The Migration Through Mexico
A Navigation Mystery

Where Monarchs Probably Go
The map below shows the path the monarchs probably take as they migrate across Mexico. We say probably because scientists don't know for sure. Few people have traveled the route during migration, the area is vast, and the monarchs can move quickly and high overhead, and the English/Spanish language barrier makes communication difficult. This map is based on the limited observations made by biologist Dr. Bill Calvert--and many others--during fall migration.

Part of the Mystery: Why Don't They Fly Straight South?
The monarch's winter home is directly south of the region in Texas (centered on Del Rio) where most monarchs cross the border into Mexico. However, the monarchs don't travel straight south as they cross Mexico. Study the map and notice the way the monarchs travel instead. Compare the line of longitude -100 West to the path of the migration and you'll see this clearly. Look carefully at the map and think, why don't the monarchs travel straight south as they cross Mexico? The direction the monarchs travel is "delightfully confusing!" says Dr. Calvert. Their route is a mystery of monarch navigation.

Why not fly straight south?
Click to see larger map.