Monarch butterflies are famous for their remarkable annual migration, traveling 2,000 miles from eastern United States to central Mexico every autumn. Now researchers have determined that these butterflies find their way much like some birds do, using an internal magnetic compass.
A study published in the journal Nature Communications details how researchers from the University of Massachusetts and Worcester Polytechnic Institute identified the use of a light-dependent inclination magnetic compass in migrating monarchs.
The insects with their characteristic orange-and-black wings flutter thousands of kilometers each year from the United States and southern Canada to the Michoacan Mountains in central Mexico where they overwinter. The butterflies, whose Latin name is Danaus plexippus, have long been known to use a type of solar compass in the brain. Yet, curiously, they are also able to migrate when skies are heavily overcast which suggested co-reliance on a magnetic compass.
Monarch butterflies have a keen sense of direction even on cloudy days. This is because they have a magnetic compass to direct their migration in addition to navigating by the position of the sun, researchers report today in a Nature Communications study. Scientists have long known monarch butterflies to navigate by a sun compass, meaning they use the position of the sun to determine which way is south.
“In the fall, millions of monarchs from all along the northeastern corridor of the U.S. to Canada migrate to the Michoacán mountain range in central Mexico, crowding together so densely that the air is filled with butterflies, said monarch butterfly expert and University of Minnesota professor,” Karen Oberhauser.
The research published in the journal Nature Communications, sees the monarch join a lengthening list of birds, reptiles, amphibians, turtles and insects, including honeybees and termites, believed to use the magnetic field for navigation.
“Our study reveals another fascinating aspect of monarch butterfly migratory behaviour,” the authors wrote.
“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.”