Each year, the monarch butterfly migrates up to 3,000 miles to its wintering range in Mexico. They’re the only butterfly known to make a two-way migration, which is usually more associated with bird species. What’s behind such a monumental feat? A new study may have some answers.
University of Georgia researchers recently conducted a study to see if the monarch’s wing coloring had any impact on its flight or migration. Their findings, published in the journal PLOS One, suggest that butterflies with bigger white spots may have a migratory advantage.
Andy Davis, lead author and assistant researcher at UGA’s Odum School of Ecology, explains, “We undertook this project to learn how such a small animal can make such a successful long-distance flight. We actually went into this thinking that monarchs with more dark wings would be more successful at migrating because dark surfaces can improve flight efficiency. But we found the opposite.”
They came to this conclusion after a study involving nearly 400 monarch wings collected at different spots along their migratory route. After examining them, the researchers found that butterflies with more white pigment – roughly 3% more – and less black (about 3% less) were more apt to successfully reach their destination. There was another color-related finding, too. When studying museum specimens, the team found that migratory monarchs had substantially larger white spots, compared to their wing area, than most non-migratory butterflies.
The researchers say this indicates that each year, those with large white spots survive the trip, meaning they’ll live to reproduce and pass on those genes. However, climate change and its increasing heat and solar energy may impact the species’ flight, as well as any adaptions they’ve made for dealing with the radiation exposure during the long journey.
Davis says, “The amount of solar energy monarchs are receiving along their journey is extreme, especially since they fly with their wings spread open most of the time. After making this migration for thousands of years, they figured out a way to capitalize on that solar energy to improve their aerial efficiency…
“With greater solar intensity, some of that aerial efficiency could go away. That would be yet one more thing that is hindering the species’ fall migration to Mexico.”
The researchers say further study is needed to confirm how the white spots help the monarch in their migration to their wintering habitat.
Did you know that you’ve helped ensure they have a healthy habitat when they reach their destination? Click here to learn how! If you’d like to do more to aid in the species’ survival, consider helping us plant milkweed, the monarch’s favorite flower!