By William Rapai
*The following story appeared in the Fall 2017 edition of Michigan Nature Magazine
Many flowers—especially native plants—are terrific sources of nectar for monarch butterflies. Photo by Wendy Caldwell, Monarch Joint Venture
It’s September at the Michigan Nature Association’s Goose Creek Grassland Sanctuary.
Even though asters and goldenrod are in bloom, most plants that grow here—including the three species of milkweed—are in decline.
Hanging from the underside of a leaf, a Monarch butterfly emerges from its chrysalis, with an urge to do only one thing: fly to Mexico.
Five generations of Monarchs have hatched already during this calendar year, but this individual is different. Always synchronized to the lifecycle of the milkweed, this Monarch inherently understands that fall is approaching and it must go.
Monarch butterflies are not able to survive the cold winters of most of the United States so they migrate south and west each fall to escape the cold weather. They travel much farther than all other tropical butterflies, up to 2,000 miles. They are the only butterflies to make such a long, two-way migration each year. Map courtesy U.S. Fish and Wildlife Service
There are no roadmaps or guideposts for the Monarch and there will be no adults that have made the journey before to show the way. There is only an inner drive that guides the butterfly on a 2,000-mile journey south and west, across the corn belt, the hot, dry plains of Oklahoma and Texas, across the Rio Grande, and over the mountains of Mexico to a place it has never been before—the Monarch Butterfly Biosphere Reserve west of Mexico City—where it will spend the winter in hibernation.
There are Monarchs all across the United States and the southern tier of Canada and biologists split them into two populations. The western population winters in southern California and spreads out across the west coast and the Great Basin in the summer. But the eastern population—those butterflies east of the Rocky Mountains—return to Mexico in the fall in one of the most astonishing natural phenomena on this planet. Other butterflies migrate—both north in the spring and south in the fall—but the Monarch’s journey is unique because of the distance and the entire population somehow finds its way to one location in the mountains of Mexico after being spread out across half of North America.
Reason for Alarm
This eastern migratory population is in jeopardy, however. The Monarch’s population is in trouble, caught in the crossfire of changing land use and habitat loss, drought in the southern plains, dangerous pesticides, and extreme storms. In the early 1990s, the eastern population of the Monarch was estimated at more than 500 million individuals. By 2014, that number had fallen to about 34 million. The population has rebounded somewhat since then—to an estimated 56 million in 2015, according to Chip Taylor, the director of Monarch Watch at the University of Kansas.
Even though the numbers have perked up, there is still much reason for concern. A 2016 study of this population by the Scripps Institution of Oceanography at the University of California at San Diego and the U.S. Geological Survey concluded that it could go extinct sometime in the next two decades. In fact, the eastern Monarch population decline has become such a concern that in 2014 President Barack Obama issued an executive order to create the National Pollinator Task Force to develop an action plan to save declining populations of honeybees and restore the eastern Monarchs to about 225 million.
The Monarch’s population crash has increased the importance of sanctuaries like the Goose Creek Grasslands. This 70-acre sanctuary is just a postage stamp on a landscape dominated by agriculture, but it has everything a Monarch needs: flowering plants that provide nectar and plentiful milkweed, which is the only food source for Monarch larvae. This place also has sanctuary manager Rachel Maranto and many generous volunteers who work hard to remove glossy buckthorn, an invasive plant that would grow property line-to-property line and quickly dominate the entire landscape if not controlled.
The on-the-ground work at the Goose Creek Grasslands is representative of the commitment the Michigan Nature Association has made to the Monarch. MNA has been working with the Michigan Department of Natural Resources and other government agencies, non-profits, and citizens to promote the health of the Monarch by promoting the planting of additional nectar plants and milkweeds.
Nectar gardens are particularly important for the Monarch’s fall migratory generation. Weight gained by those butterflies during migration will have to sustain them because they won’t eat anything until they come out of hibernation in March, says Cora Lund Preston, a communications specialist with the Monarch Joint Venture, a Minnesota-based partnership of more than 60 organizations.
There’s one more thing unique to this fall migratory generation: for their entire migration and hibernation, they are locked in a juvenile state called “diapause,” which makes them unable to breed. Always synchronized to the milkweed, they only become adults and breed after they emerge from hibernation in March as milkweed plants sprout in Mexico and Texas.
But all that is months ahead for this Monarch. It’s a sunny September day, and the Monarch is torn whether to leave Goose Creek. Michigan is a pretty good place for a Monarch in any generation, says Stephen Malcolm, a professor of chemical biology at Western Michigan University. The landscapes of states to the south and southwest—Ohio, Indiana, Illinois, and Iowa—are a vast monoculture of corn and soybeans that provide very little in the way of food or places to breed. Michigan’s less agriculturally intense and more complex environmental matrix is good for Monarchs because it provides more places for milkweed and nectar plants to grow. In addition, the moderating impact of the Great Lakes limits temperature extremes.
