Fall Migration: Too Cold to Fly Today?
Monarch butterflies are in a race against time during fall migration. They must leave the north before they're trapped by the cold. In order to fly, a monarch's muscles must be warm enough. In fact, if a monarch's thoracic (body) temperature is below 55 F (13 C) it can't fly at all.
| This map shows how quickly temperatures drop as the fall season progresses. The days are getting colder (and shorter, too)! With each passing day, monarchs have a smaller and smaller window of time in which they can fly. |
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Migrating monarchs don't fly at night. They can only continue their journey south when their temperature is above 55 degrees F.
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Predict: Will monarchs be able to fly today in your hometown? What time in the morning will they be able to lift off? What time in the evening must they come down to rest? How many hours do you predict monarchs could fly between sunrise and sunset today? (See: sunrise/sunset look-up.)
- Measure
the outside temperature every hour during the school day. Is
it above or below 55 degrees F? If it goes above 55 F, for how many
hours does it stay there?
- Think! Between sunrise and sunset, how many hours could monarchs have flown? During how many hours was it too cold for them to fly? How did this compare with your predictions?
Extensions
- Continue gathering data as the season continues. Each day, check the previous day's temperatures. Go to weather.com. Put in your zip code. Choose "yesterday" from the menu and then choose "hourly reports." (You'll find times and temperatures in the lefthand columns.) Make a graph that shows how many hours in each 24-hour day the temperature is above (or below) 55 F.
- Predict where in the country monarchs will be able to fly today or this week. Use this interactive map.
