On the path of Latin America's greatest wildlife migration

‘I gazed in amazement at the sight’ reads a photocopy of a 1976 National Geographic article on my lap. The words are bouncing on the page as the truck flies over steep mountain roads, but I can’t stop reading. ‘Butterflies — millions upon millions of monarch butterflies!’

The monarch’s wintering home — a mystery to scientists until the 1970s — was confirmed when Canadian zoologist Fred Urquhart and American entomologist Lincoln Brower were called to the northern Michoácan mountains in early 1976. Urquhart had spent 30 years studying their winter migration and the discovery made the cover of National Geographic a few months later, with a feature written by him. 

Almost 50 years on, I’m making the same journey to Mexico’s Central Highlands, hoping to see the world’s greatest insect migration for myself. These days it’s possible to take a tour. I’ve joined a five-day trip to El Rosario and Sierra Chincua, two UNESCO-protected sanctuaries in the Highlands. Between November and March, they become the wintering grounds for millions of monarch butterflies seeking refuge from the freezing temperatures in North America. 

Our open-air truck rattles on a cobbled road as we climb to 9,850 feet above sea level. Now and again I get a glimpse of the mighty Sierra Madre: a chain of densely forested mountains cloaked in wisps of pearl-coloured fog, or perhaps smoke from a village cooking fire.

Cowboys ride the cobbled streets on horseback, trailed by dogs that look like polar bears. At El Rosario, we mount horses to help us reach the monarch colony. When the steep, muddy trail opens into a clearing, we dismount and continue on foot. Raindrops hang from pine needles like icicles and I see a flash of green and red as a white-eared hummingbird sips on nectar.  

With every step, the number of dead or drowsy butterflies resting on the forest floor multiplies. Their wings, thin as parchment paper, are a deep orange with black veins and white spots along the edges. “We’re getting close,” whispers one of our guides, Eric Ramirez. 

Up ahead, I spot enormous native oyamel fir trees covered in a strange textured shadow that runs along the trees’ midriffs, like an embroidered dress woven in grey and pale orange threads; their branches droop and sway with great effort in the wind. “We’re here,” says Eric, excitement ringing in his voice. 

It takes me a moment to realise but, just as Urquhart had described, thousands of monarchs are clinging to the trees in thick clumps with wings closed tight, like a beehive protecting its queen. While a single monarch weighs less than a gram, their combined weight is heavy enough to warp the branches of an ancient oyamel tree. Despite never visiting this forest before — it takes at least four or five generations of monarchs to complete the round-trip from North America to central Mexico — the butterflies return to the same group of fir trees every year, huddling in ‘roosts’, to minimise predation.

“It’s a mystery how they know where to go,” Eric tells me as we take a closer look through a telescope. “Brower had a theory that they use magnetite crystals in the earth to navigate, but we don’t know for certain.”

The next morning, 11 miles north in the butterfly sanctuary of Sierra Chincua, the sun pierces through the clouds, warming the monarchs’ wings and sending them fluttering into the air. Their deep orange sets the blue sky ablaze, as if someone has lit a million pieces of paper on fire and dropped them from a plane.

Surrounded, I’m sure I can hear their wings beating through the air, like a whisper in my ear.“If you’re quiet enough, you can hear them talking,” says a man next to me. He’s a mezcal producer from the nearby city of Zitacuaro, visiting with his family. I ask who he means by ‘them’. “Our ancestors,” he responds. 

Monarchs often arrive in Mexico around Dia de los Muertos (Day of the Dead; 1 -2 November), a time when Mexicans believe the departed can rejoin their families for feasting and celebration. The timing led the Purépecha — an Indigenous group that settled in Michoacán around the 11th century — to believe monarchs were the souls of their ancestors returning to Earth. 

“You think this is beautiful,” says Diego Gonzalez, our guide in Sierra Chincua, as the butterflies flutter back to their branches. “I remember when we had 400 trees full of monarchs — you couldn’t see the sky there were so many.”

It’s difficult to believe while I’m surrounded by thousands of them, but monarch butterflies are at their lowest-ever numbers. According to WWF, their population has declined by 90% in the last two decades due to illegal logging in Mexico, the use of herbicides in the US and Canada, and extreme weather conditions caused by global warming.

Conservation organisations such as WWF and the Monarch Butterfly Fund are working with land owners and governments to reduce deforestation and protect the monarchs’ wintering grounds. Sustainable wildlife tourism — the most obvious alternative to logging — could be part of the solution. 

“We know monarch populations can bounce back quickly given the chance,” says Fernando Romo, who’s been guiding monarch tours like this one for Natural Habitat Adventures, WWF’s official tourism partner, in Michoacán, for over 20 years. “I’ve noticed big changes in the town of Angangueo — more children are going to school, houses are in better condition, and there’s very little illegal logging within the sanctuaries now. That’s all down to tourism.”

Whether the only known butterfly migration on Earth will still exist in another 50 years is uncertain. But, for now, Mexico’s conservation efforts and the commitment of local communities gives me some hope for the monarchs’ survival.