1·When their food supply is sufficiently large, the lemmings live a normal, undisturbed life.
当食物供给量足够大时，旅鼠过着正常、不受干扰的生活。
2·Great numbers of the lemmings begin a long and hard journey across the Scandinavian plains, a journey that may last weeks.
大批旅鼠开始了穿越斯堪的纳维亚平原的漫长而艰难的旅程，这段旅程可能持续数周。
3·A common theory for this unusual phenomenon is that the lemmings do not realize that the ocean is such a huge body of water.
对于这种不寻常的现象，一个普遍的理论是，旅鼠没有意识到海洋是如此巨大的一片水域。
4·Populations of lemmings, caribou and red knot (a shorebird) have all decreased.
旅鼠，驯鹿和红腹滨鹬(一种滨鸟)的种群数量都有所下降。
5·And the lemmings head in the opposite direction.
而在相反的方向旅鼠头。