Monarch butterflies use internal compass for epic migration

Earth.com highlighted a new study by the University of Cincinnati that found monarch butterflies have an internal compass for its epic migration that flips when the temperatures plunge.

This changing polarity helps butterflies prepare for the return trip on their migration back and forth across North America.

The study was published in the journal PLOS One.

UC Associate Professor Stephen Matter, former UC Assistant Professor Patrick Guerra, now at the North Carolina Department of Environmental Quality, and UC graduate student Samuel Shively-Moore helped explain how monarchs navigate over thousands of miles on their way from their northern range as far away as Canada to their overwintering roosting sites in the mountains of central Mexico.

Monarch primarily use a sun compass calibrated to the number of hours of daylight as a compass. But monarchs also use a magnetic compass to stay the course. 

But researchers found that butterflies exposed to 24 days of cold temperatures like the kind they experience in their overwintering grounds reorient to the north, suggesting their internal compass is recalibrated by the cold.

“Our discovery that coldness triggers the northward flight direction in spring re-migrants solves one of the long-standing mysteries of the monarch migration,” Guerra told Earth.com.

Their findings raise questions about how rising temperatures might affect the monarchs' navigational cues.

Featured image at top: UC biologists are unlocking secrets of the monarch butterly's epic migration. Photo/Michael Miller