Winged wonders ... a monarch at the Biosphere Reserve.Credit: Reuters
Sara Evans witnesses the mass movement of monarch butterflies at their annual winter mountain retreat.
AS GOLDEN sunlight filters through the trees, slumbering butterflies begin to wake. Amber wings unfold and lift delicate bodies into the warm Mexican air.
Gentle as wood smoke rising, butterfly after butterfly leaves the safety of oaks and fir trees until the sky fills with millions of them. Moving closer to the sun, their wings - a deep orange filigreed with bold black markings - look like vast stained-glass windows and block out the blue of the sky.
As the sheets of butterflies dip and soar, the sound of a million insect wings in motion rumbles like a distant waterfall.
These are just some of the 250 million or so monarch butterflies that spend winter in the Sierra Madra mountains in the highlands of central Mexico. Every November, this particular patch of mountainside forest in Michoacan State, 240 kilometres west of Mexico City, becomes a temporary retreat for monarchs escaping the colder, faraway climes of eastern Canada and the US.
Their journey here is nothing short of fabulous. Fluttering, dipping and soaring for about 5000 kilometres at about 12km/h, the butterflies span a continent - passing over the Great Lakes, prairies, deserts, mountain ranges, cities and motorways to get here. Surviving storms and burning sunshine, these fragile creatures are the tissue-winged stars of what is one of the world's most dazzling migration spectacles.
Our journey here has been less epic. On horseback, it has taken half an hour or so to reach the butterflies. At 3650 metres, their roosting site lines a steep, tree-filled gully. We pause by the side of it to get a closer view. There are butterflies everywhere. From trunk bottom to the highest branch, the trees are coated in them. Boughs bend under their weight and sway softly in the breeze. The purple petals of wild lupines turn orange as butterflies smother them in search of nectar. Around water pools on the ground, huge clusters of thirsty monarchs make a fluttering carpet of wings as they drink.
Fed and watered, they sky dance. Tangerine bright, they fly through the gully riding the thermals, flitting between branches and sunbeams. Moving through dappled sunlight in their millions, the monarchs cast a nectar-fuelled spell that turns the forest into a bedazzling butterfly kingdom.
The Aztecs once believed that monarchs were the souls of warrior ancestors migrating through the forests on their way to the land of the dead. For centuries, people have welcomed the arrival of the butterflies in early winter, holding special celebrations in their honour. But it was only in the '70s that scientists discovered it was to this remote mountainside that the monarchs leaving North America were headed each autumn. Later research also revealed that the monarchs arriving back in North America in March are not the ones that spend winter here.
On the way, generations of monarchs mate, hatch and die. The ones that reach the US and Canada are fourth-generation - the great-grandchildren of those that left Mexico. These fourth-generation monarchs then fly back to Mexico in one go - somehow finding their way here and tripling their lifespan as they do so.
How and why this happens remains a mystery. What is known, though, is that this unique migration is not invincible. While the monarch itself is not endangered (populations thrive elsewhere around the world), this migration route is. Much of this is down to deforestation. Quite simply, as trees tumble, so do the number of monarchs. Without the warmth and protection of the trees, butterflies that have flown thousands of miles to avoid the ravages of northern winters, find themselves folding cold wings over their tiny bodies. They freeze to death overnight.
This is why this pocket of forest was given UNESCO World Heritage status in 2008. Logging is banned and the butterflies are officially protected. Comprising more than 56,000 hectares, the reserve - known as the Monarch Butterfly Biosphere Reserve - is divided into five main areas, four of which are open to visitors.
I'm in the newest reserve area, El Capulin, which is the least visited of the four and the least affected by illegal logging. The forest here thrives. Fir trees in their thousands stand tall and solid against a bright sky. Stretching out their evergreen branches to the millions of butterflies that flutter around them, these trees are butterfly guardians, keeping the monarchs warm and safe until they fly north on the start of one of the world's most complex and beautiful migrations, a journey that continues to mystify scientists and bewitch those of us fortunate enough to witness it.
Trip notes
Getting there
Delta flies from Sydney to Mexico City via Los Angeles and Atlanta, priced from $2000. 1800 144 917, delta.com. Leading car-hire companies are at the airport. El Rosario is the main sanctuary, in Ocampo, Michoacan State, 30 kilometres from Zitacuaro and 217 kilometres from Mexico City. Buses leave from Terminal Poniente (western bus station) in Mexico City to Zitacuaro several times a day. In Zitacuaro, there are buses to Ocampo and Angangueo, from where you can get to the sanctuaries.
When to go
The monarchs start to arrive at the Biosphere Reserve areas in November and leave in March. The best time to visit is in February, when the butterflies are at their most active in the early spring sunshine.
Touring there
A 10-day Mexico Monarch Butterfly Trail tour, departing December 30, is priced from $1119 a person, twin share. Tour begins and ends in Mexico City. 1300 796 618, www.gapadventures.com.
It is also possible to visit the four Monarch Butterfly Biosphere Reserve areas independently. They are accessible to visitors from November-March but exact opening dates depend on when the butterflies arrive and on the weather. The four reserve areas, El Rosario, Cerro Prieto, El Capulin (the least busy) and La Mesa each charge admission of about $2.50. Hire of a guide (which is compulsory) costs about $8, as does the hire of a horse (no riding experience is necessary because horses are led). It is possible to walk or hike up to see the butterflies; paths are well defined but the hour-long journey can be arduous and is at altitude, so a moderate level of fitness is required. El Rosario sanctuary receives 90 per cent of the 100,000 tourists who visit the Monarch Butterfly region.
Further information
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