In the winter of 1974, in the high mountains west of Mexico City, Ken and Cathy Brugge found a few dead monarch butterflies lying tattered by the side of the road. It was exactly what they had been searching for, and sure enough, with a little exploration of the forests in the vicinity they uncovered the answer to one of entomology's great unanswered questions- where did all the eastern monarchs go in winter? The monarch is a common butterfly in North America, but come winter they simply vanished with no apparent trace. No eggs, larvae or pupae were ever found during those months.
It was known that thousands of adults gathered in the Monterey pines on the west coast. But they were the ones from the west of the rocky mountains. What happened to the vast majority of the monarchs- the ones from east of the mountains- was unknown. It was assumed that they migrated south to sunnier climes. But where, exactly?
Monarch country....
The answer, evidently, was that they went to these forests. Every monarch in the eastern part of North America. That's millions upon millions of butterflies converging on a series of small woodland glades where geographical and climatic factors rendered the temperature, humidity and protection perfect for overwintering.
The monarch is one of the most recognisable butterflies in the world. It's America's national insect. And it's a superhero amongst butterflies. It can live for over 9 months including hibernation, and a single individual is capable of travelling thousands of miles. The occasional Monarch even shows up in Britain, having been blown across the Atlantic ocean. Monarchs die harder than Bruce Willis.
Monarch larva (full grown)
During summer, they spread out from the Mexican mountain forests across the whole of North America, taking several generations to do so. The large larvae feed exclusively on Milkweed (asclepias sp.) and absorb the poison from the foodplant- hence their warning colouration. Birds do not mess with the monarch.
Then, just as they've covered the continent, they all turn around and several generations later, arrive back in Mexico ready for hibernation.
Which is where I found them in February 2001. As I huffed and puffed my way up the mountain, the sun was out and by mid morning it was perfect weather for an overwintering butterfly to wake up, give its wings a stretch and head out on a brief sortie to find food and water. In a few weeks, it would be time for them to move on, but for now they were just preparing for their epic and neverending journey.
As I got nearer to the colony, I started to see them. First in the sky, and then on closer examination, drinking from the tiny streams that criss-crossed their way down the mountainside.
A sky full of monarchs
Drinking at a stream
There had been a frost the night before and, as I turned a corner on the narrow trail, I had my first taste of the true extent of the monarch migration.
Logging had encroached into the surrounding forest, and one theory goes that the damage done by the loss of the trees protection had started to affect the overwintering butterflies, so that a few on the outskirts of the colony had started to feel the cold. The trail ahead of me was liberally carpeted with dead and dying butterflies, suffering from exposure.
There were so many that I wondered how the colony could possibly survive the loss of such numbers without being severely depleted. But then, a little further on, the incredible truth started to dawn...
Dead monarch carpet
It's the sound that first lets you know that you're in the kingdom of the monarch. It's a sound so unfamiliar to our ears that it took me a while to understand what it was. It's kind of like the sea breaking on the shore, but it's constant- it doesn't swell and then recede like that sound. It's a whisper, but it's loud enough to overshadow everything.
It's the sound of a million million wings rubbing together all at once. And when you realise what it is, you stop dead in your tracks. I have never heard anything like it, and don't really expect to again.
Now and then, you'll hear a sharp crack, as a branch gives way under the weight of butterflies that it carries. Think about that. A pine tree branch, snapped by weight of butterflies! Surely it would take a stupendous number of insects to pull off a feat like that?
And that's when you start to notice the trees. I mean, really notice them. Notice the bunches of grapes hanging from them. And then, a flash of orange tells you that they aren't grapes at all. In some cases, they aren't really trees at all. They're more like butterfly sculptures of trees. And you're standing right in the middle of one of the biggest migrations on the planet
Bunches of grapes...
Not just trees...
Butterfly sculptures
Everywhere you look, there are butterflies. You think you're seeing a tree, you're actually seeing butterflies. That's not a bush- it's a group of 10,000 butterflies. They're everywhere. And as the sun warms their wings, they rustle them gently and open and close them so that it looks like a thousand tiny pops of orange, exploding all over your vision.
Not a bush...
The sun moves higher, they start to disperse and fly afield in search of nourishment, and the clearings are filled with swirling orange confetti. It's a butterfly snowstorm.
After a couple of hours with the monarchs, I made my way down the mountain. I was still not adjusted to the altitude, so I hitched a ride on a mule. I was pleased about that, but I can't say that the mule was too keen. I think the camera gear may have been to blame. Heavy things, Nikons. Certainly, it couldn't have been anything to do with my weight. That's my story and I'm sticking to it.
I travelled with Tim Melling and Naturetrek, and it was one of the greatest experiences of my, and I suspect anybody's, life. It took two days for my grin to subside. If I could design a perfect trip, it would be to the sea of Cortez to photograph whales, and then on to mainland Mexico to visit the monarchs. Two weeks of pure natural history wonderment. Brilliant.
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