All they can do is continue their migration 它们只能继续迁徙
They have no choice but to back down 它们别无选择 只得退下
Instead, they bide their time, waiting for the right moment. 相反 它们耐心等待时机
They are guided by an old female, the matriarch, 它们由一头年长的雌性即女族长带领
for they can look forward to the end of winter 因为可以期待冬天的结束
they need little energy to keep warm... 所以它们不需要多少能量 就能保持温暖
they use oxygen far more effectively than Maiacetus. 它们利用氧气的效率远高于慈母鲸
But unlike whales, they still spend much of their time lazing on land. 但与鲸不同 它们多数时间仍懒洋洋地躺在陆地上
It's in the water that they come alive... 在水中 它们才会活跃起来