It’s early November and, monarchs have finally completed their migration! The ones who have beat all the odds and survived predators, parasites, storms and a 3,000 mile flight, are ready to rest for the winter months in the Transvolcanic Mountains of Mexico.
During winter, the normally solitary monarchs will roost in large groups to stay warm and maintain fat reserves they’ve accumulated from the fall, clinging tightly to each other in oyamel fir forests. These tiny, dwindling stands of trees provide a microclimate with ideal temperature, humidity, and elevation for monarchs to overwinter. On brief, sunny occasions, monarchs will venture off in search of water, never straying too far from the protective cover of the mature fir canopy.
Monarch populations are monitored during the winter months because their distribution is so widespread during the migration and breeding seasons. While breeding populations in late summer are much larger, many monarchs don’t survive the migration and therefore do not contribute to the next spring’s generation. NatureServe and The Xerces Society for Invertebrate Conservation estimate monarchs occupy about 1.65 acres of oyamel fir forests across 12 different locations, a sharp decline from the 50 acre stand used by wintering monarchs in the late 1990s. As many know, the populations have dropped significantly in the last 20 years. Last winter marked the smallest overwintering monarch population that has ever been recorded. There are many factor influencing the decline of monarch populations. The occurrence of episodic weather events and loss of summer breeding habitat contribute to declining numbers, while illegal logging and invasive species have fragmented and compromised the integrity of the oyamel forests in which the monarchs overwinter.
If this fascinating journey and tale of survival wasn’t interesting enough, the arrival of the monarchs coincides with a significant event in Mexican culture. October 31 marks the beginning of “El Dia de los Muertos” or Day of the Dead, a time when everyone comes together to celebrate and remember deceased family, friends, and ancestors. Monarchs arriving at the wintering grounds in Mexico this time of year are the “great grandchildren” of the monarchs that began the migration cycle in March of the previous year. Unlike their parents and grandparents that lived for several weeks, the migrating generation will live upwards of nine months as they overwinter in Mexico.
Day of the Dead coincides with the Christian holy days, All Hallows Eve, All Saint’s Day, and All Souls days which are celebrated October 31 through November 2. As Catholic traditions and indigenous cultures mixed, monarchs have come to represent the souls of loved ones returning to visit each year.