Monarch butterflies employ `magnetic compass` during migration

Researchers have claimed that monarch butterflies use a light-dependent, inclination magnetic compass to help them orient southward during migration.

ANI| Updated: Jun 25, 2014, 14:26 PM IST

Washington: Researchers have claimed that monarch butterflies use a light-dependent, inclination magnetic compass to help them orient southward during migration.

Senior study author Steven Reppert, MD, the Higgins Family Professor of Neuroscience and distinguished professor of neurobiology at UMass Medical School, said taken as a whole, our study reveals another fascinating aspect of the monarch butterfly migratory behavior, adding "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 and overwintering habitats."
He said, "A new vulnerability to now consider is the potential disruption of the magnetic compass in the monarchs by human-induced electromagnetic noise, which can also affect geomagnetic orientation in migratory birds."

Co-author Robert Gegear, PhD, assistant professor of biology and biotechnology at WPI, explained, "Our study shows that monarchs use a sophisticated magnetic inclination compass system for navigation similar to that used by much larger-brained migratory vertebrates such as birds and sea turtles."
Monarchs use a time-compensated sun compass in their antenna to help them make their 2,000 mile migratory journey to overwintering sites. During the absence of daylight cues, such as under dense cloud cover, migrants have been, surprisingly, seen flying in the expected southerly direction. It`s been hypothesized that monarchs use geomagnetic cues to help navigate when day light cues are unavailable to them during migration.

Using flight simulators equipped with artificial magnetic fields, Patrick Guerra, PhD, a postdoctoral fellow in the Reppert lab, examined monarch flight behavior under diffuse white light conditions. He found that tethered monarchs in the simulators oriented themselves in a southerly direction. Further tests in the simulator revealed that the butterflies used the inclination angle of Earth`s magnetic field to guide their movement. Reversing the direction of the inclination caused the monarchs to orient in the opposite direction, to the north instead of the south.

The study has been published in the journal Nature Communications.