The Monarch Butterflies' Mexican Vacation

The annual Fall monarch butterfly migration is an astounding thing. Hundreds of millions of orange-winged insects, traveling upwards of 30 miles a day, so that damn near every monarch in North America can converge on the same small patch of Mexico. In these over-wintering grounds, the monarch butterflies hang from the trees in clumps so thick that they look like dense leaves. You can end up with as many as 50 million butterflies on an area of land a little smaller than two-and-a-half soccer fields.

And what happens when all those butterflies wake up in Spring? In this clip from National Geographic's upcoming Great Migrations series, monarchs open their eyes, stretch their wings and proceed to get it on.