In the United States and Canada, monarchs live only six to eight weeks from egg to caterpillar to butterfly. In Michoacán, though, the migrating generations live up to nine months, mostly in blissful slumber.
The tiny insects are astonishing travelers. They can go 80 miles a day, traveling an average of 12 miles per hour, and if the winds are right, they cruise at an altitude of two miles. They travel during the day, living off their stored fat, and stop to eat only if there are flowers. If it is foggy or cloudy, they stay put, preferring to move only during bright, sunny weather. But why do they hibernate in Mexico? For centuries, locals believed the annual butterfly swarms were some sort of plagues, and they killed as many of the insects as they could. The more superstitious believe that the monarchs come to this area to visit their dead ancestors.
Another popular rumor is that a magnetic field attracts the monarchs to these mountains -- tantalizing but not true. The real reason is more obvious, says Alfredo: “Butterflies look for protection; that’s why they come here. There’s high elevation, they are protected by the tall trees’ branches, and there are flowers and water, so they don’t waste energy.”
While local indigenous tribes have always known about the mariposas monarcas, for a long time scientists in North America had no idea where the butterflies wintered. Each year, the swarms just seemed to disappear south of the Rio Grande . The mystery was finally solved in 1975, thanks to a clothing executive and a 12-year-old boy from Texas.
Volunteers had been tagging thousands of butterflies under the direction of Canadian entomologist Fred Urquhart. The thirty years of research indicated that migrating monarchs hibernate somewhere in Mexico, but Urquhart’s team was unsure of the location.
Ken Brugger, an American working in Mexico as chief engineer for Jockey underwear, had heard of Urquhart’s efforts. Being somewhat of an amateur naturalist, he offered to help and began his own inquiries with the locals. On January 2, 1975, Brugger and his wife scaled the slopes of a Michoacán summit called Cerro Pelón and there discovered millions of hibernating butterflies clinging to the trees.
The Bruggers eagerly picked through the colony to find any monarchs that might have been tagged in North America and could thus establish conclusively the exact migration route. They were having little luck until they came upon one butterfly that stood out from all the rest. It was significantly larger. And it had a tag. With a phone number.
Surprisingly enough, though, it wasn’t one of Urquhart’s tags. Instead, it belonged to 12-year-old John McClusky, who had been tagging butterflies in Fredericksburg, Texas, for several years. He had read about the migrations and then written his own labels and tagged the butterflies all by himself.
“I didn’t know there were any professionals doing it,” says McClusky, now a chemistry professor at Texas Lutheran University. “I was hoping that someone would find them. [But] I didn’t really know I was contributing to science.
“Ken Brugger called my home from Mexico,” he recalls. “They were [so] excited. They’d found what they’d been looking for all those years.”
Alfredo and I pass through an open meadow ringed by forest. Monarchs circle lazily above us, casting their shadows on the ground. The trail turns back to the forest, and Alfredo begins to move very carefully, motioning for me to do the same. While monarchs are completely deaf, they can detect light and movement, and they have a terrific sense of smell.
Within moments, dozens of butterflies clinging to bushes quickly flutter away just out of our reach. The treetop canopy above bustles with tiny flashes of orange. We’ve been detected.