Journey North: Monarch Butterfly

What Scientists Think . . .

Much more land is available in the monarch's breeding range than in its wintering range.* Over millions of years, monarchs have evolved to take advantage of the rich resources up north. Read on . . .

Sunlight. In late winter and spring, slowly increasing daylength triggers biological changes that tell monarchs, "It's time to go north." The sun's energy also melts ice and warms soil.
Food and Water. The sunlight, warmth, and spring rains cause milkweed to grow. This is the plant that monarchs depend on for survival. Monarch larvae cannot live without milkweed leaves for food; adults get food energy from the nectar.
Space. The great amount of land in the United States and Canada means that lots of milkweed (and other plants) can thrive and generations of monarchs can spread out, feed, and reproduce.

* The monarch breeding range in North America is nearly ten times the size of the monarch sanctuary region in Mexico!

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