Cold snaps trigger Monarch butterfly migrations [1]

science.nbcnews.com-2/21/2013, Elizabeth Howell

Cold weather in the Mexico mountaintops, where monarchs spend the winter, triggers the butterflies' migration northward, according to new research.

The finding raises troubling implications, researchers said, for how the approximately half-billion migratory butterflies [2] will find their way if climate change unduly warms the mountains.

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