Every autumn, the Monarch Butterfly migration takes place with millions of butterflies traveling over 3,000 miles from northeastern North America to spend the winter in the forests of southwestern Mexico. There are four preserves about two hours outside Mexico City, where visitors can see the butterflies high up in the mountain.
Experiencing the migration of the Monarch Butterflies near Mexico City is something out of a dream and one of the most extraordinary natural phenomena in the world. It’s mind-bending when you ponder how Monarchs manage to travel so far without a “map” to end up in the same place year after year in a tiny area in the mountains of central Mexico where these specific butterflies have never been. It’s a question for the universe.
El Rosario Monarch Butterfly Preserve
I’d paid a guide to drive me to one of the reserves in the mountains. The entire drive was peppered with traffic and concrete, garage-like housing. Despite driving two hours outside of Mexico City, it didn’t seem like we’d ever be in the wild. Eventually, though, the population became noticeably less dense. It wasn’t until the last 20 minutes that we were finally in the woods.
Why the Monarch Butterly Migrates
Monarch butterflies migrate because they can’t survive long, cold northern winters. Typically, these butterflies only live for about six weeks, but the migration takes months. So how do they do it?
It cannot easily be measured, and the butterflies aren’t telling. However, it’s believed that decreasing day length and temperatures, aging milkweed and fewer nectar sources trigger a change in monarchs; this change signifies the beginning of the migratory generation – a super butterfly able to make the trip.
Unlike summer butterflies, the migratory super generation can fly longer and live for nine months. The butterflies in the Monarch butterfly migration will not reproduce immediately, instead saving their energy and migrating south in search of the overwintering grounds where they have never been before.
Where to see Monarch Butterflies near Mexico City
The trail was a steep and steady incline and being at an elevation over 8,000 feet to which I was not accustomed, I had to stop frequently to catch my breath. It cost 300 pesos to take the horse and, in hindsight, it’s a bargain.
How Monarch Butterflies Find the Oyamel Fir Forest
When they arrive in Mexico, the butterflies in the Monarch butterfly migration huddle together on the Oyamel fir trees on southwest-facing mountain slopes. These locations provide cool temperatures, water, and adequate shelter.
Each migration is completed by a new generation of butterflies, so they cannot learn from others. Instead, they rely on their genes. Some scientists believe the butterflies of the Monarch butterfly migration have antennae that act as a genetic clock that tells them when to migrate. Knowing when to migrate and being able to find the way to a forest when you’ve never been there is an entirely different skill set.
Scientists believe the most likely explanation is that these butterflies, like our ancient ancestors, use celestial cues like the sun, moon, or stars and the earth’s magnetic field to find their way. They have an uncanny ability to navigate by measuring the sun’s position on the horizon with their eyes.
The Hike to See the Monarch Butterfly Overwintering Grounds
We sat on big rocks in the cool mountain air and watched as a couple of Monarch butterflies would flit past every few minutes. The higher we climbed, the more butterflies appeared. At first, it was just one or two, then six or eight, then dozens.
Finally, we made it to a horse trail and a steep climb up the last 300 yards.
Monarch Butterflies near Mexico City
Now, there were hundreds, maybe thousands of Monarch butterflies flying around. “Wow,” I said. “Wow.” Like some kind of deranged parrot.
Slowly, we climbed up the hill; there were a few other hikers now too struggling up the last leg.
The higher I climbed, the more butterflies there were. Thousands of orange and black Monarchs flitted about in the sky and swooped down low. I laughed out loud. These butterflies from the Monarch Buttery Migration flew up to 100 miles per day for 3,000 miles to end up here. I know many humans who wouldn’t be able to do that. These tiny, beautiful creatures are nothing short of miraculous. It’s hard to believe there are so many Monarch Butterflies near Mexico City.
When Butterflies Arrive in Mexico
It was the beginning of November and the butterflies were arriving in droves. At the top, there were about 10 other hikers and millions of butterflies at the top. Actual millions. They filled the air so densely when you looked up; they were nearly all you could see. The branches were heavy with thick orange and black clusters of them. Then, as I made my way to the end of the trail (It was roped off with caution tape and guards stood to watch), I saw the tops of the branches were utterly orange covered in millions of butterflies. Each tree was blanketed in tens of thousands of ‘roosting’ butterflies.
The swarms of butterflies were so massive that their wings made a buzzing sound that filled the air, like the soft sound of falling rain. We stood, jaws hinged open, in awe. We didn’t need to speak the same language to understand our collective experience.
These butterflies journeyed from Canada’s forests to Mexico to preserve their species. When spring arrives, these monarchs will reproduce, and their offspring will journey back to North America, always seeking the specific climate they prefer back “home” to a place they have never been.
Despite speculation, how they find their way back and forth remains a mystery.
Help Protect Monarch Butterflies
Millions of Monarch butterflies migrate each year, but their numbers are declining at a worrying rate due to climate change and loss of habitat.
Oyamel Firs are mandatory to preserve the Monarch species, but they are confined to high mountain areas that are few and far between. The monarch overwintering sites are found on only 12 isolated mountaintops along Mexico’s “Transvolcanic Belt.” However, the Oyamel forest ecosystem is Mexico’s most endangered forest type. Under threat from illegal forest harvesting and illegal avocado farms, only 2% of the original forest remains.
To protect them, the El Rosario Monarch Butterfly Reserve in Mexico was designated a UNESCO World Heritage site, but the threat is pervasive and encroaching.
You can do your part to help the Monarch butterflies by preserving their habitats by planting native milkweeds and stopping using garden pesticides that kill these insects and the nectar they need to survive.
See what else you can do, and find specific plants at Save the Monarchs.
Read other stories about Mexico here.
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