Seeing the Monarch Butterfly hibernation in the mountains two hours west of Mexico City had been on my bucket list since a co-worker told me about the awe-inspiring experience 18 years ago. So, when we decided to spend the winter in Mexico, visiting the Monarch Butterfly Biosphere Reserve was my number one priority.
We thought the timing would be perfect to head to the reserves after our month in San Pancho. But as we began our research two weeks into our stay there to plan our five week travels through Mexico, we learned two things: (1) the population of monarchs in central Mexico this winter was estimated to be the highest in since 2006-2007 (YAY!), and (2) due to unseasonably warm weather, the butterflies were more active than usual and an early northward migration was expected (OH NO!). I wasn’t about to miss the opportunity to see these gorgeous pollinators at a 13-year population high, so we made the spur of the moment decision to rent a car and make the 21-hour+ round trip drive to the mountains.
And it was so worth it. The experience was more amazing than I ever imagined and yet incredibly difficult to describe.
We arrived at El Rosario Sanctuary just after it opened, parked the car, and began climbing. Coming from sea level just the day before, the steep ascent at 10,000 feet in elevation was challenging. Luckily, the butterflies were concentrated lower on the mountain this year than in years past.
After a 10-minute hike, in which we saw our first red warblers of the trip, we began to see clusters of butterflies high up in the oyamel fir trees. As the sun rose and warmed the trees, a small confetti-like orange explosion erupted from the limbs.
We stood, rapt with smiles plastered on our awe-struck faces, as thousands and then millions of butterflies flew, fluttered, and floated through the air.
They swarmed the shrubby understory of the forest, landed on the hats, shoes and sometimes faces of the onlookers.
The quiet of the forest broken only by the sounds of their fluttering wings.
As the day warmed further, they drifted down the mountain seeking water sources, swarming the creek bed and any puddles they could find.
The migration of monarch butterflies is one of the most epic migrations of any creature on the planet. Each fall, as temperatures drop in the U.S. and Canada, monarch butterflies begin the journey south, some traveling as many as 3,000 miles to reach their overwintering grounds in Mexico and cluster by the millions in the branches of the oyemel fir trees. These forests, high in the mountains, create the perfect microclimate for the butterflies with a Goldilocks effect, not too hot and not too cold. Come spring, the butterflies begin mating and head north to the southern U.S. where they lay their eggs. In just a few days, the black, yellow and white striped caterpillars emerge, feeding voraciously (and solely) on milkweed before forming a chrysalis, from which a butterfly will emerge.
This new generation then migrates further north seeking a new patch of milkweed, where they will breed a new generation. This process is repeated up to five times before reaching their furthest northern habitat. These northern migrating butterflies complete their life cycle in just five to seven weeks each. However, a “super generation” that can live for up to eight months, then makes the migration south to the overwintering grounds in Mexico, returning year after year to the same forests that their great-great-great-great grandparents left the previous spring.
Although the population was cause for celebration this year, the population trend for monarchs overall is decreasing due to the effects of logging, herbicide use and climate change. It is estimated that overwintering monarchs once numbered close to 1 billion. Now the population is closer to 100 million, a 90% decrease. The fir forests in Mexico as expected to all but disappear by the year 2090 as a result of climate change. Thus, local residents are taking somewhat controversial steps to plant oyemel trees at higher elevations than they currently grow.
If you want to help increase the monarch population and you live in the U.S., planting milkweed in your garden will help the population thrive as it makes it northerly migration each year.
And if you want to see this spectacle for yourself – and trust me, you do – plan a trip to central Mexico in February. You won’t be disappointed!
We capped our whirlwind trip with a day of birding in the forests above the town of Zitacuaro, our home base for exploration. We walked from our Air Bnb to the end of the road and then on a trail up the mountain. As we got to the forest, and the end of town, we noticed at first a few, then dozens, then hundreds of monarchs fluttering through the sky, apparently from a nearby roosting site (not within an official reserve). As we hiked up the trail, we marveled once again at these delicate creatures, while also exclaiming over sightings of slate-throated redstarts, and crescent-chested warblers. It may have been a short trip, but it was one that is indelibly etched in my memory.