Monarch butterfly at El Rosario.
The Great Monarch Migration
Monarch butterfly at El Rosario.
It’s warm under the big stack of blankets, but the air in our room is crisp and cool. Like many buildings in the small mountain town of Angangueo, our hotel has no heating. The evening before we sat in our room wearing sweaters and jackets and drinking plenty of hot tea to ward off the mid-January chill. Now we have to get up so that we can head even higher into the mountains, to about 10,000 feet or close to 3,000 metres, where it’s even colder. But once we remember where we are, thoughts of cold are quickly replaced with anticipation of what awaits. We’ve come to see one of nature’s most unusual and awesome displays.
Monarch butterflies in North America have two important over-wintering sites. Those west of the Rocky Mountains head to the California coast, while those east of the Rockies – spread over an enormous chunk of Canada and the United States – head to a relatively small area of forested mountain tops in the Mexican state of Michoacán, west of Mexico City. The butterflies have been coming here every winter for who knows how long. Surprisingly, it wasn’t until 1975 that researchers finally discovered the long unanswered mystery of where the monarchs go. Local people around Angangueo always knew they were here, but when you have always lived with butterflies, why would you think that this is anything unusual? They’re not taken for granted anymore. Today, the Monarch Butterfly Biosphere Reserve is a UNESCO World Heritage Site.
The monarchs arrive in late November and early December and stay until sometime in March. Their numbers vary; in a good year it can be in the hundreds of millions. This area offers protection in a forest canopy of primarily oyamel fir trees, nearby sources of water, and a cool climate where they can preserve their energy. Unfortunately, their choice of a place that is often just above freezing puts them in a delicate balance, and every once in a while Mother Nature throws them for a loop. Frost is bad news and the occasional snowstorm can be disastrous. During the unusually harsh winter of 2002, over half the population died.
Our journey starts with a three-hour bus ride from Mexico City to the city of Zitácuaro, where we transfer to a local bus that winds slowly up the mountains, past corn fields and villages for another hour to Angangueo. The entire contingent of guests staying at our hotel – a family of five from Mexico City, a woman from Germany, and us – gets together to hire a van and driver to take us up to El Rosario, one of the most accessible of the nearby monarch reserves. Finding someone to take us is easy. In fact, they find us. New faces in town are easy to spot, and we seldom walk more than a block down the narrow cobblestone streets without someone stopping to ask if we want to see the “mariposas”.
The four-wheel drive van crawls slowly up the rough gravel road, along a series of switchbacks taking us ever higher with sweeping views of the valley far below. At the entrance to the reserve a local guide leads us on a footpath to a semi-open area in the forest where the butterflies hang out – literally hang out. At first it’s difficult to realize what we are looking at; it seems that many of the trees have trunks and branches twice their normal thickness.
“It's all butterflies,” whispers our guide in Spanish.
Normally a bold orange, monarchs are a more muted brownish gold when roosting with their wings folded. We’re looking at layer upon layer of butterflies clinging to trees. We came early in the morning because, in theory, we would see this phenomenon while it is still cool, then as the sun warms the air, the butterflies would emerge from the trees and we would see them fly off to feed and water.
But Mother Nature throws us for a loop as well. It’s one of those mornings that weather forecasters like to call a mix of sun and cloud. The sun never stays out for more than three or four minutes before another cloud comes by. The brief warmth stirs a few monarchs off the branches and into the sky, but then a cloud immediately brings them back to roost. The temperature is apparently right on the borderline between what they consider warm or cold. It stays like that for the next couple hours, never warming enough for many butterflies to leave the security of the branches.
By the time we arrive back in town, the mix of sun and cloud turns to pounding rain. We decide to stay another day, in hopes that the weather will improve. Walking around town in the evening after the rain storm ends, we meet Diego, another of the many locals who offer transport to the reserves. We talk about another reserve, Sierra Chincua, which is slightly farther away from Angangueo, and arrange for an early morning pick-up, assuming the weather cooperates.
The following morning is crisp but clear as we head up into the hills of Sierra Chincua. At the entrance to the reserve at the end of the road, we have the choice of either walking or hiring horses to reach the viewing area. Since it is uphill at an altitude near 10,000 feet, we allow ourselves the luxury of riding up the dusty path.
Leaving the horses, our guide Arturo leads us along the heavily forested path to a ridge that slopes into the valley below. Before long we come to a clump of trees thick with butterflies; many are already flying around as the mid-morning sun warms the forest. We stare at the spectacular sight, content to just stay there and watch, but Arturo assures us that just a little farther on, it gets even better. By this time we shed jackets and sweaters as it feels more like a summer than a January day.
The monarchs react to the warmth as well. Soon the semi-dormant butterflies come to life and take to the air by the thousands, then tens of thousands, perhaps hundreds of thousands; there’s so many it’s hard to tell. Bold splashes of orange speckle the blue sky as countless monarch butterflies fill the air and land on branches, logs, the ground, even on our heads and shoulders. We move slowly and carefully so as not to step on any. The sound is unlike anything we have heard before – a gentle, whispering-like whir, like a million pieces of confetti thrown in the air. Awestruck visitors speak in hushed tones as we witness the breathtaking spectacle.
Arturo talks in Spanish about the monarch migration, and shows us an easy way to tell males from females – males have a couple of extra black spots on their wings.
This migration is unique. No other butterfly in the world migrates this far and in such great numbers. The distance they travel from some parts of Canada can be as much as 5,000 kilometres. Their travels have been likened to bird migrations, but with a twist. Individual butterflies make the one-way journey only once, and many don’t survive the long trip. No monarch lives long enough to make a round trip, so no single butterfly can “remember” the route. The ones that make the return journey the following year might be the grandkids or even the great grandkids of this year’s migrants. Exactly how they find their way is still a mystery.
Threats to monarchs come from many fronts, the most obvious being shrinking habitat and deforestation. Key parts of the forest have been set aside as wildlife reserves, but there is constant pressure from logging interests and even illegal logging. In remote sectors of some reserves, armed rangers patrol looking for illegal loggers. On a positive note, the increased attention to the monarchs has helped the local economy, long dependent on mining and subsistence farming. Most tourist services, from guides in the reserves, to people providing transport, food, and lodging are run by locals. They have seen how the monarchs have contributed to their livelihood, and have become some of the strongest voices for conservation.
Altering habitats in Canada and the United States are also having an effect. Monarchs are picky eaters – the caterpillars dine exclusively on milkweed which contains chemicals that are poisonous to most birds. A bird that decides to eat a monarch soon regrets its menu selection. The bright orange colour has developed as a way of warning birds, “Eat me and you’ll be sorry!” But milkweed is often in short supply, and one cause that scientists point to is the increasing use of genetically modified crops that are herbicide resistant. Spraying a field to kill everything but the crop may be an efficient way of controlling weeds, but this also means less food for butterflies. The wild card in the longer term may be global warming which could alter the time of year that milkweed and other plants flower, adding to the many challenges that monarchs already face.
We leave with a feeling of exhilaration from seeing one of the great marvels of nature. But that feeling is tempered with the realization that this is a marvel teetering on the edge.
Monarch butterflies at their overwintering site near Angangueo, Mexico.
Monarch butterflies take flight at their overwintering site near Angangueo, Mexico.