Mystery of monarch migration takes new turn

Sun beams light the wings of monarchs resting in a tree in Mexico. Photo by Jaap de Roode.

By Carol Clark

During the fall, hundreds of millions of monarch butterflies living in eastern North America fly up to 1,500 miles to the volcanic forests of Mexico to spend the winter, while monarchs west of the Rocky Mountains fly to the California coast. The phenomenon is both spectacular and mysterious: How do the insects learn these particular routes and why do they stick to them?

A prevailing theory contends that eastern and western monarchs are genetically distinct, and that genetic mechanisms trigger their divergent migratory paths.

An analysis led by Emory University biologists, however, finds that the two groups of monarchs are genetically mixed. Their research, published in the journal Molecular Ecology, suggests that environmental factors may be the key to the butterflies’ choice of winter homes, and to where they wind up in the spring.

Fluttering monarchs fill the sky over Mexico. Photo by Jaap de Roode.

“Our data gives the strongest signal yet that the eastern and western monarchs belong to a single genetic population,” says Emory biologist Jaap de Roode, who led the research. “This distinction is important to help us better understand the behavior of the organism, and to conserve the monarch flyways.”

In addition to researchers in the de Roode lab, the study involved a scientist from the Institute of Integrative Biology in Zurich, Switzerland.

Biologists have long been fascinated by the innate and learned behaviors underlying animal migrations. When monarchs are breeding, for instance, they can live up to four weeks, but when they are migrating, they can live as long as six months.

“As the day length gets shorter, their sexual organs do not fully mature and they don’t put energy into reproduction. That enables them to fly long distances to warmer zones, and survive the winter,” de Roode says. “It’s one of the basic lessons in biology: Reproduction is very costly, and if you don’t use it, you can live much longer.”

Watch a YouTube video of monarchs gathering in Mexico, narrated in Spanish by Mexican actor Alan Estrada:


Mass movements of animals have huge ecological impacts. They are also visually arresting, from the spectacle of giant herds of wildebeest trekking across the Serengeti to hundreds of thousands of sandhill cranes flocking along the banks of Nebraska’s Platte River.

In the case of long-lived mammals and birds, the younger animals may learn some of the behaviors associated with migration. That’s not the case with the monarchs, notes Amanda Pierce, a graduate student in Emory’s Population Biology, Ecology and Evolution program, and a co-author of the study.

“We know there is no learning component for the butterflies, because each migration is separated by two to three generations,” Pierce says. “To me, that makes the problem even more interesting. How can these small, delicate animals travel thousands of kilometers and arrive at the same destination as their great-great grandparents?”

A tree in Mexico wears a fluttering cloak of monarchs. Photo by Jaap de Roode.

The question of whether eastern and western monarchs are genetically the same has been hotly debated, and may be an essential piece to the puzzle of their divergent migration patterns.

The researchers used 11 genetic markers to compare the genetic structures of eastern and western monarchs, as well as non-migratory monarch populations in Hawaii and New Zealand. The results showed extensive gene flow between the eastern and western monarchs, and a genetic divergence between these North American butterflies and those from Hawaii and New Zealand.

“In a sense, the genetic markers provide a DNA ‘fingerprint’ for the butterflies,” de Roode says. “Just by looking at this fingerprint, you can easily separate the butterflies of North America from those in Hawaii and New Zealand, but you can’t tell the difference between the eastern and western monarchs.”

The Emory researchers have now joined a project headed by Harvard, which also involves the University of Georgia and the University of Massachusetts, to sequence the full genomes of monarch butterflies from places around the world. That data should rule out genetic differences between the eastern and western monarchs, or reveal whether any smaller genetic differences, beyond the 11 markers used in the study, may be at play between the two groups.

Pismo Beach is a California overwintering site for monarchs. Photo by Jaap de Roode.

The idea that eastern and western monarchs are distinct populations has been bolstered by tagging-and-tracking efforts based in the United States. That data, gathered through citizen science, indicates that the butterflies stay on separate sides of the Rocky Mountains – a formidable high-altitude barrier.

De Roode, however, theorizes that when spring signals the eastern monarchs to leave the overwintering grounds in Mexico, they may simply keep radiating out, reproducing and expanding as long as they find milkweed plants, the food for their caterpillars.

“Few people have tagged the monarchs within Mexico to see where they go,” he says, “because Mexico doesn’t have as much citizen science as the U.S.”

If the theory is correct, some of the monarchs leaving Mexico each spring may wind up in western North America, while others may filter into the eastern United States. This influx to the western U.S. could be crucial to survival of monarchs on that side of the continental divide.

“There are far fewer monarchs west of the Rockies,” de Roode says. He notes that all of the overwintering monarchs on a typical overwintering site along the California coast consist of about the same number clustered onto a single big tree in Mexico’s Monarch Butterfly Biosphere Reserve, where hundreds of millions of monarchs blanket the landscape in the winter.

The monarch butterfly migration has been called an endangered phenomenon, due to the loss of habitat along the routes. The Mexican overwintering sites, located in the Trans-Mexican Volcanic Belt region northwest of Mexico City, particularly suffer from deforestation. Drug trafficking in the region has decimated eco-tourism and hampered efforts to protect the trees.

“We hope our research can aid in the conservation of the monarch flyways,” de Roode says.

Raising monarchs for release at weddings, memorials and other events is a growing industry, but U.S. Department of Agriculture regulations restrict shipping the butterflies across state lines.

De Roode stresses that this regulation should remain in force, even if further research confirms that eastern and western monarchs are genetically identical, because parasites that the butterflies carry can differ by region. “It’s not a good idea to be shipping parasites around,” he says.

