Texas Parks & Wildlife Magazine   

Archives

October 2009 cover image lesser prairie-chicken

Monarch Mania

Each October Texans witness an amazing natural phenomenon—in their own backyards.

By Elaine Robbins

Sure, Mike Bessire raises cows on his ranch near Abilene, but it’s really butterflies, not Brangus cattle, that get him excited. Each year a growing crowd of friends and family gathers for the show.

“They are here!” he wrote last fall in a posting to Journey North, a monarch migration website. “For the seventh year in a row we have monarchs in mass numbers roosting in the tall willow trees. The preliminary count is as low as 12,500 and as high as 25,000!”

Up to 300 million monarchs migrate annually through Texas. They fly in from Maine to Minnesota, from across the eastern United States and southern Canada, they funnel down to a 300 mile-wide central flyway through Texas centered on Wichita Falls [through Abilene, San Angelo and on to Del Rio] (A smaller migration route follows the gulf coast.)

Where are all those monarchs heading? To their wintering roosts in the oyamel forest of Michoacán, in central Mexico.

Last fall, a week after the monarchs left Bessire’s ranch, they flitted through Helen Cordes’ backyard in Georgetown, where she was having lunch with her daughter Zoe.

“We watched for at least 15 to 30 minutes when a dozen at a time flew by,” she says. “They seemed to be flying a route that went right down our street. It was one of the most amazing things I’ve ever seen in my life.”

A few days later, they were gliding high on a thermal over Sabinal Canyon, where Mitch Heindel watched them through binoculars near his home in Utopia.

“I saw one, then an hour later 10, then 100,” he recalls. “I’m standing at one edge of this river of monarchs. The river could be miles wide and who knows how many miles long. Like the wildebeest or whale migration, it’s hard not to be overwhelmed by the energy of life you’re getting to witness.”

A week later Carol Cullar saw them crossing into Mexico while she was taking a Sunday-school class on a canoe trip down the Rio Grande. “There was a continuous stream of monarchs flowing across the river into Mexico,” she posted on the website Monarch Watch. “We probably saw between 500 and 700 an hour. Our canoes and the monarchs were fighting a stiff southeast wind gusting up to 35 miles per hour.”

Entomologist Mike Quinn, who leads Texas Monarch Watch (www.texasento.net/dplex.htm), is amazed by the monarch mania that descends on Texas each fall. Like most insect scientists, he has come to accept the fact that some of his research doesn’t generate much excitement among the general public. But each October when the monarchs arrive, his phone starts ringing off the hook. Reporters call from across the state, clamoring for quotes. His e-mail inbox fills up with reported sightings.

The mania reached its height the year that the migration went straight through the Dallas/Fort Worth metroplex. “I had people calling from the 20th floor of high-rise apartment buildings to say that the monarchs had just flown past their windows. Downtown office workers called and said, ‘Come get your monarchs. They’re distracting me from my work.’”

Quinn believes that it is not just their trademark beauty but also the unfathomable challenge of their journey that inspires such rapture.

“They weigh half a gram and can fly as far as 3,000 miles,” says Quinn. “This is something no technology can match — our brains can’t even understand it. It’s something that will forever be of fascination.”

To save energy, monarchs ride on tailwinds and glide on thermals for long stretches of their journey. So effective is this approach that monarchs, scientists were surprised to find, weigh more at the end of their journey than at the start.

“The other mind-boggling aspect is that it takes three to five generations to make the yearly round trip,” says Quinn. “No one butterfly goes all the way around. They’re gathering in Mexico by the hundreds of millions, and not a single one of them has been there before.”

In the world’s longest relay race, the southward-bound generation flies all the way to Mexico, where it overwinters in a torpid state and then starts the journey north in the spring. That overwintering ­generation lives up to eight months — a very long time for an adult insect. Heading back north in the spring, they lay eggs and die, and the next generation picks up the baton.

It takes two more generations to complete the northward journey, each living just four to six weeks. The fourth generation, cued by the angle of the sun that cold weather is coming, makes the long journey to the Mexican wintering grounds, continuing the ancient cycle.

