Each fall millions of monarch butterflies use a sophisticated navigation system to transverse 2,000 miles from breeding sites across the eastern United States to an overwintering habitat in specific groves of fir trees in central Mexico. Scientists at the University of Massachusetts Medical School and Worcester Polytechnic Institute have identified a new component of this complex system. They reported in Nature Communications that monarchs use a light-dependent, inclination magnetic compass to help them orient southward during migration.
