but once a year they come together to have their young. 然而 每年总有一次 这些它们将会聚集在一起 繁衍后代

18. Mongolian gazelle.
    蒙古瞪羚
19. Two million are thought to live here, but no one really knows.
    共约两百万只瞪羚生活在此处 但具体数量仍不得知
20. For much of the time, they're scattered through this vast landscape,
    瞪羚在大部分时间里 都各自流浪在这片广袤的大地上
21. but once a year they come together to have their young.
    然而 每年总有一次 这些它们将会聚集在一起 繁衍后代
22. Nearly all will give birth within the next 10 days.
    在接下来的十天之内 几乎所有的小家伙都会呱呱坠地
23. 0ut in the open, communal calving is the safest way to have young.
    在毫无遮挡的草原上若想安全地繁衍 最佳方法是集体照看
24. With so many pairs of eyes keeping watch,
    有了这么多双警惕的眼睛

来自《行星地球 第一季 第七集 Planet Earth S01E07 伟大草原》第 21 行