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.