Colony Formation Continues on Cerro Pelón

The Cerro Pelón Chronicles: A Butterflies & Their People Project

November 8–12, 2017

Citizen scientist observations inform much of what we know about monarch butterflies’ annual 3,500-mile migration from Canada to Mexico. But during the monarchs’ five-month-long stay in Mexico, very little information their timing, location and behavior reaches the public. (I talk about some of the reasons why here.) This series is an effort to fill that gap and connect our on-the-ground citizen science and conservation efforts with monarch lovers everywhere.

In the Cerro Pelon Sanctuary, three forest rangers employed by the State of Mexico (CEPANAF) spend all day every day observing and protecting the monarch colony. Recently they were joined by three Butterflies & Their People arborists, a forest protection and monitoring project made possible by our partnership with the Monarch Butterfly Fund. The arborists took the photos for this piece, while CEPANAF Ranger Pato Moreno recorded these observations about the second week of butterfly season 2017–18. (Click here to read about week one.) -E.S.

Butterflies & Their People arborists Carmelo and Pancho in El Llano de 3 Gobernadores on Cerro Pelon, State of Mexico. This season’s colony is forming up on the mountain behind them. Photo by Pato Moreno.

Butterflies & Their People arborists are monitoring the nectar sources near the monarch butterfly colony on Cerro Pelon. As climate change pushes average temperatures up, the monarchs have become more active across the season. Last season we witnessed flight activity almost every day: their state of semi-hibernation seems to be a thing of the past. They will need to eat more to compensate.

On Saturday the Butterflies & Their People arborists and I went hiking to another part of the mountain to see another colony we’d heard about. The butterflies were clustered in even more trees than in the colony that has formed above El Llano, but this area isn’t open to the public. I think it’s good that there are some colonies that are always left alone — that way we can make sure there are always butterflies around to make the trip back north.

Secret colony not open to the public on Cerro Pelon. On 11/11/17 monarchs covered an estimated 50 trees.

On our way back to El Llano, we passed by another roost of monarchs, but as soon as they sensed our presence they started flying out of their trees. We kept our distance, so as not to startle them any more than we already had.