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.
当食物供给量足够大时，旅鼠过着正常、不受干扰的生活。
When their food supply is sufficiently large, the lemmings live a normal, undisturbed life.
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。
冬季为白色皮毛且一些爪非常大的北美洲旅鼠。
North American lemming having a white winter coat and some claws much enlarged.
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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