in behind the herd.
     这时他们才从背后接近野牛群
242. Reveal themselves too soon
     如果太早暴露
243. and days of effort will be wasted.
     多日的努力将付诸东流
244. Their ultimate prize isn't the death of one,
     他们最终的目标不是杀死一只

来自《我们星球上的生命 第一季 第八集 Life on Our Planet S01E08 冰与火的世纪》第 241 行