As I’m sitting down to write this, millions and millions of monarchs are congregated in the oyamel forests on several mountaintops in central Mexico. The monarchs began arriving in the oyamel forests last November as immature individuals of the Methuselah generation. Their southward journey to Mexico began near the Great Lakes region of the northern United States and southern Canada.
What’s so fascinating about butterflies flying south for the winter? The monarchs, tiny and fragile insects, travel anywhere from 2,000 to 4,500 km during their migration, an unparalleled accomplishment. What is even more remarkable is that these monarchs have never been to their winter destination before. They’re the great-great-grandchildren of the generation that was there the previous winter. In addition, this is the only species known by the scientific community that has a generation, the Methuselah, that lives almost 10 times longer than any other generation. It would be like a generation of humans living to an age of 800-900 years old. All of these factors make for interesting biology – and for an interesting winter destination for the curious traveler.
Another striking aspect of this monarch migration is that the North American populations cover an area near the Great Lakes that spans 965,200 square miles. The 12-14 colonies that overwinter in Mexico only cover an area of 10-15 acres! As a well-known guide in Morelia noted, “That’s like fitting all of the gringos on the planet into the Super Bowl or all of the Muslims at Mecca”. In other words, you have a myriad of monarchs compressed into a relatively small area. There are so many butterflies hanging on the branches of trees that the branches bend – an extraordinary feat by an insect that weighs a fifth of a penny. I bet the butterfly predators (orioles, grosbeaks, and deer mice) see it as a monarch all-you-can-eat buffet.
Why do these monarchs fly so far to end up at cold mountains in Mexico when they’re running away from the pending cold to begin with? Why is it only the monarchs east of the Rockies that have a long-lived Methuselah generation exhibiting long distance migration? These are questions still being pondered by scientists. Regardless of the answer, you can be assured that witnessing monarchs at any of the butterfly reserves in Mexico is an experience of a lifetime and well worth the journey. An utterance of the word “wow” is guaranteed with the price of admission.