It is perhaps the quietest animal migration on earth, so quiet in fact that until the 1970s no one even knew it happened. Every fall monarch butterfly populations of the United States and southern Canada head south to overwintering sites in Mexico. They go in search of food and warmer climes, a migratory journey that can take these delicate creatures two months to complete. Some will have traveled 3,000 miles, a seemingly formidable task for such a small and delicate a creature as a butterfly.Then, each March the next generations of monarchs return north, arriving home in July, having flown 50 to 100 miles every day for several weeks helped only by the wind and their fat reserves. It is the only butterfly known to perform such a migration, more likely seen in birds and larger animals, and although monarch butterflies can be found across the globe, the great North American migration is carried out by just one subspecies increasingly threatened by habitat loss and disease.
The great North American migration: a butterfly extravaganza