Every year monarchs migrate to Mexico from across eastern North America. They cluster by the millions in 12 mountain sanctuaries. Because the butterflies are gathered in one small region of Mexico, scientists have a chance to estimate the size of the entire migratory population once each year.

Resources: Explore authentic data through graphs and maps.

1. Explore how scientists estimate the size of the monarch population in Mexico's overwintering region each year.

2. Investigate questions about why monarch population studies are important; how scientists use the data to reflect on past events, assess current trends, and make predictions for the future.