THURSDAY, Feb. 21 (HealthDay News) -- Global climate change could have a profound impact on the migration pattern of the monarch butterfly, according to a new study.
These butterflies, which fly 2,000 miles south from North America to the mountains of Mexico every fall and back again in the spring, would simply keep flying south if they didn't feel chilly winter weather, researchers found.
The study was published Feb. 21 in the journal Current Biology.
"The monarchs need the thermal microenvironment at the overwintering sites for the migration cycle to persist. Without that thermal stimulus, the annual migration cycle would be broken and we will have lost one of the most intriguing biological phenomena in the natural world," explained Steven Reppert of the University of Massachusetts Medical School, in a journal news release. "This increased understanding will help us protect the migration."
In an earlier study, the researchers revealed monarchs use skylight cues and an internal compass to help guide them in their migration south. In this new study, the researchers found these navigation tools also help the butterflies return north.
To determine what triggers the monarchs to change direction, they captured a sample of butterflies as they were about to begin their fall migration south. In the lab the butterflies faced the same changes in temperature and light they would experience naturally in the Mexican mountains.
After 24 days in the lab, the butterflies were released and headed north -- not south, the researchers noted. But the butterflies that were captured and kept warm continued to fly south.
The study's authors confirmed the change in the monarch's direction was because of the cold temperatures, not day length. They suggested their findings shed light on the biological processes involved in monarchs' migration.
The U.S. Environmental Prot
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