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Cooking with acorns, painting with moss

Heather Buzzard says she likes to "hack away at the barriers between the indoors and outdoors."

By Mary Loftus, Emory Magazine

At Indie Fixx's TreeHouseHold, Emory graduate Heather Buzzard has written how-to pieces on making seed paper, cooking with acorns, and making moss spray paint—all of which might come in handy during her upcoming stint as artist in residence at the Hostel in the Forest, a spiritual sustainability and environmental education retreat center in Brunswick, Georgia.

Buzzard studied sociology, creative writing, religion, and environmental science at Emory. She cites a course called CORE, on religion and ecology, as particularly influential. “I’ve always been drawn intimately to the natural world,” Buzzard says, “but prior to the class, I hadn’t focused much on sharing that with others, being mindful of sacred space, and incorporating a sense of place and roots into how I live daily.”

At the Hostel in the Forest, she will be applying her understanding of sawdust composting toilets, solar panel water heaters, vegetable oil–powered lighting, organic gardening, and living off the grid.

“I like to take specific elements of the outdoors and integrate them into our everyday lives through sustainable art, design, and food, while focusing on the beauty and magic of the natural world,” she says.

And if you’re wondering if you really can cook with acorns, try her recipe.

Acorn Molasses Cakes

1/2 cup acorn flour

1/2 cup cashews, chopped


1/2 cup pecans or walnuts, chopped

1/2 cup raisins or dates

1 cup cooked brown rice

molasses (or honey) to taste

agave to taste

1/2 tsp cinnamon

1/4 tsp nutmeg
1/2 tsp ginger
a
pinch brown sugar or sucanat

Mix all ingredients together in large mixing bowl. Add enough molasses/honey so that concoction clumps together nicely without falling apart. Prepare a cookie sheet with parchment paper or a thin spread of butter, and ball the mixture together into smallish round cakes. Sprinkle the tops with brown sugar or sucanat. Bake at 325 for 10–15 minutes.

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Image credits: Top, courtesy of Heather Buzzard; bottom, iStockphoto.com. 

The art of enriching lives hit by Alzheimer's

In the above video, Beth Galvin of Fox Atlanta news reports on a new program called “Museum Moments,” started by Emory medical student Emily Lu. The program uses art as a bridge to help people like Cecile Bazaz, who has early onset Alzheimer’s disease, reconnect with the world around her.

“I’m bored out of my mind,” says Bazaz, 53. Museum Moments gives Bazaz something special to look forward to, since her condition has forced her to give up a high-powered job and lose much of her independence.

Guides at Emory’s Michael C. Carlos Museum are specially trained to engage people who are suffering from memory loss by asking them questions, rather than just lecturing.

“It’s called Museum Moments because we hope we give you a moment to be yourself again, just be an individual looking at art, where there are no wrong answers,” Lu explains.

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Injury made normal river bacteria hazardous

How could something in Georgia's Little Tallapoosa River have made Aimee Copeland so sick? Atlanta's 11 Alive News took a water sample of the river to Emory's Center for Global Safe Water to test for Aeromonas Hydrophilia, the bacteria that gave the 24-year-old from Snellville necrotizing fasciitis, a vicious, flesh-eating infection. (See video, above.)

The Emory analysis showed that a tablespoon of the river water contains about 140 cells of aeromonas, which is not an unusual amount to find in any untreated lake or river water. Necrotizing fasciitis is a rare disease, and aeromonas bacteria normally do not pose a risk, unless you have a deep cut or traumatic wound.

"The water and the bacteria get forced into the really deep tissue and then it's difficult to get them back out when you clean," says Amy Kirby, a research assistant professor in Emory's Rollins School of Public Health.

Copeland remains in critical condition and faces multiple amputations, following an initial amputation of her left leg after a zip line broke and she fell into the river. Read more at 11alive.com.

The rare book that changed medicine

In 1543, Flemish physician Andreas Vesalius published “On the Workings of the Human Body,” or “de Humani corporis fabrica,” containing the first accurate representations of human anatomy.

Only 60 original copies remain of the seminal work, including one housed in Emory's Manuscript, Archives and Rare Book Library.

The book's publication was not just a monumental feat of science and art, it was an act of bravery, says Robert Gaynes, a professor in the Emory School of Medicine. Vesalius’ book debunked the preceding 1,200 years of anatomical knowledge, which were based on the work of Galen of Pergamon, a prominent Roman surgeon. “At that time, criticizing Galen was essentially heresy,” Gaynes says.

Vesalius was a surgeon and professor of anatomy who was the first to perform human dissections as a teaching tool, inviting his students to gather around the operating table and observe first-hand as he worked. “He began to have this disquieting feeling that many of the things that Galen said in his anatomical text were wrong,” Gaynes says. “He realized that Galen had never dissected a human and was inferring human anatomy from animal anatomy.”

Vesalius worked with a leading artist to produce the stunningly detailed and accurate drawings, some of which include Renaissance-style landscapes as background. The drawings were used to produce fine woodcuts, which were then printed on linen pages. The result is a work of science and art that survives more than 450 years later, and remains relevant.

The title page of the book shows Vesalius standing over a cadaver in an elaborate lecture hall, jam-packed with observers. You have to look closely to notice a dog in one corner of the drawing has a human foot for its left hind paw – a dig at Galen.

“Observation, and believing what you could see, was the watchword that Vesalius worked by, and it changed everything in medicine,” Gaynes says. “Medicine finally began to move forward because of this book.”

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