Chincua, Mexico, Nov 28 (EFE).- By Diego Cubillas Sierra
Every year, in the Mexican state of Michoacán, at an altitude of over 3,300 meters (10,830 feet) in Sierra Chincua, millions of monarch butterflies return after traveling 4,000 kilometers (2,485 miles) from Canada to the Mexican forests where they hibernate.
This migratory phenomenon, which according to the state governor Alfredo Ramírez Bedolla, represents “the souls of our loved ones being carried away,” was officially recorded for the first time in 1975 and remains a mystery to experts.
“There are several hypotheses. The butterflies have been examined, and structures related to the detection of certain metals or minerals found in the mountain range where they arrive have been found in their brain equivalent part,” Javier Ponce Saavedra, an entomologist at the Michoacana University of San Nicolás de Hidalgo, told EFE on Friday.
Another, more widespread hypothesis is that “there is evidently biological information in their genes that obliges them to follow the route their ancestors followed,” he added.
Ponce explained that a research group in the United States uses chips placed on the insects’ bodies to geolocate them on their journey; there are at least two hibernation refuges in the US.
The expert indicated that there are two types of butterflies, those that migrate and those that do not. What seems to be the key is the migratory generation: “The butterflies that have a different generation and stronger larvae.”
“The caterpillars store a large amount of energy so that, when the adult emerges, it has enough strength to begin the flight to its hibernation site. Those that arrive do so not only to reproduce but also to spend the cold season,” he affirmed.
Threats to migration and solutions
Although millions of monarch butterflies can be seen in oyamel and pine forests, the species faces threats and is part of the Red List of endangered species of the International Union for Conservation of Nature.
The annual monitoring of the forest area occupied by the colonies in Mexico reached its lowest level in 2013, with only 0.67 hectares recorded. In 2024, experts reported 0.9 hectares of coverage.
“The construction of roads or human-carried out modification processes has strongly reduced milkweed populations (the plant the butterflies feed on), which can cause a decrease in butterfly populations. Another cause is the application of insecticides along their route,” Ponce explained.
Thermal variations caused by climate change, as well as deforestation and illegal logging, pose a threat to the insects’ journey.
Ponce highlighted the importance of “tripartite cooperation between governments so that the route is protected regardless of borders,” thereby ensuring the safety of the butterflies during hibernation and migration.
This natural phenomenon has become a tourist attraction. Between Nov. 2025 and Mar. 2026, it is expected to receive over 800,000 visitors, generating an economic impact of over 1 billion pesos (approximately 54 million dollars), as announced by the Secretariat of Tourism, Josefina Rodríguez Zamora.
Visitors can access the five sanctuaries in Sierra Chincua, Senguio, El Rosario in Michoacán, Piedra Herrada, and San Mateo Almoloya in the State of Mexico every day up until Mar. 30, 2026. EFE
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