Monarch Butterfly Forest Occupation at the Mexican Overwintering Sites: A New Reality

The history of the monarch butterfly conservation in Mexico began with the leadership of Lincoln Brower, William Calvert, Leonila Vázquez, and Héctor Pérez. This occurred after the discovery of the overwintering colonies by Catalina Aguado and Kenneth Brugger in 1975 and reported by Fred Urquhart in 1976. Four decrees by the Mexican government were needed to reach the current geographical protection of the Monarch Butterfly Biosphere Reserve (MBBR). The Monarch Region includes the MBBR and other three federal protected areas where 23 colonies have formed in 13 sanctuaries. From 2004 to 2022, when the National Commission of Natural Protected Area and WWF-Mexico have systematically coordinated the monitoring of overwintering colonies, the historical average area occupied by overwintering monarch colonies was 3.25 (± 1.75 SD) hectares (ha). In this chapter, we used the range derived from the mean estimated from the last 19 years, namely, 1.5 to 5.0 ha, as the range of the area occupied by monarchs overwintering in Mexico. This range represents the new reality of monarch occupation in Mexico as compared to the range recorded from 1993 to 2003 (average 8.82, ±4.02, range 4.8–12.8). Estimates within the current range should be considered normal. The keystone for the conservation of the overwintering monarch butterfly habitat in Mexico is the participation of local communities at the overwintering sites, the private sector, the organized civil society, and the three levels of government.