The Monarch's Journey NORTH?
Analyzing Spring Monarch Migration Patterns

Background

How far from Mexico — and in what direction — does the monarch migration advance in the spring?

Imagine drawing the leading edge of the migration at different stages as the monarchs move across the Continent. Such a line is called an "isopleth". ("Isopleth: A line on a map connecting points at which a given variable has a specified, constant value." The "given variable" would be "FIRST Monarch" and your "constant value" must be a certain date.) Using this spring's monarch data, you can draw the wave (an isopleth) at regular time intervals to show the migration's advance.

Activity

1. On the map above, look at the color-coded key we use to show the date each monarch was seen. Notice that the colors change every two weeks. (Click on face of map to enlarge.)

2. Print a color copy of migration map.

3. First draw a line to show how far the migration had progressed by March 15. To do this, connect those white dots that are the farthest from the Mexican sanctuaries.

4. How far had the monarchs progressed two weeks later? Chose a different color marker and connect those yellow dots that are the farthest from Mexican sanctuaries. This lines shows how far the migration had moved as by March 28.

5. Every two weeks, when the color changes, print out a new monarch migration map. Chose a new color marker to draw the line of advance. For each changing color, connect those dots that are the farthest from Mexican sanctuaries. Save these maps, because it gets difficult to see the waves when more sightings are added. Keep notes about your thoughts on the back of each map.

6. Consider the factors that might influence the migration. Draw upon other resources, such as weather, climate and vegetation maps.

 Weather and Climate Maps Plant Hardiness Zones Map

7. Finally, at the end of the season, summarize all the changes you saw.

Discussion Questions

• Describe the pattern you noticed every two weeks. In what ways did the pattern change during the spring season?
• Does the monarch migration truly move northward? Explain what direction(s) the monarchs moved and why you think this was so.
• How would you fill in the blank? "The spring monarch migration advances at the average rate of about ___ miles per week."
• Why is it so important to take into consideration the distance the monarchs have flown from Mexico when you analyze the pattern?
• What made this study difficult? How would you change it if you were to do it again?

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