Monarch Butterfly Biosphere Reserve – El Capulin Sanctuary in the State of Mexico

The Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage Site in Mexico, covers 56,259 hectares of rugged, forested mountains approximately 100 km northwest of Mexico City. The reserve is located along the border of the states of Michoacán and Mexico.  Scientists estimate that between 60 million and 1 billion monarch butterflies overwinter in the reserve.  These individuals have migrated from the Great Lakes Region in the US and Canada to overwinter from October through March in oyamel fir (Abies religiosa) forests in Mexico.

The reserve includes eight colony sites.  Five colonies are located in Michoacán State and the other three in Mexico State.  Sierra Chincua and El Rosario in Michoacán and El Capulin, Piedra Herrada, and La Mesa in Mexico are open to visitors.

The following series of photos was taken on March 6, 2014 at El Capulin Sanctuary during a Reefs to Rockies trip organized in association with Denver Botanic Gardens.

Reefs to Rockies El Capulin Monarch Sanctuary Mexico eco tours
Entrance at El Capulin Monarch Butterfly Sanctuary in Mexico State. Copyright Reefs to Rockies.
El Capulin monarch butterfly sanctuary mexico eco tour
Entrance at El Capulin Monarch Butterfly Sanctuary in Mexico State. Copyright Reefs to Rockies.
El Capulin Monarch sanctuary Mexico eco tour
Gearing up for the ride to the butterfly site. The monarchs move altitudinally throughout the winter and they had moved down in elevation this week to about 9,000 ft. It was still 4.5 km of steep terrain to their location. Copyright Reefs to Rockies.
El Capulin monarch butterfly sanctuary Mexico eco tour Reefs to Rockies
Some members of the group decided to hike much of the way to the butterflies. Copyright Reefs to Rockies.
El Capulin monarch butterfly sanctuary Mexico eco tour Reefs to Rockies
We started seeing butterflies after about half an hour on the trail. They were feeding in open areas with flowers. Copyright Reefs to Rockies.

El Capulin monarch butterfly sanctuary Mexico eco tour Reefs to Rockies

El Capulin monarch butterfly sanctuary Mexico eco tour Reefs to Rockies
Monarch butterflies clustered on the trunk and branches of an oyamel fir. Copyright Reefs to Rockies.
El Capulin monarch butterfly sanctuary Mexico eco tour Reefs to Rockies
Monarch butterflies clustered on the trunk of an oyamel fir. Copyright Reefs to Rockies.
El Capulin monarch butterfly sanctuary Mexico eco tour Reefs to Rockies
Even though a single monarch butterfly weighs less than a gram, their collective weight bends branches of the oyamel fir. Copyright Reefs to Rockies.
El Capulin monarch butterfly sanctuary Mexico eco tour Reefs to Rockies
This time of year marks the beginning of mating season for the monarchs. Pregnant females are the ones that will make the journey north soon. Most male butterflies die at their wintering sites in Mexico. Copyright Reefs to Rockies.