Mexican Overwintering Monarchs Graph
This graph shows the area of forest occupied by colonies of hibernating monarchs in Mexico from 1994-2016 (Graph courtesy of Ernest Williams). In late January 2015, the World Wildlife Fund in Mexico reported that the size of the 2014–2015 overwintering population is the second smallest since monitoring began in 1994, occupying an estimated area of just 1.13 hectares (2.79 acres) (Secretariat of Environment and Natural Resources, Mexico 2015). Over the last 21 years, the average forested area occupied by monarchs at the Mexican overwintering sites has been 6.00 hectares (14.82 acres). Researchers estimate that between 10–50 million monarchs exist per hectare. Thus, the size of 2015’s population represents only 19% of the 20-year average.