 

monarch butterflies

How butterflies from across the country find their way to a 70-square-mile forest in Mexico is still a subject of debate. Like birds, monarchs are thought to navigate using the angle of the sun, the earth’s magnetic field and landmarks. When they hit the Sierra Madre Orientals in Mexico, for example, they follow the mountains 900 miles south to their winter roost.

But the clever monarch has another trick up its sleeve: It is one of the few insects that can navigate longitude as well as latitude. Latitude is a fairly simple proposition, involving gauging one’s position based on the location of the sun or stars. But longitude is a more vexing problem, one that challenged humans for centuries. Explorers constantly missed their marks until the invention of the marine chronometer, which could simultaneously track their current time against Greenwich Mean Time. Steven M. Reppert, chair of neurobiology at the University of Massachusetts Medical School, recently discovered that the monarch, with a brain smaller than a pinhead, indeed has a circadian clock that communicates with an internal time-compensated sun compass to aid navigation.

For 100 years another mystery puzzled scientists: Where did the monarchs go when they disappeared in the fall? In the 1870s naturalists first theorized that monarchs might migrate like birds. Their theories were mostly speculative until 1938, when Fred Urquhart, a zoology professor at the University of Toronto, started tagging monarchs to track their movements. Eventually he and his wife developed a network of 3,000 volunteers throughout North America to tag the butterflies and report the locations of found individuals. By 1972 a pattern started to emerge as the first tagged monarchs from the eastern United States and Canada turned up in central Mexico.

The final breakthrough occurred in 1975, when Ken Brugger, an American research associate of Urquhart’s who was working in Mexico City, discovered their roosting place. Working on tips from local loggers and from his Mexican wife, Catalina, who recalled seeing the monarchs as a child when she brought lunch up the mountains to her grandfather, he climbed to the oyamel fir forest at 10,000 feet in Michoacán.

What he saw there would amaze the thousands of monarch pilgrims who would follow in his footsteps. Millions of butterflies covered the trunks of tall trees and hung in clusters on branches like fall leaves.

Urquhart announced the discovery in an article in the August 1976 issue of National Geographic. It was “among the greatest biological finds of the century,” writes Eric Grace in The World of the Monarch Butterfly, “a zoological equivalent of the tomb of Tutankhamun, a treasure trove of history and beauty combined.”

The excitement of the discovery was followed several years later by alarm when monarch biologists reported that logging was taking a toll on the butterflies’ oyamel forest. In response to an international public outcry, in 1986 the Mexican government declared the monarchs’ winter roost an official sanctuary. Today visitors from all over the world climb the mountains to listen to the sound of millions of flapping wings in the sanctuary. But illegal logging continues to be a threat because it cuts holes in the “thermal blanket” of the forest canopy, making the butterflies vulnerable to cold and rain. That threat led the World Conservation Union to declare the monarch migration the first “threatened biological phenomenon.”

While the migration does face real threats — both in Mexico, where grinding poverty provides a powerful incentive for logging, and in the United States, where agricultural herbicide use and suburban sprawl threaten the monarch caterpillar’s sole food plant, milkweed — reports of its death are greatly exaggerated, as Mark Twain once said. The monarch may be fragile, but it is also incredibly resilient. As it breeds across a wide swath of North America, it can take advantage of favorable conditions where they might occur. Most important, it has an impressive reproductive capacity, with each female laying about 300 to 400 eggs.

“The endangered whooping cranes still haven’t fully recovered after 60 years,” Quinn says, “but the monarchs can recover from a winter population drop in a year if conditions in the spring and summer are particularly favorable.”

In springtime, as the monarchs fly back through Texas, torn and tattered at the end of their life, mating is their sole imperative. The female finds a patch of milkweed to lay her eggs, which are pearly, textured jewels of pastel yellow.

In a few days, the caterpillar emerges. As the caterpillar chomps down milkweed and grows, it breaks out of its skin five times, eventually sporting stylish rings of black, white and bright yellow. Then it spins a pupa of shimmery spring green dotted with spots of metallic gold. One to two weeks later, the butterfly emerges, its trademark orange-and-black wings fringed with white-dotted borders.

The butterfly will spend its life in movement, claiming no territory of its own but making the whole continent its home. Its brief and beautiful life will be over in the flap of a wing. But if all goes well, the migration cycle will continue, inspiring all who see it with its sheer force of life.

back to top ^