Learn fun facts about monarch butterflies!
How does temperature affect monarchs?
In winter, the temperature must be just right for monarchs to survive. If temperatures get too warm, monarchs will use up their stored fat too quickly, and can get very weak or die. If temperatures get too cold (below 55 degrees Fahrenheit), the butterflies can become paralyzed. (Click here to see a graph of seasonal temperatures at monarch wintering grounds in Mexico.)
Monarchs stay safe from cold by huddling together in “clusters” in the trees. The forests in Mexico and California, where monarchs spend winter, also provide protection from weather. The trees act as insulation from the cold and lessen the effects of wind and rain. Like people, they shiver to warm their muscles when they are cold. (Click here to see a video of shivering monarchs.)
In the spring and summer, monarchs need warm temperatures for migrating and mating. However, they usually don’t live in temperatures above 95 degrees Fahrenheit!
Adult Monarchs Clustered On a Branch. Courtesy of U.S. Fish & Wildlife Service.
- Monarchs are poisonous! Monarch caterpillars eat milkweed plants, which contain a toxic chemical that stays in the caterpillar even after it turns into an adult. This is one way monarchs stay safe from predators.
- Monarch butterflies need moisture to survive during winter. They drink the dew from nearby fields, or morning mist that settles onto the trees where they cluster.
- Scientists use radar (called vertical-looking radar) to monitor the migration of monarchs and other insects that fly in high-altitude winds. This tool is similar to the radar used by meteorologists to monitor weather.
- Weather plays an important role in monarch survival. In January 2002, a severe rain storm followed by below-freezing temperatures killed nearly 80% of the monarch population (250 million adult monarchs!) wintering over in El Rosario butterfly sanctuary in Mexico.
- Monarchs are the only butterflies that do a two-way migration like birds. The difference between bird migration and monarch migration is that monarch migration is generational. The monarchs that migrate south in the fall are not the same butterflies that return in the spring: their children and grandchildren do!
Map of Fall Monarch Migration.
Map of Spring Monarch Migration.
Maps Courtesy of U.S. Geological Survey National Atlas.