旅鼠在同一时间倾巢而出，形成了庞大的鼠群。
The lemmings leave their nests all together at the same time, forming huge crowds.
当旅鼠的食物供应不足以维持种群时，一次特别的迁徙就开始了。
When the lemmings' food supply becomes too low to support the population, a singular migration commences.
然而，当旅鼠的食物供应变得太少而无法维持种群时，一次特别的迁徙就开始了。
However, when the lemmings' food supply becomes too low to support the population, a singular migration commences.
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。
Great numbers of the lemmings begin a long and hard journey across the Scandinavian plains, a journey that may last weeks.
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。
A common theory for this unusual phenomenon is that the lemmings do not realize that the ocean is such a huge body of water.
最后，请不要提旅鼠。
旅鼠，驯鹿和红腹滨鹬(一种滨鸟)的种群数量都有所下降。
Populations of lemmings, caribou and red knot (a shorebird) have all decreased.
黄鼠狼和旅鼠开始改变颜色，随着深冬的来临，它们的毛皮将会变成雪白色。
The weasel and the lemming begin to change color; as the winter deepens, their coats will turn snow-white.
不仅如此，许多生活在寒带陆地上的动物，如旅鼠、驯鹿和雪号鸟等，也将被挤到一个更为狭窄的区域中去。
On land, creatures like lemmings, caribou, reindeer and snowy owls are being squeezed north into a narrower range.
这简直是太像那些为了行动而动的旅鼠了，而我，则一向是以自己的真实而骄傲的，哪怕有时这意味着我要打破某些规矩。
There is just something a bit too lemming-like about that course of action and I've always taken pride in being true to who I am even if that means I must break with the norm.
由于体型较大且较具优势的红狐北移，北极狐在苔原南部的数量正在下降，而且他们的猎物旅鼠也因为气温上升而越来越少。
The Arctic fox is disappearing from the southern edge of the tundra as larger, more dominant red foxes move northward and lemming prey grow less abundant as temperatures warm.
由于体型较大且较具优势的红狐北移，北极狐在苔原南部的数量正在下降，而且他们的猎物旅鼠也因为气温上升而越来越少。
The Arctic fox is disappearing from the southern edge of the tundra as larger, more dominant red foxes move northward and lemming prey grow less abundant as temperatures warm.
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