Monarch Butterfly Biosphere Reserve

Oyamel forest where every eastern monarch in North America spends the winter

The Monarch Butterfly Biosphere Reserve covers 56,000 hectares of mountain forest straddling the states of Michoacán and México. From late October through March, the reserve hosts an estimated 100–300 million monarch butterflies that have migrated from Canada and the northern United States to spend the winter in the oyamel fir forests at altitudes between 2,400 and 3,600 metres.

The El Rosario sanctuary is the most accessible and largest of the colonies open to visitors. You hike uphill (or ride on a local horse) through increasingly dense forest until you reach the winter cluster — a vast orange and black canopy covering the trees in every direction. When the sun warms the hillside in mid-morning, millions of butterflies take flight simultaneously. The sound is remarkable: a soft rushing, like rain, as their wings beat the air.

The sanctuary is open daily during the season. Entry fees go partly to the local ejido communities who protect the forest. Hire a local guide at the entrance — they know where the main clusters are, which changes from year to year. Dress warmly; the altitude and shade make it cold even when the valley below is warm.

Guide

Activities

There is one activity here and it lasts from late October to March. Outside those months the forest is empty and the sanctuaries are shut.

Four colonies are open to visitors. El Rosario, above Ocampo in Michoacán, is the largest and busiest; Sierra Chincua, nearer Angangueo, is quieter and the walk is gentler; Cerro Pelón and El Capulín, on the Estado de México side, are the least visited and the hardest to reach. All of them sit between 2,400 and 3,600 metres, and the air at that altitude is thin and cold in the shade even when the valley is warm.

Go between eleven and two. The butterflies cluster on the oyamel trunks overnight in great brown masses and do not move until the sun reaches them; when it does, they lift off in their millions, and the sound — a soft rushing like distant rain — is the thing people remember. Arrive at nine and you will see bark.

Entry is by local guide, which is not optional and is the point: the forests are owned by the ejidos who stopped logging them, and the guide fees and entrance money are what makes protecting the trees worth more than cutting them. Guides are hired at the gate and know where the colonies have settled, which moves from year to year.

Horses are available for the climb at El Rosario and Sierra Chincua. Do not touch butterflies on the ground, and stay on the path — a good proportion of the ones underfoot are alive.

A story
Every monarch butterfly east of the Rocky Mountains that survives the summer in Canada and the northern United States ends up here. They navigate over 4,000 km using a combination of the sun, the Earth's magnetic field, and an internal clock — and they have never made this journey before. Their parents died on the way back north. Yet generation after generation arrives at the same oyamel fir forests in the mountains of Michoacán.