Monarch Conservation Toolbox

International Monarch Monitoring Blitz

From July 27 to August 4, 2019, citizens from Canada, Mexico and the United States will join the International Monarch Monitoring Blitz (the Blitz) to help identify the monarch butterfly’s breeding sites that are essential to its survival.

To learn more and take part in the Blitz:


The International Monarch Monitoring Blitz aims to provide a valuable snapshot for scientists of monarch population status across the monarch migration paths in Canada, Mexico, and the United States.

The Blitz is an initiative from the Trinational Monarch Conservation Partnership, created through the Commission for Environmental Cooperation.

Each country has something to learn from monitoring monarchs during the same time period, and comparing these observations year-to-year. Observations reported in Canada and the northern United States provide scientists with a snapshot of the peak breeding monarch population and the presence of milkweed. Reports from the southern United States document whether early migration and breeding are occurring. Data collected in Mexico document any monarch breeding taking place in traditionally migratory areas.

This Blitz is organized by:

Sites monitored during the Monarch Blitz (2018)

    Summary of the 2018 International Monarch Monitoring Blitz
  • 486 participants across Canada, Mexico, and the United States
  • 53,588 milkweed plants monitored
  • Surveys completed in 36 US states, 7 Canadian provinces and 16 Mexican states
  • 13,796 monarchs observed
    • 6,905 eggs
    • 4,900 caterpillars
    • 470 chrysalises
    • 1,521 butterflies