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BOB HIRSHON (host):
Magnetic migration. I’m Bob Hirshon and this is Science Update.
Every fall, millions of monarch butterflies migrate two thousand miles from Canada and the US to central Mexico. At this year’s Society for Neuroscience meeting, University of Massachusetts Medical School neurobiologist Steven Reppert discussed how the butterflies, like birds and sea turtles, use Earth’s magnetic field to navigate.
STEVEN REPPERT (University of Massachusetts Medical School):
It’s the first evidence that I’m aware of in a long distance migratory insect… that it’s been shown to use the Earth’s magnetic field in this way, for a sense of direction.
Monarchs primarily use cues from the sun, but Reppert discovered that on cloudy days they rely on the geomagnetic field, which varies as one moves away from the poles. Their antennae pick up both the sun’s position and the magnetic field’s angle, providing compasses that keep them on course, no matter the cloud cover. I’m Bob Hirshon, for AAAS, the science society.