By Sara Shipley Hiles

Monarch Butterfly, © Jim Brandenburg/Minden Pictures

© Jim Brandenburg/Minden Pictures
Like wildebeest on the Serengeti or salmon in the Pacific Northwest, monarch butterflies take part in an epic migration.

Each fall, hundreds of millions of monarchs sweep down from eastern Canada and the United States to the mountains of central Mexico, where they spend the winter clustered in fir trees. The following spring, they turn northward again. Researchers don’t know how such small organisms can travel so far, or how the butterflies navigate during their journey of up to 3,000 miles. Do monarchs fly along certain routes? How does weather affect them? And, most importantly, why are their numbers declining?

Through the Monarch Watch program headquartered at the University of Kansas, thousands of volunteers across the butterfly’s range are tracking the migration to help understand and protect these elegant insects. The volunteers capture migrating monarchs and tag them with small identification stickers. A tag recovered in Mexico earns a reward of 50 pesos (about $5).

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But since Monarch Watch director Chip Taylor founded the program in 1992, the size of the winter colonies—measured by the amount of land the butterflies occupy—has shrunk significantly, from just over 22 acres to just under 15 acres. “I find it alarming,” says Taylor.

Habitat loss is a major problem for monarchs, which need milkweed plants to lay their eggs and nectar-producing plants for food. Development paves over 2.2 million acres of land a year in the United States, Taylor says. The use of herbicide-resistant genetically modified soybeans has eliminated another 100 million acres of habitat since 1997. In Mexico, illegal logging has eliminated some overwintering sites. And then there is climate change, which threatens to disrupt the monarchs’ temperature-sensitive life cycle. “How much more can we lose without having a significant impact on monarchs?” Taylor asks.

To help replace some of this lost habitat, Monarch Watch created the monarch waystation program in 2005 to encourage people to plant milkweeds and other butterfly-friendly plants in their backyards. Meanwhile, an army of volunteers fights to keep the migration going. Monarch Watch’s educational outreach program involves more than 2,000 schools and other organizations, and more than 100,000 people help with tagging each fall. Tagging kits cost $15. Participants receive instructions, small ID stickers and a data sheet. The migration lasts from August to November, advancing southward about 25 to 30 miles a day.

Stay Informed
Fun facts and a video about monarchs

Naturalist Corinne Mastey led a group of volunteers in tagging monarchs last September at Bernheim Arboretum and Research Forest in Clermont, Kentucky, near Louisville. Armed with a mesh net, Mastey waded through a sea of grasses and plants, capturing her quarry with a quick flick of the wrist, saying, “If you chase a monarch with a net and you miss it, it probably won’t give you a second chance.”

Carol Hyatt, a butterfly enthusiast and retired occupational therapist from Louisville, who “tagged” along, was amazed at Mastey’s skill. “I couldn’t believe she said she was going to tag butterflies,” Hyatt says. “It’s hard enough to tag a bird.”

Contrary to popular belief, Mastey says, touching a butterfly won’t hurt it, demonstrating how to remove a butterfly from the net and place a small round sticker about the size of a pencil eraser on its hind wing. Soon the butterfly fluttered on its way.

Migrating monarchs live for eight or nine months, compared to just two to five weeks for monarchs at other life stages. The butterflies conserve energy by gliding on air currents, stopping to sip nectar for energy. Monarchs west of the Rocky Mountains migrate to the California coast. Those east of the Rockies travel to Mexico.

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Learn about Defenders’ efforts to safeguard habitat for imperiled creatures like monarch butterflies.

Mountain forests there provide an ideal microclimate. Temperatures hover just above freezing, letting monarchs slow their metabolism to a semi-dormant state. Sunny days warm the butterflies enough so they can briefly leave the roost for nearby water sources.

In the spring, monarchs mate and begin the return trip. Females lay eggs on milkweed plants as they fly northward, beginning a recolonization of their former range that will take two generations to complete. It will be their great-great-grandchildren that return to the Mexican wintering sites in the fall, where Taylor has witnessed massive numbers of butterflies dying of sheer exhaustion after arrival.

“Talk about the drive to replicate that nature demonstrates,” he says. “This is one of the most graphic, most amazing things I’ve seen.”

See how you can participate in monarch butterfly tagging or learn how to plant butterfly-friendly plants in your backyard.

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