The Magnificent Migration of the Monarch Butterflies

These winged beauties take over Mexican jungles every winter. | By NGT Staff  
Monarch Butterflies
Millions of monarchs spend the winter on oyamel, a kind of fir tree, in central Mexico. Their metabolism slows down on cold days but they flutter around when it’s warm. Photo: Sunmallia Photography/Flickr/Getty Images

There’s a major wildlife exodus taking place on the other side of the world right now. About one billion monarch butterflies are leaving their winter hibernation spots in Mexico and California and heading back home to the northern parts of the United States and Canada. At 4,800 kilometres, it’s the longest insect migration in the world. This epic journey begins in late August, when the orange-and-black butterflies fill up on nectar to prepare for the long road ahead to southern warmth. In March, when it’s spring in the north again, the delicate creatures will begin their flight back home: laying eggs on milkweed plants along the way.

It’s most dramatic. The generation that started the trip in August usually dies after laying their eggs, but their young continue the journey their parents began. The butterflies that finally make it back to the start are usually great-grandchildren of the ones that started. But come winter, the monarchs born in August-September head to the same wintering grounds where their ancestors spent the cold season, even though several generations in between have never been to those places. The precision with which they return to the same place each year has puzzled researchers for years.

The ideal time to go see butterflies is in winter, during the hibernation period, when their metabolism has slowed down and they cluster by the thousand. Branches of trees have been known to collapse with their weight. For those not fortunate enough to view this phenomenon in person, there’s always technology. An immersive 360° video from National Geographic plants the viewer right in the middle of a Mexican forest that has been taken over by monarch butterflies. (Move your cursor around the screen for maximum magic!)

Appeared in the September 2013 issue as “Wing Power”.

Where to See Monarch Butterflies

Wintering grounds are best visited on warm days between November and February, when millions of brown and orange wings fill the trees and sky.

Mexico Head to El Rosario Monarch Butterfly Reserve, Piedra Herrada Sanctuary, or Sierra Chincua Sanctuary in central Mexico, west of Mexico City, to marvel at the roosting millions.

California
See them at the Coronado Butterfly Preserve in Santa Barbara, Presidio Park in San Diego, and Monarch Butterfly Grove in Pismo Beach.

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