Deciding which places to visit and which to skip is one of the hardest things about traveling for an extended period of time. You will undoubtedly have less time than you plan for and you simply cannot see everything. While much of our trip is spontaneous, deciding one night where we hope to end up the next, we also have a mental list of “must-sees” along the way. For me, witnessing the Monarch butterfly migration in Mexico, one of the most impressive migrations in the animal kingdom, was on the top of this list.
Every August millions of monarch butterflies begin a 4,000 km migration from the Great Lakes region of the US and Canada and congregate in a geographically small area in southwestern Mexico. They spend the winter waiting out the freezing temperatures in the north. In the spring, when they’ve reached sexual maturity, they mate and the pregnant females begin the migration north to Texas, Florida or other southeastern states to lay their eggs in milkweed bushes. The new generation of Monarchs emerge in late May and finish the migration further north back to the Great Lakes region. By the end of the summer in the north, yet another generation of Monarchs prepare for the long trip south to Mexico. No single Monarch makes the entire journey in a lifetime; rather, it takes 3-5 generations to complete the trip. As if this weren’t impressive enough, what really amazes me is that the butterflies return to the SAME trees, year after year, despite the fact that they aren’t the same butterflies that made the trip the year prior.
Mexico has twelve separate butterfly “sanctuaries”, areas of land that have been decreed ecologically important enough to merit a protected status (Reserva de la Biosfera). Despite the protected status, illegal logging is a big problem on these lands and it is estimated that up to 60% of the reserve lands have been severely damaged. To protect the fragile migration, not all sanctuaries are open to the public. After seeing how many people visit the sanctuaries on any given day, this is probably a good thing. There are plenty of viewing areas that are open to the public, two of which we visited on our drive from Guanajuato to Mexico City.
When the temperature is cold, the butterflies cluster together in huge clumps, covering whole fir trees and literally weighing down the branches. This was the state of the butterflies on the days we visited. Each time the sun shone through the clouds, the butterflies fluttered around in all directions, many landing on the warmed branches to soak up the rays. When the sun once again retreated behind the clouds they too returned to the warmth of their huddles. I have heard that on really hot days, thousands of butterflies will descend to the humid forest floor during the hottest part of the day and cover the ground completely like a brilliant orange carpet.