"For migratory monarchs, the inclination compass may serve as an important back up system when daylight cues are unavailable, the researchers said."
New York, June 25 - If you thought that only humans use a magnetic compass to know the direction, you will be surprised to know that even butterflies use compass, according to new research.
Each autumn, millions of monarch butterflies use a sophisticated navigation system to transverse 2,000 miles from breeding sites across the eastern United States to a new habitat in central Mexico.
Monarchs use a light-dependent, inclination magnetic compass to help them orient southward during migration, the findings showed.
Our study reveals another fascinating aspect of the monarch butterfly migratory behaviour, said senior study author Steven Reppert from the University of Massachusetts Medical School in the US.
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 over-wintering habitats, he added.
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, said co-author Robert Gegear, assistant professor of biology and biotechnology at Worcester Polytechnic Institute in the US.
Monarchs use a time-compensated sun compass in their antenna to help them make their 2,000 mile migratory journey to over-wintering sites.
During the absence of daylight cues, such as under dense cloud cover, migrants have been, surprisingly, seen flying in the expected southerly direction.
Given the ability of monarch cryptochromes (CRY), a class of proteins that are sensitive to ultraviolet A/blue light, to restore a light-dependent magnetic response in CRY-deficient Drosophila, Reppert and colleagues suspected that monarchs also possessed a light-dependent magnetic compass.
For migratory monarchs, the inclination compass may serve as an important back up system when daylight cues are unavailable, the researchers said.
The findings were published in the journal Nature Communications.