Magnetic Compass Guides the Autumn Migrations of the Monarch Butterfly

Thank the monarch butterfly for its unfaltering sense of direction. These insects can fly on even the cloudiest of days with the help of a magnetic compass that directs their migration, according to a recent study published in the journal Nature Communications.

Like migratory birds and sea turtles, some scientists had held a sneaking suspicion that the monarch butterfly also uses a magnetic compass to guide its journey. In the fall, as millions of monarchs fly in from North America to prepare their trip towards the Michocán mountain ranges in central Mexico, they look towards a sun compass to light their path, according to researchers from the University of Massachusetts.

The monarch, characterized by its orange-and-black wings, holds light-sensitive antennae magnetosensors that help them easily find their way south.

To test the insect's co-reliance on a magnetic compass, biologists from the university placed monarchs in a flight simulator that was surrounded with different artificial magnetic fields to help test the creatures' directional instincts.

In the beginning of the study, most headed towards the equator. However, they soon turned north when the inclination angle of the magnetic field was reversed. The compass also only worked in the presecent of light at the upper edge of the visible light spectrum, according to phys.org.

"Our study reveals another fascinating aspect of monarch butterfly migratory behaviour," the authors wrote, in a news release. "Greater knowledge of the mechanisms underlying the fall migration may well aid in its preservation, currently threatened by climate change and by the continuing loss of milkweed (plant) and overwintering habitats.

"Another vulnerability to now consider is the potential disruption of the magnetic compass in monarchs by human-induced electromagnetic noise, which can apparently disrupt geomagnetic orientation in a migratory bird."