MEXICO CITY (AP) -- Scientists have discovered genetic information that helps explain how monarch butterflies find their way from Canada to winter nesting grounds in the mountains of Mexico.

The study, published online Tuesday in the PLoS Biology Journal and the Public Library of Science, found that the butterflies' biological clocks help them use the sun as a compass.

Dr. Steven Reppert, the University of Massachusetts neurobiologist who led the study's seven-member research team, said monarch butterflies have unique circadian clocks, which regulate daily activities like sleep and hunger.

The researchers genetically mapped the molecular underpinings of the butterflies' circadian clocks and found cryptochrome proteins common in both insects and mammals. Reppert believes these proteins enable the monarchs to navigate using the sun's position in the sky.

"A butterfly's brain is no bigger than the head of a pin, and yet it has this incredible capability. So we really want to understand that," Reppert said.

When understood completely, the find might help shed light on the biological clocks of humans, and in turn aid research into everything from sleep disorders to depression.

Lincoln Brower, a monarch expert at the University of Florida and Sweet Briar College in Sweet Briar, Virginia, said the discovery was significant because it shows that "studying the monarch butterfly is producing crucial information about the nature of life."

The research was funded in part by grants from the National Institutes of Health and the Czech Republic's Ministry of Education, Youth and Sports.

--Traci Carl, The Associated Press