and nourishing them on their mother's milk 用母亲的乳汁滋养幼崽

247. Crucial to the success of mammals
     哺乳动物成功的关键是
248. was the evolution of parental care.
     父母照护的进化
249. Giving birth to live young
     生下活的幼崽
250. and nourishing them on their mother's milk
     用母亲的乳汁滋养幼崽
251. until they reach independence.
     直到其独♥立♥
252. But for these nervous little youngsters...
     但对于这些紧张的幼崽们来说
253. that might take a while.
     这可能需要一段时间

来自《我们星球上的生命 第一季 第五集 Life on Our Planet S01E05 巨兽阴影下》第 250 行