A visit to Cerro Pelon: monarch overwintering site
On December 7th, 2019, I traveled with family and friends to Cerro Pelon, a mountain in Mexico that is home to a large colony of overwintering monarch butterflies. Cerro Pelon is located inside The Monarch Butterfly Biosphere Reserve straddling the states of Michoacan and Mexico and encompasses 217 square miles. There are colonies throughout the reserve on different mountain tops including the famous “El Rosario.” Cerro Pelon is somewhat less frequented as the colony is smaller and the hike more difficult.
We drove the three hours from the capital of Michoacan, Morelia, to the Macheros Cerro Pelon site where we were greeted by a number of guides with horses. The hike this year was somewhere between 2.5 - 3 miles, but at 9,000 - 10,000 feet in elevation, we all ended up on horseback for most of the journey. The final half mile is too steep for the horses though, so do come prepared for a bit of serious hiking if you ever intend to visit yourself.
As a graduate student studying monarchs and their migration, I’ve seen my fair share of monarch butterflies. I rear them each summer and autumn for my research. I watch them fly over my home in Chicago at the beginning of their journey. I have seen them stop to nectar in Oklahoma and Texas before heading beyond the border into Mexico. I have even experienced their re-migration in the early spring - tattered butterflies in search of any available milkweed. So I wasn’t entirely sure how I would feel about seeing the only part of the journey I had yet to witness. The most sensational, but also the most well documented part of their year long journey.
Maybe unsurprisingly, the experience actually felt very personal. The migration, its evolution and maintenance, all things that I am working to understand, are on display in the thousands and thousands of monarchs resting in trees and circling overhead. Of course you don’t need to study migration, monarchs, or biology at all to be in complete awe. The experience is surreal - you can hear the flapping of thousands of butterflies while they fly past and above you in waves seemingly unending. You become aware that you are standing among nearly an entire population of animals in one small place - that they are only here. This congregation of a species is unbelievable and in the monarchs’ case, also very beautiful.
View of the forest on Cerro Pelon - a few hundred feet below the colony.
As we rode up the rocky trails, monarchs slowly began to appear until at one point they started streaming down the mountain headed for small puddles of water to hydrate - an activity known as “puddling.”
Monarchs circling above the colony - some leaving to re-hydrate and others returning to the trees.