Mountain Geography
Focuses the Monarch's Migration in Mexico
Field Notes Contributed by Dr. Bill Calvert


October 17, 2004
Cumbres de Monterrey, Nuevo Leon, Mexico

Cienegas de Gonzales is butterfly junction. It was very curious traveling toward the mountains. We weren’t seeing that many. We were seeing an occasional monarch. There’s something about that mountainous area, where the mountains turn from an easterly direction to a southeasterly or a south-south easterly direction, that focuses the monarch migration.

This is a part of the Sierra Madre that is quite high. I believe some of the mountains go up to 9000 feet in this area. The ridges are very, very sharply defined, and they curve distinctively.

They change direction. It’s just absolutely phenomenal to see from the air. They change directions from roughly an easterly direction, running from Saltillo to Monterrey. And at Monterrey they make this bend and they turn toward Linares. And the butterflies follow that bend. So if you go to Huasteca Canyon, for example, which is a cut in the range, you can find them flying due east. And when you get down to Linares, they’re flying south, southeast.

There's something about the mountains that’s guiding them.


Listen to Dr, Calvert 

Image by NASA
"At Monterrey, the Sierra Madres Mountains make a southerly bend. The monarchs follow the bend."