The Mighty Monarch Butterfly Sets Out on Long Migration
Every autumn, thousands of monarch butterflies gather at Point Pelee National Park in Ontario before embarking on one of nature’s most astounding journeys—an over 1,800 mile trip to central Mexico.
The tip of the Pelee peninsula, Canada’s southern-most landmass, acts as a jumping-off point for the butterflies, providing a shorter way across Lake Erie as they head south.
“They come from further north, and Point Pelee is a stopping ground on their way,” says Meaghan Ruston, Point Pelee National Park’s promotions officer.
Although monarchs have been undertaking this monumental journey for thousands of years, it was only in the mid-1970s that researchers discovered they were overwintering in the volcanic mountain ranges of central Mexico.
That such a small insect can travel so far is considered a scientific wonder. Even more remarkable is that the monarchs that migrate to Mexico for their winter hibernation have never been there before.
But the survival of this marvel of nature is in jeopardy, so much so that Canada, the United States, and Mexico agreed in 2007 to work together to protect the monarch’s habitat.
As a result, the North American Monarch Conservation Plan (NAMCP) was drawn up and implemented to address some of the threats to the monarchs—threats that include pesticides, climate change, and illegal logging in Mexico’s oyamel fir forest, a unique mountain habitat where they spend the winter.
Karen Oberhauser, NAMCP principle author and an associate professor at the University of Minnesota, says that because monarchs in Canada and the United States depend upon a vast range of habitats that lie outside national parks or government land, “education is really important.”
“A lot of it is outreach—trying to encourage people to either preserve habitat or create habitat for monarchs,” she says.
This includes encouraging farmers to grow plants on the edges of their fields that support monarch populations and have city dwellers plant monarch-friendly gardens or natural areas in their yards.
Herbicides that kill milkweed—the only plant that monarch caterpillars eat, are also a problem for the butterflies.
The all-important milkweed, Oberhauser said, is “one of the big conservation efforts that we’re working on right now.”
“We’re working really hard to make milkweed seeds that are appropriate for each region in the breeding and migrating range available. So depending on where people are in Canada and the United States, we’re trying to make locally appropriate seed sources available to people.”
The situation is different in Mexico, where the monarch’s overwintering site is protected by the government. The forests, which provide the perfect micro-climate for the monarchs, have also been designated a UNESCO heritage site. However, illegal logging continues to be a problem.
But while the number of monarchs at the overwintering site were the lowest on record in 2009—attributed mainly to weather extremes, especially high spring temperatures in Texas where the insects stop on their return trip—the numbers this year so far look about average, says Oberhauser.
“In the upper mid-Western United States and Ontario, so kind of the center of the continent, which is the important breeding range for monarchs, the weather was just ideal. We had plenty of rain so the milkweed was in really good condition.”
After the overwintering generation mates in the spring, their short-lived offspring, with only four or five weeks to live, continue making the trek northward over several generations.
Last year, biologists determined that, along with a compass in their brains, monarchs have a molecular clock in their antennae that helps them navigate and keep flying in the right direction.
To conserve their energy on the trip, the insects drink nectar and catch warm air currents that allow them to soar instead of using powered flight as they go.
By the time the monarchs reach Mexico they’re in the millions, crowding onto the branches of the oyamel trees where they remain in a comfortable torpor until the urge to reproduce rouses them the following spring.
Oberhauser, who began studying monarchs in 1984, is a board member with the Monarch Butterfly Fund (MBF). Through a program called Journey North, MBF tracks the monarchs each fall and spring as they travel to and from Mexico.
The organization is also working to raise money to protect the monarch’s overwintering sites in Mexico.
“If we provide them the habitat that they need, they have this capacity to rebound,” says Oberhauser. “They’re pretty resilient. We need to do what we can to protect them, but if we do protect them they’ll be able to use what we give them.”
In Canada, the largest populations of the bright orange and black insects are found in Ontario and Quebec. The monarchs that migrate south each fall are the unique “Methuselah generation”—long-lived butterflies that can make it all the way to Mexico and back as far as the Southern United States before having to reproduce.
At Pelee, park staff, along with visitors, and amateur lepidopterists, carry out an official count of the butterflies in order to monitor their numbers. Their roosting sites are tracked as they make their way through the United States as well.