Monarch butterflies at MNA’s Fred Dye Nature Sanctuary in Mackinac County. Photo by Adrienne Bozic.
Despite those luxuries, migratory restlessness is too much to overcome and this Monarch lifts off from a goldenrod, to start a perilous journey. This trip would be dangerous for any animal let alone one that weighs only about a half a gram—a hundred times as heavy as a grain of sand. There are predators and the risk of being struck by a speeding vehicle or being caught in an early frost.
Near Impossible Challenge
Like other Monarchs traveling across the Midwest, this butterfly’s first challenge is finding food on a vast landscape of corn and soybeans. Often there are flowering plants growing along rural roads—New England aster, stiff goldenrod, black-eyed Susan—but there’s also danger here. If the plants are near an agricultural field there’s a chance they have been contaminated with neonicotinoids or some other insecticide.
Neonicotinoids are considered harmless to humans in small amounts, but to insects like butterflies and honeybees they are deadly. The pesticide is systemic, which means it reaches into all parts of the plant and kills any insect that comes in contact with any portion of the plant. Many of the corn and soybean seeds planted across the Midwest are treated with neonicotinoids, and the insecticide is absorbed as the plant germinates and grows. Other neonicotinoids are sprayed on plants or are included in irrigation water, which unfortunately allows them to spread to nearby non-agricultural plants. For a pollinator like a honeybee, even a minute amount is lethal.
For the Monarch, however, the impact of neonicontinoids will be fully felt when a new generation arrives back in the Midwest the following spring. A 2015 U.S. Department of Agriculture study showed that even if milkweeds are not treated directly, they can contain neonicotinoid compounds in levels high enough to be fatal to Monarch caterpillars if they grow near treated agriculture. (You may very well have a neonicotinoid compound in your house even if you pride yourself on not using pesticides on your garden. Have a dog or cat? If it wears a flea or tick collar, it likely has a neonicotinoid as an active ingredient.)
Mountains west of Mexico City are the winter refuge for most of the monarch butterflies in North America. Photo by Wendy Caldwell, Monarch Joint Venture.
As the Monarch approaches the Rio Grande, it and other migrating Monarchs from across the eastern United States funnel into a narrow corridor that parallels the Gulf of Mexico. There are two dangers here: drought and tropical storms. A four-year drought in this area earlier this decade took a severe toll, as Monarchs were unable to find food as they traveled through the area. In 2011 alone, 97% of Texas was in drought with 88% of the state experiencing severe drought.
After migrating from the United States and Canada, monarch butterflies spend the winter in oyamel firs at a few mountain forests in Mexico. Photo by Wendy Caldwell, Monarch Joint Venture.
That drought also had an impact for three straight springs: Monarchs emerging from hibernation in March went north expecting to find young milkweed plants growing so they could breed and lay eggs and for three straight years there were almost none. A wet spring in Texas in 2015 gave the migrants a bumper crop of milkweed, and the Monarch population responded accordingly.
And then there is the danger of running headlong into a tropical storm entering Texas or northern Mexico from the Gulf of Mexico. Biologists say it’s common for Monarchs to survive the heavy rains and high winds by burying themselves in leaf litter, hiding under rocks, or taking shelter in a hollow part of a tree.
Ten weeks after it left Goose Creek, this Monarch has made it safely to the Monarch Butterfly Biosphere Reserve in central Mexico. Technically this reserve is a tropical resort—only about 19 degrees north of the Equator—but at nearly two miles above sea level, the area has a unique microclimate and winter temperatures range between 32 and 60 degrees Fahrenheit. The butterflies cluster together on the branches of evergreen trees to keep warm.
But this clustering—the entire population in less than 50,000 acres—makes the Monarchs vulnerable. A storm in early March 2016 brought cold temperatures and high winds that knocked down about 133 acres of trees and killed an estimated 6.2 million butterflies.
A Cycle Worth Saving
In March, the sun climbs higher overhead, the thin mountain air begins to warm and millions of Monarchs emerge from hibernation and search for food. No longer in diapause, they now also search for mates and milkweed plants to lay their eggs and continue the butterfly’s lifecycle.
There will be as many as five generations during the year as the Monarch again spreads out across eastern North America, reaching Michigan and the Goose Creek Sanctuary in early May.
And on a late summer day, with the milkweed in decline at a sanctuary in southern Michigan, a Monarch will emerge from its chrysalis, with an urge to do only one thing.
A monarch butterfly rests on goldenrod before continuing toward its migration destination. Photo by Wendy Caldwell, Monarch Joint Venture.
William Rapai is the author of two Michigan Notable Books: The Kirtland’s Warbler (University of Michigan Press) and Lake Invaders (Wayne State University Press). He is also the president of Grosse Pointe Audubon and has a milkweed/pollinator garden in his front yard.