Letter From Pato Moreno: Monarchs Quick to Form a Colony on Cerro Pelon


Published: 11/10/2021

By CEPANAF Ranger and Butterflies & Their People Supervisor Pato Moreno

The first butterflies reached the summit of Cerro Pelón on October 30. For three days, they just hovered around the mountain. On October 31 it was rainy and chilly. By November 3, the monarchs began to form a colony in Carditos. That day we saw 12 trees filled with butterflies. The cold continued, but thank goodness, the rain stopped. On Thursday the 4th, we observed a massive arrival of butterflies. That afternoon, we counted more than 40 trees. Among these, 15 were densely laden with butterflies. We think the ones that were more spread out are saving a space for the butterflies that are still on the way. We went to check the place where they roosted last year, but there were no clusters to be found El Llano de los Tres Gobernadores.

Compared to last year, when the temperatures were higher and the monarchs were constantly shifting locations, the butterflies seem very determined about forming their colony this season. It reminded us of seven years ago, when my colleagues and I first took over the ranger jobs from our fathers, and the butterflies arrived and settled in very quickly. This behavior seems to be caused by the weather, which is cool and cloudy (50-53°F). It seems unlikely that they will move any time soon—I hope that what we’re seeing now represents a stable colony.

Watch a video from 2020 of a colony forming at Cerro Pelon: https://vimeo.com/643981446/2099cfc465

*If you’d like to learn more about forest protection in the Monarch Butterfly Biosphere Reserve, Journey North has collected a few articles to inspire discussion:


Read the Spanish version of Pato Moreno’s letter»